Nanomedicines for the Prevention and Treatment of Infectious Diseases (AAPS Advances in the Pharmaceutical Sciences Series, 56) 3031390199, 9783031390197

Citation preview

AAPS  Advances in the Pharmaceutical Sciences Series  56

Vandana B. Patravale Abhijit A. Date Anil B. Jindal  Editors

Nanomedicines for the Prevention and Treatment of Infectious Diseases

AAPS Advances in the Pharmaceutical Sciences Series Volume 56

The AAPS Advances in the Pharmaceutical Sciences Series, published in partnership with the American Association of Pharmaceutical Scientists, is designed to deliver volumes authored by opinion leaders and authorities from around the globe, addressing innovations in drug research and development, and best practice for scientists and industry professionals in the pharma and biotech industries. Indexed in Reaxys SCOPUS Chemical Abstracts Service (CAS) SCImago EMBASE

Vandana B. Patravale  •  Abhijit A. Date Anil B. Jindal Editors

Nanomedicines for the Prevention and Treatment of Infectious Diseases

Editors Vandana B. Patravale Department of Pharmaceutical Sciences & Technology Institute of Chemical Technology (Elite status), Deemed University Matunga, Mumbai, India

Abhijit A. Date Department of Pharmacology and Toxicology R. K. Coit College of Pharmacy University of Arizona Tuscon, AZ, USA

Anil B. Jindal Department of Pharmacy Birla Institute of Technology and Science Pilani Jhunjhunu, Rajasthan, India

ISSN 2210-7371     ISSN 2210-738X (electronic) AAPS Advances in the Pharmaceutical Sciences Series ISBN 978-3-031-39019-7    ISBN 978-3-031-39020-3 (eBook) https://doi.org/10.1007/978-3-031-39020-3 Jointly published with American Association of Pharmaceutical Scientists © American Association of Pharmaceutical Scientists 2023 This work is subject to copyright. All rights are reserved by the Publishers, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publishers, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publishers nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Editorial Contact: Charlotte Nunes This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Paper in this product is recyclable.

Preface

Microorganisms are ubiquitous in nature, and they play an essential role in the ecological balance. While many have no harmful effects on humans, and some are even beneficial, others can lead to severe infectious diseases. The human race has witnessed several deadly outbreaks of infectious diseases in the past century, starting with the Spanish flu in 1918, which claimed the lives of millions of people. Since then, there have been many other pandemics, such as the Asian flu (1957), Hong Kong flu (1968), SARS (2002), MERS (2012), and Ebola (2013), which have caused immense suffering and loss of life worldwide. The recent COVID-19 pandemic has highlighted the enormity of the challenges we face in preventing and treating infectious diseases, and it has disrupted economies and societies worldwide. Despite the remarkable progress in science and technology, combating infectious diseases still poses a major challenge. Therefore, scientists are continually seeking new ways to tackle these diseases. Traditional drug development and conventional dosage formulations are sometimes inadequate in treating certain infectious diseases and thus require a more innovative approach. In recent years, nanotechnology has shown great promise in the field of medicine. By utilizing the unique properties of nanomaterials, researchers are developing novel drug delivery systems that have the potential to enhance the effectiveness of existing drugs and overcome the limitations of conventional treatment methods. Nanotechnology-based drug delivery systems have several advantages, including targeted delivery to the site of infection, increased bioavailability, and reduced toxicity. This book aims to provide readers with an in-depth understanding of the potential of nanomedicine in the prevention and treatment of infectious diseases. The present book offers a comprehensive and up-to-date account of the cutting-­ edge developments in nanomedicine that hold immense promise for the prevention and treatment of infectious diseases. With a broad range of topics covered, the book delves into diverse formulation strategies for microbial, fungal, parasitic, and viral infections and explores the production of nano-scale vaccines, which have significant advantages over traditional vaccines. It also discusses various feasible treatment modalities for parasitic infections like malaria and trypanosomiasis, fungal infections such as candidiasis, and viral diseases including Hepatitis B, HIV, and the v

vi

Preface

ongoing COVID-19 pandemic. In addition, the book sheds light on the role of nano-­ adjuvants in vaccine preparation and the use of peptide antibiotics and pulmonary delivery of antibiotics, which provide a new frontier for drug delivery in the fight against infectious diseases. Furthermore, the book explores the critical role of nanomedicine in addressing the challenges of veterinary parasitic infections. With the emergence of nanotechnology, novel strategies have been developed for the diagnosis, treatment, and prevention of parasitic infections in animals. These approaches have the potential to significantly improve the health and well-being of animals, particularly in impoverished communities where veterinary care is limited. The book also highlights the need for further research and development in this field to enhance the efficacy of nanomedicine for combating veterinary parasitic infections. The multidisciplinary author panel of this book includes experts from diverse fields, such as anatomy, physiology, pharmacology, drug and dosage form development, and regulatory and commercialization expertise, making it a valuable resource for anyone interested in the latest developments in nanomedicine for the prevention and treatment of infectious diseases. The authors offer unique perspectives and insights into the barriers and novel approaches for delivering anti-infectious agents with improved therapeutic benefits of the parent compounds, and each chapter provides an in-depth analysis of the latest research in the field. With its comprehensive coverage and expert contributions, this book is an essential reference for researchers, clinicians, and policymakers interested in advancing the field of nanomedicine. We believe that this book will prove to be an indispensable resource for scholars, students, and professionals in the field of infectious diseases. Our objective is to inspire innovative approaches and ideas for the prevention and treatment of infectious diseases by presenting a comprehensive overview of the latest advances in nanomedicine. Ultimately, we hope that these advancements will contribute to better outcomes for patients globally. Matunga, Mumbai, India Tuscon, AZ, USA Jhunjhunu, Rajasthan, India

Vandana B. Patravale Abhijit A. Date Anil B. Jindal

Acknowledgements

We extend our heartfelt gratitude to all the individuals who have played a critical role in the development and success of this book, Nanomedicine for the Prevention and Treatment of Infectious Diseases. We are deeply grateful to the distinguished experts from academia and industry who have generously shared their knowledge, insights, and expertise to bring this book to fruition. Their invaluable contributions have elevated the quality and impact of this work, and we sincerely appreciate their time and effort. We also want to express our sincere thanks to the AAPS Advances in Pharmaceutical Sciences series editor and the editorial board members for their invaluable feedback during the proposal review process. We are equally grateful to the publishing editor, Merry Stuber, and the project coordinator, Vishnu Prakash, for their unwavering support throughout the manuscript submission and publication process. Their dedication and guidance have been instrumental in shaping this book and making it successful. Our student team deserves special recognition for their unwavering commitment and hard work. Their dedication to formatting the manuscript and ensuring it meets the publisher’s requirements has been invaluable. We are immensely thankful for their contributions and support. Finally, we would like to extend our heartfelt thanks to all those who have supported us along this journey, including our mentors, family, friends, and colleagues. Your encouragement and assistance have been essential to the success of this book, and we deeply appreciate your contributions.

vii

Contents

 Nanocarriers for Delivery of Peptide Antibiotics������������������������������������������    1 Bharathi Karunakaran, Jyotsna Vitore, Amit Sharma, Dhwani Rana, and Derajram Benival  Nanomedicines for the Pulmonary Delivery of Antibiotics��������������������������   35 Arnab Ghosh and Rohit Srivastava Inhalable Nanomedicines for the Treatment of Pulmonary Aspergillosis������������������������������������������������������������������������������������������������������   77 Basanth Babu Eedara, David Encinas-Basurto, Bhagyashree Manivannan, Don Hayes Jr, and Heidi M. Mansour  Nanomedicines for the Treatment of Systemic Candidiasis ������������������������   95 Dhwani Rana, Sagar Salave, Garima Rawat, and Derajram Benival  Nanomedicine for the Treatment of Vaginal Candidiasis����������������������������  125 Richa Vartak, Suvidha Menon, Manali Patki, Xiuyi Liang, Blasé Billack, and Ketan Patel  Nanomedicines for the Treatment of Veterinary Parasitic Infections ��������  149 Dhanashree H. Surve, Atharva Bhide, Anil B. Jindal, and Padma V. Devarajan Role of Nanotechnology Against Malaria: Current Perspectives and Strategies ��������������������������������������������������������������������������������������������������  197 Satyam Gupta, Chukwuebuka E. Umeyor, and Vandana B. Patravale  Nanomedicines for the Treatment of Trypanosomiasis��������������������������������  239 Kedar S. Prayag and Anil B. Jindal  Nanomedicines to Improve Oral Delivery of Antiretroviral Drugs������������  265 Oly Katari and Sanyog Jain Nano-Adjuvants ����������������������������������������������������������������������������������������������  297 Bishal Misra, Krystal A. Hughes, and Sharan Bobbala ix

x

Contents

Nanoscale Vaccines for Influenza ������������������������������������������������������������������  331 Shashank Bhangde, Rushit N. Lodaya, and Mansoor M. Amiji  Nanoscale Vaccines for the Prevention of Hepatitis B Virus Infection��������  349 Poornima Ramburrun, Mershen Govender, and Yahya E. Choonara  Nanoscale Vaccines for the Prevention of COVID-19 ����������������������������������  367 Mir Javid Iqbal, Tooba Hamdani, Husain Z. Attarwala, and Mansoor M. Amiji Index������������������������������������������������������������������������������������������������������������������  403

Contributors

Mansoor M. Amiji  Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA Department of Chemical Engineering, College of Engineering, Northeastern University, Boston, MA, USA Husain Z. Attarwala  Aera Therapeutics, Cambridge, MA, USA Derajram  Benival  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Shashank Bhangde  Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA Atharva  Bhide  Department of Pharmacy, Birla Institute of Technology and Science Pilani, Jhunjhunu, Rajasthan, India Blasé  Billack  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA Sharan  Bobbala  Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA Yahya  E.  Choonara  Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Padma  V.  Devarajan  Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Mumbai, India

xi

xii

Contributors

Basanth  Babu  Eedara  Center for Translational Science, Florida International University, Port St. Lucie, FL, USA David  Encinas-Basurto  Department of Physics, Mathematics and Engineering, University of Sonora, Navojoa, Sonora, México Arnab Ghosh  NanoBios Lab, Indian Institute of Technology, Bombay, India Mershen  Govender  Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Satyam Gupta  Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology (Elite status), Deemed University, Matunga, Mumbai, India Tooba Hamdani  Wolfson Institute of Population Health, Queen Mary University of London, London, UK Don  Hayes Jr  Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA Division of Pulmonary, Critical Care, and Sleep Medicine, University of Cincinnati Medical Center, Cincinnati, OH, USA Department of Pediatrics and Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA Krystal A. Hughes  Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA Mir Javid Iqbal  School of Pharmacy and Pharmaceutical Sciences, Northeastern University, Boston, MA, USA Sanyog  Jain  Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar, Punjab, India Anil B. Jindal  Department of Pharmacy, Birla Institute of Technology and Science Pilani, Jhunjhunu, Rajasthan, India Bharathi  Karunakaran  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Oly  Katari  Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar, Punjab, India Xiuyi  Liang  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA

Contributors

xiii

Rushit  N.  Lodaya  GSK Vaccines, Rockville Center for Vaccines Research, Rockville, MD, USA Bhagyashree Manivannan  Center for Translational Science, Florida International University, Port St. Lucie, FL, USA Heidi  M.  Mansour  Center for Translational Science, Florida International University, Port St. Lucie, FL, USA Suvidha Menon  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA Bishal Misra  Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA Ketan  Patel  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA Manali  Patki  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA Vandana B. Patravale  Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology (Elite status), Deemed University, Matunga, Mumbai, India Kedar  S.  Prayag  Department of Pharmacy, Birla Institute of Technology and Science Pilani, Jhunjhunu, Rajasthan, India Poornima  Ramburrun  Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Dhwani Rana  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Garima Rawat  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Sagar Salave  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Amit Sharma  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India Rohit Srivastava  NanoBios Lab, Indian Institute of Technology, Bombay, India Dhanashree  H.  Surve  Department of Chemical Engineering, University of Massachusetts, Amherst, MA, USA

xiv

Contributors

Chukwuebuka E. Umeyor  Nanomedicines and Drug Delivery Research Group, Department of Pharmaceutics and Pharmaceutical Technology, Institute of Chemical Technology, Mumbai, India Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria Richa  Vartak  College of Pharmacy and Health Sciences, St. John’s University, Jamaica, NY, USA Jyotsna Vitore  Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER–A), Gandhinagar, Gujarat, India

About the Editors

Vandana B. Patravale  is currently a Professor of Pharmaceutics at the Institute of Chemical Technology, Mumbai, India. She has around 30 years of teaching and research experience. She has over 200 refereed publications (h index: 45, i10 index: 109), 15 granted patents, 22 patents in the pipeline, and 2 trademark registries. She has published 2 books and 30 book chapters with international publishers. Dr. Patravale has been active in teaching, research, and service throughout her career and has been bestowed with several national and international awards. Her research is focused on the development of nanocarriers with major emphasis on infectious diseases, cancer, and neurodegenerative disorders; medical device development; nanodiagnostics; and nanovaccines. She is the Vice president-CRS Indian chapter, editorial board member DDTR, editor CRS IC, and APTI women forum newsletters. She is actively collaborating with researchers as well as industries within India and abroad and has transferred about 20 technologies to the industry including drug-eluting stents being marketed in more than 60 countries. Abhijit  A.  Date  is currently an Assistant Professor at the Department of Pharmacology and Toxicology, R.  K. Coit College of Pharmacy, University of Arizona. He is a pharmaceutical scientist by training with vast experience in the development and pre-clinical evaluation of conventional and novel drug delivery systems including nanomedicines. He is listed as an inventor on four US/PCT patents or patent applications. He has 69 peer-reviewed publications (h index: 31) and 5 book chapters to his credit, and his research work have been published in the renowned drug delivery/translational journals like Nature Biomedical Engineering, Clinical Cancer Research, Biomaterials, Journal of Controlled Release, Bioengineering and Translational Medicine, International Journal of Pharmaceutics, ACS Infectious Diseases, and Molecular Pharmaceutics. He received the Johns Hopkins Center for Nanomedicine research excellence award in 2016. He has been a recipient of the DKICP Student Choice Award for Teaching in Pharmaceutical Sciences in 2018, 2019, 2020, and 2021  during his tenure at the University of Hawaii Hilo. He serves as the Associate Editor for Frontiers in Nanotechnology, and

xv

xvi

About the Editors

as a reviewer for more than 30 drug delivery journals. Dr. Date’s current research work is focused on drug repurposing and reformulation for the treatment of cancer and infectious diseases with limited treatment options. Anil  B.  Jindal  is an Associate Professor at the Department of Pharmacy, Birla Institute of Technology and Science, Pilani Campus. His research is focused on developing innovative drug delivery systems to treat infectious diseases in both humans and animals. Dr. Jindal holds a PhD from the Institute of Chemical Technology Mumbai and worked with leading pharmaceutical companies such as Pfizer and IPCA Laboratories before joining BITS Pilani. He is the author of numerous publications and book chapters and the inventor of three patent applications in nano-drug delivery systems. He is also an editor of the book Pharmaceutical Process Engineering and Scale-Up Principles, published by Springer as a part of AAPS Introduction in the Pharmaceutical Sciences Series. Dr. Jindal’s contributions to the field of drug delivery earned him several prestigious academic awards, including the Prof. M.L. Khorona Memorial Award in 2010, the Eudragit Award in 2018, and the Early Career Research Award in 2019, presented by SERB, Government of India, for his significant contribution to research. Dr. Jindal’s interview was recently featured in Voices Editorial of Molecular Pharmaceutics, demonstrating his recognition as a thought leader in his field. Additionally, he has been appointed as a managing theme editor for Advanced Drug Delivery Reviews, a highly respected journal with an impact factor of 17.87.

Nanocarriers for Delivery of Peptide Antibiotics Bharathi Karunakaran, Jyotsna Vitore, Amit Sharma, Dhwani Rana, and Derajram Benival

Abstract  Bacterial infections pose a major threat to public health due to continuous bacterial growth and their resistance to conventional antibiotics. The recent increase in cases of antibiotic resistance and the failure of conventional antibiotics have created an urgent need to overcome this barrier. This fact urged the discovery of new therapeutic alternatives for the eradication of bacterial infections. Antibacterial peptides (ABPs) have emerged as a functional key tool in the management of bacterial infections. ABPs possess a wide spectrum of antimicrobial activity and are vital components of the innate immune system, which can pose a minimal risk of developing resistance. Although ABP has a broad range of therapeutic applications, its utility is limited due to concerns such as stability, manufacturing process, and associated toxicity. Nanocarriers have the potential to overcome all these shortcomings associated with different ABPs, and therefore, ABP-based nanocarriers present a novel approach for efficient treatment against bacterial infections. In this chapter, the importance of different nanocarriers in ABP delivery is discussed. Further, the various applications of nanocarriers and limitations of nanocarrier-­ based peptide antibiotics are also addressed. Keywords  Antimicrobial resistance · Multidrug resistance · Antibacterial peptides · Drug delivery · Nanocarriers

B. Karunakaran · J. Vitore · A. Sharma · D. Rana · D. Benival (*) Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research–Ahmedabad (NIPER-A), Gandhinagar, India e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 V. B. Patravale et al. (eds.), Nanomedicines for the Prevention and Treatment of Infectious Diseases, AAPS Advances in the Pharmaceutical Sciences Series 56, https://doi.org/10.1007/978-3-031-39020-3_1

1

2

Abbreviations ABPs Antibacterial peptides ABSSSI Acute bacterial skin and skin structure infections ADA Adamantane AMF Alternating magnetic field AMPs Antimicrobial peptides AMR Antimicrobial resistance CAMP Cationic antimicrobial peptide CFDA China Food and Drug Administration CS Chitosan cSSSI Complicated skin and skin structure infections DSC Differential Scanning Calorimetry EDTA Ethylenediamine tetraaceticacid FAL Fatty acid lipids GBR Guided bone regeneration GIT Gastrointestinal tract GMO Glyceryl monooleate HD6 Human α-defensin 6 LCS Liquid Crystalline System MDR Multidrug Resistance MIC Minimum inhibitory concentration MRSA Methicillin-­resistant Staphylococcus aureus MSN Mesoporous silica nanoparticles MSNLP Mesoporous silica nanoparticles with large pores nHAP Hydroxyapatite nanoparticles NLC Nanostructured lipid carriers PCL Polycaprolactone PDI Polydispersity Index PEG Polyethylene glycol PEICD Polyethyleneimine PEO Polyethylene oxide PHYT Phytantriol PLGA Polylactic-co-­glycolic acid SAXS Small angle X-ray scattering SLN Solid Lipid Nanoparticle SPPS Solid Phase Peptide Synthesis SWOT Strengths, weaknesses, opportunities, and threats TEM Transmission electron microscopy USFDA United States Food and Drug Administrarion WAXD Wide angle X-ray diffraction WHO World Health Organization WPI Whey protein isolate β-CD β-cyclodextrin

B. Karunakaran et al.

Nanocarriers for Delivery of Peptide Antibiotics

3

1 Introduction Antibiotics are substances that inhibit the growth of bacteria and are used in the prevention and treatment of bacterial infections. They work by killing bacteria or restricting their reproduction and may be synthesised chemically or by naturally occurring or engineered organisms [1]. Antibiotic resistance arises when bacteria adapt to the usage of these medications. The long-term and widespread use of conventional antibiotics has provoked the development of multidrug resistance in ­bacterial species. Antimicrobial resistance (AMR) is a growing worldwide health issue that can make it difficult to treat bacterial infections in some situations [2]. The increased prevalence of drug-resistant bacteria is responsible for rising mortality and morbidity rates. The World Health Organization (WHO) named AMR as one of the top ten global public health threats facing humanity, with an estimated 10 million deaths per year by 2050 [3]. The majority of multidrug resistance (MDR) infections require long-term antibiotic treatment and are accompanied by significant healthcare costs [4]. Conventional antibiotics have limited activity against resistant bacterial species, and only a few antibiotics are available to combat the MDR bacteria. Several compounds are being researched for the development of novel antibacterial treatments to address this unmet need. Alternative medications based on antimicrobial peptides (AMPs), which play a crucial role in innate immunity, are in the research pipeline. AMPs protect both vertebrates and invertebrates from a wide range of microorganisms as part of the innate immune system. AMPs are one of the most promising alternatives to conventional antibiotics since they have the potential to treat bacterial infections, particularly those caused by MDR organisms [2]. Amongst them, antibacterial peptides (ABPs) are target-specific and potent candidates for overcoming bacterial resistance. Although ABPs have many benefits over conventional antibiotics, their clinical application is limited due to issues like poor gastrointestinal tract (GIT) stability, aggregation, and changes in structural configuration. Advances made in the field of nanotechnology can now be used to deliver peptide-based antibiotics. Many investigations reported in the literature have shown promising results with advanced nanocarriers for ABP delivery. It has been demonstrated that improvements in the antibacterial activity of ABP can be attributed to a variety of mechanisms, including prominent antibiotic internalisation, optimising pharmacokinetics, interfering with bacterial metabolism, biofilm penetration, and modulating biofilm microenvironments [5]. Nanotechnology can enable the design, development, characterisation, and application of various nanocarrier-based systems, which are below 1000 nanometre scale [6]. Nanocarriers have the ability to circumvent the barrier ABPs encounter due to their instability and toxicity and hence can contribute to the development of novel therapeutics for efficient management of various bacterial infections [7]. This chapter discusses characteristics of antibacterial peptides and the role of nanocarriers in delivering the antibacterial peptides.

4

B. Karunakaran et al.

2 ABPs: An Imperative Subset of AMPs AMPs are a class of small polypeptide molecules, typically made up of around 12–50 amino acids, found in all classes of living organisms, from prokaryotes to humans [2]. AMPs, which are also called as host defence peptides and produced as secondary metabolites plays a significant role in the innate immune systems of several organisms. The AMPs are evolutionary conserved in the genome of all life forms [8]. They exhibit a wide range of inhibitory effects against bacteria, fungi, parasites, and viruses. AMPs are multifunctional molecules that have a central role in infection and inflammation, as the level of native AMPs is upregulated during injury or bacterial infection in higher organisms [9]. Most AMPs have the potential to directly destroy microbial infections, whereas others operate indirectly by altering the host defence mechanisms. Due to the widespread emergence of antimicrobial resistance all around the world, attempts to put AMPs into clinical usage are accelerating [2]. Statistically, ABPs account for the largest proportion, approximately 60% of the AMPs. AMPs having antibiotic properties (ABPs) demonstrated inhibitory action against variety of bacterial infections including Vancomycin-resistant Enterococci, Acinetobacter baumannii, and Methicillin-resistant Staphylococcus aureus (MRSA) [10]. Numerous ABPs have been discovered in the past decade; however, due to associated limitations, only few are introduced into the clinical practice and are listed in Table 1. Antibacterial peptides fall into two types based on their synthesis, including non-ribosomally synthesised peptides, such as polymyxins, bacitracins, gramicidins, glycopeptides, and ribosomally synthesised peptides. The former is often modified and predominantly produced by bacteria, while the latter is produced by all species of life (including bacteria) as natural host defence molecules [11].

2.1 Principal Characteristics and Biological Role of ABPs In addition to interacting directly with bacterial membranes, a subset of ABPs also possesses inhibitory capabilities to target bacterial biopolymers. Yet others, such as cathelicidins or defensins, exhibit upregulation of host’s immune system [19]. ABPs can also have a membrane permeabilisation effect and/or affect specific intracellular activities. The activity and specificity of peptide antibiotics are governed by a variety of factors including their amino acid composition, size, secondary structure, charge, hydrophobicity, conformation, or amphiphilic character [2]. One of the mechanistic pathways representing the antibiotic characteristic of ABPs is the electrostatic interaction with the anionic phospholipid membranes of bacteria. This interaction followed by formation of transient pores or channels leads to membrane disruption called as “barrel stave” mechanism. Alternatively, as per the “carpet” model, ABPs cooperatively destroy the membrane barrier without channel formation. On the other hand, ABPs bind to the outer leaflet of model membranes and flip

Origin Bacillus subtilis

Semisynthetic derivative of vancomycin

Gram-­ positive bacteria Gram-­ positive bacteria

Teicoplanin Actinoplanes teichomyceticus

Telavancin

Gram-­ positive bacteria

Vancomycin Streptomyces orientalis

Oritavancin Kibdelosporangium orienticin

Dalbavancin Non-omuraea

Daptomycin Streptomyces roseosporus

Peptide Bacitracin

Effective against organism Gram-­ positive bacteria Gram-­ positive bacteria Gram-­ positive bacteria Gram-­ positive bacteria

Table 1  Marketed antibacterial peptides (ABPs)

Glycopeptide

Inhibit bacterial cell Complicated skin wall synthesis and skin structure infections (cSSSI)

Mechanism of antibacterial action Inhibits the bacterial cell wall synthesis Membrane lysis

Indication Topical infection/ superficial ocular infections Lipopeptide Complicated skin and skin structure infections (cSSSI) Lipoglycopeptide Inhibits the Acute bacterial skin bacterial cell wall and skin structure synthesis infections (ABSSSI) Lipoglycopeptide Inhibit bacterial cell Acute bacterial skin wall synthesis and and skin structure inhibition of the infections (ABSSSI) transpeptidation Glycopeptide Inhibition of Serious or severe bacterial cell wall infections caused by susceptible strains of methicillin-­ resistant (β-lactam resistant) staphylococci Glycopeptide Inhibit bacterial cell Skin and soft tissue wall synthesis infection

Class Cyclic peptide

Intravenous infusion

Intravenous

250 and 750 mg/vial

400 mg/vial

500 mg/vial

Intravenous

Intravenous & intramuscular

Intravenous

1200 mg/vial Intravenous

500 mg/vial

500 mg/vial

Route of Dose administration 50,000 units/ Topical vial Ophthalmic

[18]

[17]

[16]

[15]

[14]

[13]

References [12]

Nanocarriers for Delivery of Peptide Antibiotics 5

6

B. Karunakaran et al.

Fig. 1  Mechanism of action of ABPs, their limitations, and advantages of nanocarriers in delivering ABPs

inward, carrying lipids along the way and creating brief disruptions in permeability [19, 20]. Apart from the membrane activities, the mode of action of ABPs is via interaction with the cellular targets. Stimulation of autolytic enzymes, binding and inhibition of cellular nucleic acids [20]. The mechanism of action of ABPs, their limitations, and advantages of nanocarriers in delivering ABPs are shown schematically in Fig. 1. The antibacterial activity of ABPs differs from that of conventional antibiotics, and they are ubiquitous [19]. Various physicochemical properties such as net charge, as well as differences in mode of action, surface modification distinguishes them from conventional antibiotics. ABPs are independent of bacterial innate metabolic regulation, whereas conventional antibiotics are dependent upon the metabolic machinery. Because ABP has a high potential for activity against microbial flora, microorganisms are less resistant to ABPs than conventional antibiotics [21]. Despite their broad antibacterial activity, some ABPs have undesirable characteristics for clinical usage. They portray certain toxicity to eukaryotic cells, which can lead to haemolysis, nephrotoxicity, and neurotoxicity; susceptibility to proteolysis by bacterial proteases; and their unclear pharmacokinetic profile [22].

3 Role of Nanotechnology in Delivering ABPs Advances in nanobiotechnology have enabled various nanostructures to function as an effective strategy for minimising the undesirable properties of natural and synthetic ABPs. ABPs in nanostructures have been shown to exert lower cytotoxicity, less degradation, and higher efficiency at the target site [22]. The loading of ABPs

Nanocarriers for Delivery of Peptide Antibiotics

7

into the nanocarriers could circumvent biological barriers in organisms such as the acidic pH and enzymes present in the gastrointestinal lumen, mucosa, as well as epithelial layers in the intestine. Nanocarriers employ two main approaches for drug targeting: passive and active targeting. Conventional passive drug targeting systems do not possess advanced surface modification to guide the nanocarrier. This can be controlled by the size and shape of the nanocarrier [23]. In addition, surface hydrophobicity and charge of nanocarriers also influence their in vivo fate. Surface hydrophobicity of nanocarriers can be an important attribute for drug targeting by interaction with the phospholipid content of bacterial membranes. On the other hand, nanocarriers having hydrophilic surfaces generally exhibit minimal interaction with the opsonins, and thus, they possess longer blood circulation than the nanocarriers having hydrophobic surfaces [24]. Surface charge of nanocarriers triggers the interactions with biomolecules like proteins or with various components of the tissue, affecting cellular biodistribution and uptake. Macrophages are known as innate defence cells, which drain out to the injury site and mediate the inflammatory process. Some findings have revealed that characteristics like particle size and shape may have an influence on internalisation efficiency by macrophages [25]. Active targeting of nanocarriers involves surface modification using ligands and other functionalities that can interact with cells and enhance drug transport at specific target sites. Thus, the enhancement of ABP stability, controlled release, and targetability makes nanocarriers excellent for enhancing activity of ABPs [26]. Several types of nanocarriers are explored for the delivery of ABPs and are illustrated in Fig. 2, while Table 2 summarises research applications of nanocarriers for enhancing the activity of ABPs.

3.1 Inorganic Nanocarriers Mesoporous Silica Based Nanocarriers One of the most widely used inorganic vehicles for drug delivery is mesoporous silica nanoparticles (MSN). These MSN offers an interesting strategy for the ­efficient delivery of cargo ranging from small molecules (drugs) to large molecules (proteins). MSN has also been used to load and deliver ABPs. Tenland et  al. employed MSN to incorporate an ABP named NZX into primary macrophages to inhibit intracellular mycobacteria. The MSNs were fabricated with a mean diameter of 200 nm to allow rapid cellular uptake by alveolar macrophages. In a TB murine model, NZX with MSNs dramatically reduced bacterial load to levels comparable to rifampicin treatment. The peptide-loaded MSN showed higher intracellular antimycobacterial efficacy compared to free ABP. The authors reported that the increased activity was linked to macrophage uptake and preserving the antibacterial activity of drug [27]. In another study, Haffner et  al. explored the influence of nanoparticle topography on lipid membrane interactions of MSN. They compared both MSN as well as virus-like MSN with a “spiky” outer surface. These findings

8

B. Karunakaran et al.

Fig. 2  Nanocarriers for delivery of ABPs

highlighted the possibility of designing virus-like MSN as AMP delivery vehicles. Additionally, they have demonstrated the virus-like nanoparticles caused membrane-­ disruptive effects and promotes incorporation of LL-37 throughout bacteria-­ mimicking bilayers model formed by palmitoyl oleoyl phosphatidylcholine/ palmitoyl oleoyl phosphatidylglycerol [28]. Yu Qilin and co-workers designed multi-stimuli-responsive nanomaterials to co-deliver high molecular weight ABP with small antibiotic molecule for synergistic eradication of pathogenic biofilms. For this codelivery of drugs, they have prepared a magnetic core containing MSN (MagNP@MSNA) capped by cucurbit [6] uril (CB [6]) with different modifications such as MSN with large pores (MSNLP), end-capped by β-cyclodextrin (β-CD), polyethyleneimine (PEICD) and adamantane (ADA). By utilising interactions of β-CD and ADA, they prepared co-assemblies of host (H, MSNLP@PEICD) and guest (G, MagNP@MSNA-CB [6]). Morphological assessment revealed that the obtained MSNLPs had particle sizes of 90~110  nm and pore sizes of 7~10  nm. Compact packing by a thin bright layer of PEICD on MSNLPs was also observed from transmission electron microscopy (TEM) analysis. The release of the large molecular weight peptide (Melittin) and small molecular weight antibiotic (Ofloxacin) occurs when there is an AMF (alternating magnetic field) heating and by the stimuli-responsive pathogen cell. The results of this study revealed the potential of the MSN as a nanocarrier system for co-delivering multidrugs with different physicochemical properties in order to improve antibacterial efficacy [29].

Nanocarriers for Delivery of Peptide Antibiotics

9

Table 2  Reported nanocarriers to enhance efficacy of ABPs with their research outcomes Nanocarrier MSN

ABP used NZX

MSN

Melittin

Microorganism to target Type of study M. tuberculosis In vivo mouse model of tuberculosis

P. aeruginosa

S. epidermidis Mesoporous ABP (RRP9W4N) titania nanoparticles

Cubosomes

β-defensin-3 peptide fragment (D1-23)

S. mutans

Cubosomes

Gramicidin A, Melittin, Alamethicin

No antimicrobial study performed

Research outcomes As compared to untreated control, an ≈ 88% reduction in colony-forming units in the lungs of mice was observed In vivo biofilm Combination treatment with implantation model in mouse ofloxacin co-delivered gives ≈ 100% bacterial killing efficiency The use of In vivo study osseointegration ABP-loaded mesoporous and bone healing in rabbit titania could help to reduce tibia the risk of implant-related infections In vitro study D1-23 loaded cubosomes reduced the bacterial biomass by tenfold after 24 hours of treatment, compared to D1-23 alone In vitro study Encapsulation of ABP in cubosomes promoted the drug release and prevented the peptides from degradation

References [27]

[29]

[31]

[44]

[45]

(continued)

B. Karunakaran et al.

10 Table 2 (continued) Microorganism to target S. aureus, Bacilus cereus, Escherichia coli, and Pseudomonas aeruginosa

Nanocarrier Cubosomes

ABP used Gramicidin A, Alamethicin, Melittin, Indolicidin, Pexiganan, Cecropin A

Cubosomes

DPK-060

S. aureus

SLN

Polymyxin

P. aeruginosa

SLN

LL37

S. aureus and E. coli

Research outcomes Concluded two things. Firstly, inhibition of bacterial growth was due to the significant release of ABP from cubosomes to the surrounding media and, secondly, low, or incomplete uptake of cubosomes into bacteria was observed Pig skin ex vivo No additional wound infection benefit was observed when model DPK-060 was incorporated into cubosomes In vitro study SLN having >90% encapsulation efficiency and low mean particle size and demonstrated effectiveness against P. aeruginosa-­ resistant strains In vitro study LL-37, Serpin A1 (A1) (elastase inhibitor) loaded in SLN promotes the wound healing activity and increases the antibacterial activity against S. aureus and E. coli Type of study In vitro study

References [46]

[68]

[47]

[48]

(continued)

Nanocarriers for Delivery of Peptide Antibiotics

11

Table 2 (continued) Microorganism to target S. aureus, S. epidermidis, and E. coli

Nanocarrier NLC

ABP used Nisin Z

NLC

LL37

E. coli

Chitosan OH30 nanoparticles

E. coli

Research outcomes Nisin Z could be useful as an adjuvant in antimicrobial chemotherapy while also helping to fight antibiotic resistance. NLCs have the potential to boost nisin Z’s antibacterial efficacy against gram-positive bacteria that cause skin infections In vitro, in vivo Administration of 6 μg of LL37 full-thickness wound model in topically improved wound db/dbmice healing compared to the administration of the free LL37 In vitro, in vivo When compared wound healing to the native OH30 assay encapsulation with carboxymethyl chitosan, it resulted in better keratinocyte migration and accelerated wound healing Type of study In vitro study

References [49]

[50]

[36]

(continued)

12

B. Karunakaran et al.

Table 2 (continued) Nanocarrier ABP used Chitosan Pep-H nanoparticles

Microorganism to target Type of study M. tuberculosis In vitro study

Chitosan Ultrashort nanoparticles ABP (RBRBR)

S. aureus

In vitro study

PLGA GIBIM-­ nanoparticles P5S9K (G17), GAM019 (G19)

E. coli, MRSA

In vitro study

Research outcomes A 5–10 times lower concentration of nanoparticles loaded with antibacterial peptides is sufficient to achieve a >90% significant reduction in colony forming unit analysis as compared to free antibacterial peptide When compared to bare nanoparticles, there was a 3-log reduction in bacterial colonies, and a 5 log drop when compared to control bacteria Reduction in MIC 50 1.5 to 0.2 (G17 nanoparticles) and 0.7 (G19 nanoparticles) μM against MRSA, and from 12.5 to 3.13 μM for E. coli and improvement in antibacterial activity observed

References [37]

[69]

[34]

Mesoporous Titania Based Nanocarriers Mesoporous titania is a biocompatible, cost-effective, chemically stable, and innocuous material with large porosity and a high surface area, which makes it a suitable carrier for the efficient delivery of ABP. It can be used to prevent bacterial infection on medical devices like dental and orthopaedic implants [30]. Pihl et al. prepared

Nanocarriers for Delivery of Peptide Antibiotics

13

mesoporous titania-covered implants using an ABP, RRP9W4N and investigated how it influenced osseointegration at the implant healing site. For this, ABP was loaded into mesoporous titania, which was further coated on titanium implants. Electron microscopy was used to examine the mesoporous titania. The titania was clearly visible in TEM as a continuous mesoporous network with pore diameters of around 6 nm. The authors concluded from this experiment that ABP-loaded mesoporous titania could be a suitable choice for reducing implant-related infections [31].

3.2 Polymeric Nanocarriers Natural polymers such as chitosan and collagen, as well as synthetic polymers like polylactic-co-glycolic acid (PLGA) and polycaprolactone (PCL) are non-toxic, non-immunogenic, and biodegradable in nature. Nanocarriers made up of these biodegradable polymers can be used to achieve various functionalities for ABPs including controlled release, stability, and toxicity reduction. Crystallinity, hydrophobicity, and molecular weight are some of the important physicochemical properties known to affect drug release from polymeric nanocarriers [32]. PLGA Based Nanocarriers PLGA is one of the most widely used biodegradable polymer in development of controlled-release drug delivery. PLGA polymer can be used to load antibiotics, proteins/peptides, and nucleic acids and to target it to various phases/signalling cycles of wound healing. The ester linkages in PLGA are broken down during hydrolysis, resulting in the generation of both lactic and glycolic acids. Interestingly, the antibacterial selectivity of ABP is influenced by environmental pH and is dependent on its net charge. At low pH, ABP effectively kills gram-negative bacteria such as E. coli and P. aeruginosa, but its sterilising effectiveness against gram-positive bacteria such as staphylococci is compromised [33]. Gomez-sequeda et  al. prepared GIBIM-P5S9K (G17) and GAM019 (G19) peptide-­loaded PLGA nanoparticles and evaluated their antibacterial activity against E. coli and S. aureus. The results from this study suggested that encapsulation of these peptides into the PLGA nanoparticles improved their antimicrobial activity and decreased their MIC50 concentration by 2–4 folds. Further, in comparison to G17 peptide, G19 peptide demonstrated strong antibacterial activity against MRSA.  In conclusion, these bacteriostatic peptides loaded nanoparticles demonstrated potential application in treating bacterial E. coli O157:H7 and MRSA infections [34].

14

B. Karunakaran et al.

Chitosan-Based Nanocarriers Chitosan (CS) is a polycationic biocompatible polysaccharide-based polymer. Various studies have demonstrated antimicrobial activity of chitosan against yeast, fungi, and gram-negative as well as gram-positive bacteria [35]. Sun et al. utilised the ion gelation technique to encapsulate the OH-CATH30 (OH30) peptide in carboxymethyl chitosan nanoparticles and tested it for wound healing activity owing to the potent antibacterial activity of the peptide. The researchers observed sustained OH30 release from the nanoparticles as well as enhanced antibacterial action against E. coli. Compared to OH30 alone, encapsulation of OH30 in carboxymethyl chitosan nanoparticles, led to faster wound healing in full-thickness wound animal model. By suppressing immune responses in the early stages of wound healing, the released OH30 promotes scarless healing, and it also plays a crucial role in influencing collagen I and III in the later stages [36]. In a recent study, Sharma et al. performed an in silico antimycobacterial activity study for a short antimicrobial motif (Pep-H). They compared the antimycobacterial activity of Pep-H in free form and by formulating a nanoparticle-based delivery system. It was concluded from this study that 5–10 times lower concentrations of Pep-H in the form of nanoparticles are needed to achieve >90% reduction in colony forming unit as compared to free antimicrobial peptide [37]. Polymeric Nanofibres Polymeric nanofibres have been investigated to be an interesting strategy for drug delivery. It has promising characteristics such as large surface area to volume ratio, high porosity of the nanofibre mesh, and tunable release profile such as sustained release. In one such study, antimicrobial nanofibre-based wound dressing was prepared by electrospinning nisin into the blend of poly (ethylene oxide) and poly(d,l-­ lactide) (50:50) nanofibres. During in vitro testing, sustained release (at least 4 days) of nisin from the nanofibre wound dressings was observed, which was evident by consecutive transfers onto plates seeded with strains of MRSA. The developed antimicrobial dressing also caused significant reduction in S. aureus Xen 36 bioluminescence in an in vivo experiment and viable cell numbers in a murine excisional skin infection model. In addition, stimulated wound closure of excisional wounds were observed with the developed nanofibre-based dressing. These results suggest that nisin loaded nanofibre-based wound dressings have the potential to treat S. aureus skin infections and to promote wound healing of excisional wounds [38]. In the treatment of bone defects caused by peri-implantitis, periodontal disease, and many other conditions, the Guided bone regeneration (GBR) technique is widely used. However, the membranes of GBR which are commonly used in clinical treatments, currently do not have antibacterial activity. To prepare one such membrane, which is supposed to have osteogenic and antibacterial activities, He et  al. used sequential layer-by-layer electrospinning and electrospraying technique to prepare a gelatin and chitosan-based composite GBR membrane containing hydroxyapatite

Nanocarriers for Delivery of Peptide Antibiotics

15

nanoparticles (nHAp) and antimicrobial peptide (Pac-525)-loaded PLGA microspheres (AMP@PLGA-MS). In vitro cell culture study indicated that the gelatin and chitosan composite membrane containing nHAp could promote osteogenic differentiation of rat bone marrow mesenchymal stem cells. In addition, antibacterial experiments indicating antibacterial activity up to 1 month against tested two kinds of bacteria, S. aureus and E. coli suggesting the potential of developed membrane in bone generation-related applications as well as inhibiting bacterial infection after implantation of the same [39]. Similarly, Julieth Tatiana Román et  al. developed pullulan nanofibres containing the antimicrobial palindromic peptide LfcinB (21-25)Pal by electrospinning, and it was found effective against E. coli strain. The study outcomes also revealed that the electrospinning process does not compromise the peptide integrity [40]. In a different study, Nafise Amara et  al. developed teicoplanin-­loaded chitosan-polyethylene oxide (PEO) based nanofibres for localised antibiotic delivery. A sustained release of teicoplanin up to 12  days was observed from the developed nanofibres. In vitro antibacterial test demonstrated that loading of antibiotics in nanofibres not only maintained its antibacterial activity but it got enhanced up to 1.5 to 2-fold. In addition, in vivo study involving rat full-­ thickness wound model demonstrated safety and efficacy of developed teicoplanin-­ loaded nanofibre and significant improvement in wound closure was observed, suggesting the potential of a developed nano drug delivery system in wound healing and local antibiotic delivery [41].

3.3 Lipidic Nanocarriers Cubosomes (Cubic Phase Lipid Nanoparticles) Cubosomes are distinct nanostructures made of excipients such as glyceryl monooleate (GMO) and phytantriol (PHYT), which self-assemble as bicontinuous cubic liquid crystalline phases. Cubosomes with sizes ranging from 100 to 500 nm and characteristic pore sizes of about 5–10 nm offer great potential for incorporating a wide range of actives, including hydrophilic, hydrophobic, and amphiphilic compounds. Solubility enhancement and controlled release of loaded actives can be achieved by using cubosomes as delivery carriers. However, on dividing the bulk cubic phase into distributed nanostructured particles, the surface area of the drug is considerably increased, resulting in a much higher drug diffusion rate into the surrounding media, making them challenging to use as a controlled-release device. In order to achieve controlled release, the properties of cubosomes need to be tailored [42]. In one study, Dyett et al. found that cubosomes are efficient nanocarriers to encapsulate, protect, and potentially deliver ABP. In-situ surface characterisation of model membranes with various compositions, was used to assess the effectiveness of cubosome-mediated ABP delivery. The membrane bilayer was disrupted faster in the case of cubosome-encapsulated ABP compared to free ABP. This finding suggested that cubosome accelerated the process of pore formation in the model

16

B. Karunakaran et al.

membrane and contributed to delivering a sufficient quantity of ABP at a concentration above their water solubility [43]. In a study, Aida KL et  al. developed and characterised a Liquid Crystalline System (LCS) with bioadhesive properties. They incorporated a fragment of D1-23 into LCS, which was further evaluated for cytotoxicity and effect against S. mutans biofilm. Polarised light microscopy, rheology, and in  vitro bioadhesion studies revealed that after incorporation into LCS, both viscosity and bioadhesion increased when it was diluted with artificial saliva and was found effective against S. mutans biofilm. There was an antibiofilm effect when this peptide was incorporated with LCS, indicating that this drug delivery system could be a potential vehicle for CAMP (Cationic Antimicrobial Peptides) delivery [44]. In another study, Meikle T. G. et al. prepared various types of cubosomes by incorporating three antimicrobial peptides: gramicidin A, melittin, and alamethicin. They evaluated each ABP and studied its influence on the structure of the cubosomes. Small-angle X-ray scattering was used to find the optimum peptide loading range that preserves cubic symmetry. Circular dichroism revealed a wide variation in the peptide loading capacity of the various cubosome formulations. For further support, they utilised dynamic light scattering and cryogenic transmission electron microscopy to observe the reduction in particle size and the presence of vesicles. This investigation may help in the field of drug delivery for the development of new encapsulated peptide systems [45]. In a further expansion of the previous study, recently Meikle T. G. et al. tested lipid-based cubic phase nanoparticles-(cubosomes) for the delivery of different AMPs. They used two lipids, which includes monoolein and phytantriol, with each ABP. The variation in peptide hydrophobicity and its charge with lipid composition and various buffer conditions were utilised and further characterised for the stability and loading efficiency of the nanoparticles. They found that the loading efficiency was significantly increased in cubosomes by electrostatic charge manipulation. When these formulations were tested against S. aureus, Bacillus cereus, E. coli, and Pseudomonas aeruginosa, they showed efficient minimum inhibitory concentration (MIC) values as compared to free ABP. This investigation concluded that inhibition of bacterial growth was due to the significant release of ABP from cubosomes to the surrounding media [46]. Solid Lipid Nanoparticles (SLN) SLN provides a versatile advantage for incorporation of ABP by reduction in toxicity due to its biocompatible lipid composition. SLN also help to protect the ABP from chemical and physical degradation and provides the desired sustained release profile. Severino et  al. prepared polymyxin sulphate-loaded SLN (PLX-loaded SLN) by using the double emulsion method (w/o/w). The prepared SLN had a mean size of approximately 200  nm, a polydispersity index of 0.3, a zeta potential of −30 mV and an encapsulation efficiency >90%. The developed SLN showed long-­ term stability for a period of 6 months on storage at room temperature. SLN forms a thin layer across the skin, which avoids water loss and leads to prolonged hydration. The occlusive properties of the SLN were shown to be dependent on the type

Nanocarriers for Delivery of Peptide Antibiotics

17

of lipid, while the antimicrobial properties of PLX-loaded SLN were demonstrated to be effective against P. aeruginosa resistant strains. The crystallinity of the inner SLN matrices was validated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS), implying that these particles have the ability to affect the release profile of the loaded polymyxin sulphate. The results of this study concluded the ability of SLN to retain antimicrobial activity of polymyxin, which can be employed in antibiotic-drug therapy to combat bacterial drug resistance [47]. In another research work, Fumakia and Ho et al., prepared nanocarriers for controlled codelivery of LL37 and serpin A1 (elastase inhibitor) to promote wound healing. For the successful codelivery of two ABPs, they have developed SLN that promoted wound closure in BJ fibroblast cells and keratinocytes and ultimately accelerated wound healing activity. In comparison to LL37 or A1 alone, the SLN formulation enhanced the antibacterial activity against S. aureus and E. coli [48]. Nanostructured Lipid Carriers (NLC) NLCs are second-generation SLNs, which are made up of a mixture of solid and liquid lipids and have a higher drug-loading capacity and stability. NLCs are ideal for cutaneous application and serve as a novel technique for the delivery of proteins and peptides with limited aqueous solubility. Lewies et al. studied the interaction of the ABPs nisin Z and melittin with conventional antibiotics to determine its potential as an adjuvant and further investigated the use of NLCs to enhance antimicrobial activity. Nisin Z has been proven to have both synergistic and additive antibiotic interactions, but melittin, while having additive interactions, also has antagonistic interactions. Furthermore, cytotoxicity experiments revealed that nisin Z is more selective for bacterial cells than melittin. Due to achieving GRAS status and United States Food and Drug Administrarion (USFDA) approval, nisin acts as a great alternative for combination therapy in a clinical setting. At physiological pH, NLC formulations containing nisin Z showed potential in fighting gram-positive bacteria such as S. aureus and S. epidermidis. The findings suggest that nisin Z could be useful as an adjuvant in antimicrobial chemotherapy while helping to fight antibiotic resistance. NLCs have the potential to boost nisin Z’s antibacterial efficacy against gram-positive bacteria that cause skin infections [49]. The effectiveness of LL37 on wound healing was improved by Garica-Orue and co-workers by preparing LL37-loaded NLCs using the melt-emulsification method. The developed NLC-LL37 showed a mean size of 270  nm, a zeta potential of −26 mV and an encapsulation efficiency of 96.4%. The cytotoxicity experiment in human foreskin fibroblasts revealed that NLC-LL37 had no effect on cell viability. In addition, the in vitro antimicrobial assay revealed the NLC-LL37 activity against E. coli. By performing in  vitro and in  vivo studies, they concluded that topical administration of NLC-LL37 improved wound healing in terms of wound closure, reepithelisation grade, and restoration of the inflammatory process as compared to the same concentration of LL37 solution [50].

18

B. Karunakaran et al.

Liposomes Liposomes are promising delivery systems for encapsulation of drugs because of their protective ability and biocompatibility. In a study, Gomaa et al. developed dual coated liposomal formulations for oral administration, of a potent antimicrobial peptide, i.e., microcin J25. They utilised film hydration method for the preparation of liposomes. For increasing the stability and availing gradual release profile from the liposomes they utilised dual layer coating of liposomes by a biopolymer network (pectin) and whey protein isolate (WPI). Layer-by-layer coating was achieved by first coating the liposomes with a layer of negatively charged pectin and then with a second layer of WPI. Prepared liposomes were characterised for their size, charge, encapsulation efficiency, and release. PDI was observed in the range of 0.05–0.2. Uncoated negative liposomes showed a mean diameter of 199 ± 2 nm and zeta potential of −85 ± 2 mV. The coating of liposomes with pectin as the first layer substantially increased the particle size from 199 to 490 nm. This confirms the effective coating of a negatively charged polymer on anionic liposome, whereas the subsequent coating step with WPI caused reduction in particle size to 344 nm due to the compression effect of WPI on interaction with pectin. Finally, it was concluded from their results that dual-coated liposomes are stable and provide additional protection to the loaded microcin during simulated gastrointestinal digestion [51]. Makhathini et al. prepared pH-responsive liposomes for targeted delivery of vancomycin by utilising synthesised novel two-chain fatty acid lipids (FAL). At different pH, uniform size of liposomes was observed from 86.28 ± 11.76 to 282 ± 31.58 nm, with PDI ranging from 0.151 ± 0.016 to 0.204 ± 0.014. Surface charge of the liposomes at pH 7.4 was found to be −11.8 ± 2.99 mV but when pH is reduced to acidic at pH  5.5 then, the surface charge shifted to the positive value, i.e., 3.10 ± 0.583 mV. Finally, they concluded that the change in surface charge is important for the antibacterial activity because the efficient targeting and killing of bacteria is achieved upon the binding of the positively charged liposomes to the negatively charged bacterial cell wall. Flow cytometry results showed a higher rate of killing of methicillin-resistant Staphylococcus aureus (MRSA) cells for (Di-Oleoyl Amino Propionic Acid) DOAPA-VN-Lipo (71.98%) and (Di-Linoleoyl Amino Propionic Acid) DLAPA-VN-Lipo (73.32%). Moreover, in comparison to free vancomycin, the mice treated with the formulations showed a fourfold reduced MRSA recovery [52].

3.4 Self-Assembled Nanocarriers Self-Assembled ABPs Self-assembly of ABP is highly influenced by intermolecular interactions including hydrogen bonding, electrostatic force, hydrophobic interaction and π-π stacking interaction. In aqueous solution, the polar residue of a peptide is observed on the surface, whereas non-polar ones are localised in the interior of the assembly. Due to

Nanocarriers for Delivery of Peptide Antibiotics

19

this condition, the internal structure of a peptide appears to be self-assembled in a hydrophobic microenvironment, which is different from the solution, and thus it could stabilise the peptide secondary structure [53]. Self-assembled peptides are reported to fight against microbial infections. Many peptides, including dermaseptin S9 [54], protegrin-1 [55], as well as bacterially secreted peptides [56], can self-­ assemble and form fibrillar amyloid-like nanostructures that play a role in innate immune activity [57]. Charges and secondary structures of peptides can alter self-­ assembly and thus play a key role in stabilisation. Peptide self-assembly can enhance antibacterial activity. There are few reports suggesting that oligomerisation of peptides can contribute to the antibacterial activity [58]. Human α-defensin 6 (HD6) is a 32-residue cysteine-rich peptide released into the intestinal lumen which, unlike other human α-defensins lacks broad antibacterial activity. However, it exhibits unprecedented self-assembly properties that plays an important role in the host defence function. Monomers of HD6 can self-assemble into the higher-order oligomers known as “nanonets”, which attack the microbes and prevent invasive gastrointestinal pathogens such as Salmonella enterica serovar Typhimurium and Listeria monocytogenes from entering host cells. HD6 thus retains microbes in the lumen allowing other components of the immune system like specialised neutrophils to easily excrete the pathogens out of the immune system. Natural AMPs rarely self-­ assemble into superstructures, which may be due to their highly charged and flexible structures. However, based on their structural characteristics, ABPs could be mutated or modified to obtain self-assembling properties to obtain antibacterial activity [59]. Micelles The use of micelles as nano-based drug delivery systems, particularly for drugs with low water solubility, has garnered a lot of attention recently. They have the ability to solubilise hydrophobic drugs and thus achieve targeted or site-specific drug delivery. Self-assembly of block copolymer into micelles contributes to the designing of a wide range of vesicles, which offer effective control over morphology, surface chemistry, and cargo incorporation. Yuejing Xi, Tao Song et al. have synthesised a PLLA and peptide-based copolymer [PLLA31-b-poly (Phe24-stat-Lys36)], which self-assembled into micelles, having a strong positive charge (+51.8 mV) and shows excellent antibacterial activities against both Gram-negative and Gram-positive bacteria. They concluded that enhancement in the antibacterial activity was due to the cationic groups in the prepared antibacterial micelles, which interact with anionic groups of the bacterial cell wall. Moreover, the TEM image revealed that the micelles act by physically damaging process, which involves the piercing of the bacterial membrane and thus causing death, by outflow of the bacterial content. Micelle shows more potential for designing next-generation antibacterial agents to fight against drug-resistant bacteria [60].

20

B. Karunakaran et al.

3.5 Covalently Conjugated ABPs Covalent Conjugation of ABP with Biomacromolecules Biomacromolecules like hyaluronic acid, alginate, cellulose, or collagen provide efficient dressing in wound healing applications. To enhance the antibacterial activity and reduce the toxicity of the ABP, covalent conjugation of ABP can be used with biomacromolecules. Peptide-polysaccharide conjugates are widely used due to their biodegradability, biocompatibility, and ease of conjugation. In peptide-­ polysaccharide conjugates, peptides play important roles such as crosslinking, self-­ assembly, drug loading, ligand targeting, cleavable linking, and cell adhesion [61]. Cationic chitosan [62], dextrins [63], hyperbranched polyglycerols (HPG) [64] and anionic hyaluronic acid have been used to conjugate ABPs. In one of the studies, Lequeux et al. grafted a hydrophobic and cationic ABP nisin to anionic hyaluronic acid for the preparation of an antimicrobial biopolymer. The resulting biopolymer showed outstanding antibacterial activity in both solution and gel against two gram-­ positive bacteria (S. epidermidis, S. aureus). Notably, biopolymer’s antibacterial efficacy against gram-negative bacteria could only be accomplished by adding EDTA to it, whereas nisin had no effect on gram-negative bacteria [65]. Covalent Conjugation of ABP with Synthetic Polymers Stability, selectivity, and antimicrobial ability are improved by covalently conjugating ABP with synthetic polymers. Coupling and polymerisation are the two methods that are most often used for fabrication of ABP conjugates. Polyethylene glycol (PEG) is mostly used for conjugation because it prolongs the circulation time and reduces cytotoxicity by shielding the positive charge on ABP. PEGylation also improved the stability of ABP, making them more resistant to protease degradation [66]. In a study, Nystrom L. et  al. investigated the local delivery of antibacterial peptides by covalent surface immobilisation of poly (ethyl acrylate-co-methacrylic acid) microgels. The microgels were loaded with the antimicrobial peptide KYE28 and its PEGylated version KYE28PEG for assessing the antimicrobial and anti-­ inflammatory activity. The loading of KYE28 into microgels was enhanced by microgel-peptide electrostatic interactions. However, in the case of KYE28PEG, steric interactions owing to PEG-conjugation opposed its loading and allowed only partial penetration of the peptide into the microgels. Thus, the release of peptide KYE28PEG was comparatively higher at physiological salt concentrations. Further, in  vitro studies confirmed the antimicrobial activity of the released peptides on microgel-modified surfaces. The results of this investigation showed that surface-­ bound microgels are beneficial for local drug delivery of host defence peptides, and also emphasised the importance of achieving significant peptide surface loading for optimal biological effects [67].

Nanocarriers for Delivery of Peptide Antibiotics

21

4 Opportunities and Challenges for Nanocarrier-Based ABP Delivery Multiple clinical trials are going on to translate various nanocarrier-based ABP into clinical practice. In past, some ABP failed in clinical trials including NVB-302 (phase I), POL7080 (phase II), Iseganan, Omiganan, and Surotomycin at phase III [70]. These failures made the efforts turn into topical application of ABP over the parenteral route. There is an opportunity to explore various technological advancements in interdisciplinary aspects for improving the clear understanding of several modes of action for ABPs, novel formulation strategies, and advanced chemical synthesis schemes. However, there are some potential challenges that need to be considered in the life cycle of peptide-based product development. Both gram-­positive and gram-negative bacteria possess various strategies of resistance towards antimicrobial peptides such as removal by efflux pumps, alteration of membrane fluidity or degradation by secreted proteins that need consideration [71]. In practical perspective, processing hurdles includes selection of preparation method for nanocarriers, peptide exposure to organic solvents, shear stress induced by either sonication or mechanical homogenisation, which can alter morphology and activity of peptide [72]. Loading of larger molecules like proteins and peptides (ABP) in nanocarriers is limited, and thus, effective drug loading methods should be optimised (e.g., by altering electrostatic effects or increasing hydrophobic interactions) [73]. Further, as stated by Gustafson et al., the non-specific uptake of ABP-loaded nanoparticles by phagocytes can result in degradation and clearance without exerting antimicrobial effects. This issue is particularly prominent when nanoparticles are administered intravenously, and it can be resolved by coating nanoparticles with a stealth coating [e.g., polyethylene glycol, poly (zwitterions)] [74]. The mechanisms of antibacterial activity of different ABPs are different. Because some ABPs like LL37, melittin, and magainin damage bacterial cell membranes, they must be released outside the bacterial cell membrane to have potential therapeutic effects. However, the nanoparticles can be uptaken by microorganisms in some cases, resulting in intracellular ABP release. This issue can be resolved by developing hybrid systems including ABP-loaded nanoparticles into a hydrogel that provides a steady and controlled release of ABP to the target site, resulting in promising antibacterial effects. Moreover, the strength, weakness, opportunities, and threats (SWOT) analysis of nanocarriers-based ABP is summarised in Fig. 3.

5 Commercialisation and Clinical Development of ABPs It is important to note that in the past few years, ABPs have crossed longer ways to reach at the product development stage. Numerous preclinical trials are going on to investigate the potential therapeutics for the prevention and treatment of various bacterial infections. For example, PL-5 possesses an alpha-helical structure and was

22

B. Karunakaran et al.

Fig. 3  SWOT analysis of nanocarrier-based ABPs [75]

developed by Prote Light Pharmaceuticals, which received approval from the China Food and Drug Administration (CFDA) for application at a clinical stage in China. The literature suggested PL-5 showed less toxicity and high potency against a broad spectrum of drug-resistance bacteria. In addition, this peptide molecule could provide synergistic effects with conventional antibiotics for improved antibacterial activity against both gram-positive and negative bacteria [76]. However, the identification of natural ABPs is the primary step of drug development, and further modification and optimisation are in the pipeline steps of drug development. Various industries, including Magainin Pharmaceuticals, Micrologix Biotech, and IntraBiotics, have started developing different therapeutic peptides from their natural progenitors by using various amino acids. The first cationic peptide (ABP) was pexiganan (MSI-78), which had a synthetic 22-amino-acid version of the amphibian peptide magainin 2. Although pexiganan was associated with few toxicities, it served as an efficient therapeutic in the treatment of wound healing, and it has now completed phase III clinical trial [77]. One of the injectable formulations of protein fragment rBPI21 (NEUPREX®) showed higher efficacy in phase III clinical trial in meningococcal disease and endotoxin-mediated complications [78]. An anti-­ infective peptide named as MX-226, also known as CPI-226, has been proved efficacious in phase III clinical study. It is a peptide based on bovine indolicidin that was developed to prevent central venous catheter contamination. It has shown a 49% reduction in contamination on catheter sites and a 21% reduction in catheter colonisation. The other clinical trials include the successful completion of phase II clinical trials of indolicidin-based MX594AN (Migenix) for mild-to-moderate acne and completed phase I trials of human-lactoferricin-based peptide hLF1-11 for preventing infections in patients undergoing allogeneic stem cell transplantation [79, 80] (Table 3).

Friulimicin

Murepavadin (POL7080)

NCT00492271

EUCTR2017-003933-­ 27-EE

Intradermal

II

I

I/II

Α-helical peptide

Melittin

Human cathelicidin

II

NCT02364349; NCT01526031

Topical

Lipopeptide

III

Intravenous

Analogue of Protegrin Intravenous

Cyclic lipopeptide

Intravenous

Intravenous

Daptomycin NCT01922911; NCT00093067; NCT01104662; NCT02972983 EUCTR2012-002100-41 LL-37

Cyclic Polypeptide

III

Topical

Polymyxin E (colistin)

Cyclic Polypeptide

NCT01292031; NCT02573064

III

Polymyxin B

Polycyclic peptide

III

Gramicidin

Mechanism of action Depolarisation of cell membrane Membrane disruption/ immunomodulation Membrane disruption/ immunomodulation Membrane disruption/ immunomodulation Membrane disruption/ immunomodulation

Membrane disruption/ immunomodulation Inflammation Membrane disruption/ immunomodulation MRSA/pneumonia Membrane disruption P. aeruginosa, K. Binding to LptD pneumoniae

Leg ulcers

Skin Infection/ Bacteraemia

A. Baumanni/ pneumonia

Gram-negative bacteria

Type of Targeting moiety/ administration Specific indication Oral Gram-positive bacteria Topical Infected wounds and ulcers

NCT00490477; NCT00534391

Clinical trial ID NCT02928042; NCT02467972 NCT00534391

Clinical trial Phase Type of peptide – Polycyclic antibiotic

Name of peptide Nisin

Table 3  Clinical development of ABPs

[84]

[85]

[86]

1155

1621

4491

1553.8

1303.5

(continued)

[89]

[88]

[87]

[83]

1204

2846.5

[82]

1882

Molecular weight (g/ mol) References 3354 [81]

Nanocarriers for Delivery of Peptide Antibiotics 23

I/II

II

NVB-302

OP-145

P113 (PAC-113)

LTX-109

EA-230

ISRCTN40071144

ISRCTN84220089

NCTO0659971

NCT01803035; NCTO1158235 NCT03145220

II

I/II

I

III

III

III

III

III

Ear drops

Oral

Topical

Topical

Oligopeptide

Synthetic tripeptide

Intravenous

Topical

Fragment of Histatin-5 Mouth rinse

Derivative of LL-37

Lantibiotic

Derivative of indolicidin

Derivative of BPI

Analogue of Magainin Topical

Sepsis

MRSA impetigo

Oral candidiasis

Chronic middle ear infection

C. difficile

Impetigo/acne rosacea Antisepsis/ catheter infection

2477.2

1680.8

1900.3

Membrane 1779.2 disruption/ immunomodulation Inhibition of cell 1754.0 wall Membrane 3092.8 disruption/ immunomodulation Membrane 1564.8 disruption/ immunomodulation Membrane 788.1 disruption Immunomodulation 415.5

[100]

[99]

[98]

[97]

[96]

[95]

[94]

[93]

[92]

[91]

Molecular weight (g/ mol) References 21000 [90]

Immunomodulation 1158.4

Mechanism of action Membrane disruption Membrane disruption Membrane disruption Diabetic foot ulcer Membrane disruption/ immunomodulation

Type of Targeting moiety/ administration Specific indication Intravenous Paediatric meningococcemia Analogue of protegrin Topical Pneumonia/oral mucositis Cyclic lipopeptide Oral C. difficile

Clinical trial Phase Type of peptide III Derivative of BPI

NCTO0231153; NCT00608959

Name of peptide Neuprex® (rBPI21) Iseganan (IB-367) Surotomycin (CB-315) Pexiganan (MSI-78)

XOMA-629 (XMP629) Omiganan (MBI-226)

NCT00563394; NCT00563433; NCT01590758; NCT01594762

NCT00118781; NCT00022373 NCT01597505

Clinical trial ID NCT00462904

Table 3 (continued)

24 B. Karunakaran et al.

NCTO1447017

Delmitide (RDP58) DPK-060

ISRCTN84220089

II

II

II

I/III

Mel4

LFF571

II/III

Melamine

Derivative of Kininogen

Derivative of melamine Semisynthetic thiopeptide Derivative of HLA

Chimeric peptide

Synthetic peptide

III

NCTO1232595

Mouth wash

Intravenous

Ear drops

Topical

Oral

Topical

Topical

Topical

Intravenous

Inflammatory bowel disease Acute external otitis

Necrotic tissue infection Burn wound infections Contact lenses microbials Contact lenses microbials C. difficile

Streptococcus mutans Fungal nail infection C. difficile, VRE

Bacterial/fungal infections

(continued)

[68] Membrane disruption/ immunomodulation

2503.2

[110]

[109]

[108]

[107]

[106]

[105]

[104]

[103]

[102]

[111]

1366.6

2347.8

2786.6

2775.4

1037

2568.1

1093.3

4077.4

1373.7

Immunomodulation 1228.6

Membrane disruption Membrane disruption Membrane disruption Inhibition of protein

Membrane disruption/ immunomodulation Membrane disruption Membrane disruption Inhibition of cell wall Immunomodulation

Molecular weight (g/ Type of Targeting moiety/ Mechanism of mol) References administration Specific indication action Oral rinse Oral mucositis Immunomodulation 553.7 [101]

Cyclic Cationic Topical peptide Glycolipodepsipeptide Oral

D2A21

II

Synthetic peptide

Fragment of human lactoferrin

Synthetic peptide

Novexatin

NCT02933879 (NP213)

II

I/II

Clinical trial Phase Type of peptide III Analogue of IDR-1

Ramoplan III (NTI-851) p2TA (AB103) III

C16G2

NCTO3004365

NCTO0430469

Clinical trial ID NCT03237325

Name of peptide SGX942 (Dusquetide) hLF1-11

Nanocarriers for Delivery of Peptide Antibiotics 25

NCT00763477

II XF-73 (Exeporfinium chloride) CZEN-002 II Ghrelin II

NCT03915470

I

I

IDR-1

I/II

Wap-8294A2 (Lotilibcin) PL-5

II

PMX-30063

NCT01211470; NCT02052388

II

II

Bactenecin

intravenous

Topical

Topical

Topical Intravenous

Derivative of o-MSH Endogenous peptide Produced by Lysobacter species Synthetic peptide

Topical

Intravenous

Intravenous

Infection prevention

Antifungal Chronic respiratory infection Gram-positive bacteria Skin infections

Acute bacterial skin infection Staphylococcal infection

Post-surgical organ failure

Type of Targeting moiety/ administration Specific indication Oral Bacterial skin infection Topical

Derivative of porphyrin

Defensin mimetic

Analogue of Lactoferrin Derivative of o-MSH

Clinical trial Phase Type of peptide II Synthetic hydrazide

AP-214

Name of peptide GSK1322322 (Lanopepden) PXLO1

NCT00903604

NCTO1022242

Clinical trial ID NCTO1209078

Table 3 (continued)

[115]

936.9

Membrane 1562.8 disruption 2933.5 Membrane disruption Immunomodulation 1391.7

[121]

[120]

[119]

[117] [118]

[116]

[114]

2433.9

765.8

[113]

3061.6

Molecular weight (g/ mol) References 479.3 [112]

Immunomodulation 971.2 Immunomodulation 3314.9

Membrane disruption/ immunomodulation Membrane disruption/ immunomodulation Membrane disruption

Mechanism of action Peptide deformylase inhibitor Immunomodulation

26 B. Karunakaran et al.

Nanocarriers for Delivery of Peptide Antibiotics

27

6 Summary Nanocarrier-based ABP delivery is an emerging concept for the treatment of bacterial infections. Nanocarriers possess unique properties and functions suitable for ABP delivery. However, there are many challenges to incorporating ABPs in nanocarriers due to some limitations, which includes low entrapment efficiency and low drug loading, selection of suitable carrier system and achieving desired ABP release rate, which makes the development process of ABP-loaded nanosystem critical. However, enormous findings have been reported for the optimisation of nanocarrier-­ based drug delivery of ABPs. So far, ABP-loaded nanocarrier-based formulation is not available in the market; however, few are in clinical trials. Still, there is room for ABP-loaded nanocarriers to be thoroughly researched and developed in the future. In addition, in vivo investigations are needed to clearly understand the physiological and immunological responses of ABP exposure. These studies can eventually lead to the development of microenvironment/stimuli-responsive, smart, and safe nanocarrier-­based ABP delivery approaches for the effective treatment of bacterial infections. Future investments in the development of natural peptides and nanocarrier-­ based delivery systems from natural polymers might have a new landscape.

References 1. What are antibiotics and how do they work? | Microbiology Society. https://microbiologysociety.org/members-­outreach-­resources/outreach-­resources/antibiotics-­unearthed/antibiotics-­ and-­antibiotic-­resistance/what-­are-­antibiotics-­and-­how-­do-­they-­work.html. Accessed 8 Jul 2022. 2. Rima M, Fajloun Z, Sabatier JM, Bechinger B, Naas T. Antimicrobial peptides: a potent alternative to antibiotics. Antibiotics. 2021;10:1095. https://doi.org/10.3390/antibiotics10091095. 3. World Health Organization. Antimicrobial resistance. https://www.who.int/news-­room/fact-­ sheets/detail/antimicrobial-­resistance. Accessed 1 Jun 2022. 4. Llor C, Bjerrum L.  Antimicrobial resistance: risk associated with antibiotic overuse and initiatives to reduce the problem. Ther Adv Drug Saf. 2014;5:229. https://doi. org/10.1177/2042098614554919. 5. Makabenta JMV, Nabawy A, Li CH, Schmidt-Malan S, Patel R, Rotello VM. Nanomaterial-­ based therapeutics for antibiotic-resistant bacterial infections. Nat Rev Microbiol. 2021;19:23. https://doi.org/10.1038/s41579-­020-­0420-­1. 6. Saini R, Saini S, Sharma S.  Nanotechnology: the future medicine. J Cutan Aesthet Surg. 2010;3:32. https://doi.org/10.4103/0974-­2077.63301. 7. Greco I, Molchanova N, Holmedal E, Jenssen H, Hummel BD, Watts JL, et al. Correlation between hemolytic activity, cytotoxicity and systemic in vivo toxicity of synthetic antimicrobial peptides. Sci Rep. 2020;10:1–13. https://doi.org/10.1038/s41598-­020-­69995-­9. 8. Mahlapuu M, Håkansson J, Ringstad L, Björn C. Antimicrobial peptides: an emerging category of therapeutic agents. Front Cell Infect Microbiol. 2016;6:194. https://doi.org/10.3389/ fcimb.2016.00194.

28

B. Karunakaran et al.

9. Scocchi M, Mardirossian M, Runti G, Benincasa M. Non-membrane permeabilizing modes of action of antimicrobial peptides on bacteria. Curr Top Med Chem. 2015;16:76–88. https:// doi.org/10.2174/1568026615666150703121009. 10. Huan Y, Kong Q, Mou H, Yi H.  Antimicrobial peptides: classification, design, application and research progress in multiple fields. Front Microbiol. 2020;11:2559. https://doi. org/10.3389/fmicb.2020.582779. 11. Hancock REW, Chapple DS.  Peptide antibiotics. Antimicrob Agents Chemother. 1999;43:1317–23. https://doi.org/10.1128/aac.43.6.1317. 12. Nguyen R, Khanna NR, Safadi AO, Sun Y. Bacitracin Topical. In: statPearls. Treasure Island: StatPearls Publishing; 2021. 13. Tedesco KL, Rybak MJ.  Daptomycin. Pharmacotherapy. 2004;24:41–57. https://doi. org/10.1592/phco.24.1.41.34802. 14. Cada D, Ingram K, Baker D.  Formulary drug reviews: Dalbavancin. Hosp Pharm. 2014;49:851–61. https://doi.org/10.1310/hpj4909-­851. 15. Corey GR, Kabler H, Mehra P, Gupta S, Overcash JS, Porwal A, et al. Single-dose oritavancin in the treatment of acute bacterial skin infections. N Engl J Med. 2014;370:2180–90. https:// doi.org/10.1056/nejmoa1310422. 16. U.S. Food and Drug Administration. VIALS VANCOCIN® HCl Vancomycin hydrochloride for injection USP for intravenous use. https://www.accessdata.fda.gov/drugsatfda_docs/ label/2021/060180s049lbl.pdf. Accessed 9 Jul 2022. 17. Goldstein BP, Rosina R, Parenti F. Teicoplanin. In: Nagarajan R, editor. Glycopeptide antibiotics. Boca Raton: CRC Press; 2020. p. 273–308. 18. Higgins DL, Chang R, Debabov DV, Leung J, Wu T, Krause KM, et al. Telavancin, a multifunctional lipoglycopeptide, disrupts both cell wall synthesis and cell membrane integrity in methicillin-resistant staphylococcus aureus. Antimicrob Agents Chemother. 2005;49:1127. https://doi.org/10.1128/aac.49.3.1127-­1134.2005. 19. Otvos L.  Antibacterial peptides and proteins with multiple cellular targets. J Pept Sci. 2005;1:697–706. https://doi.org/10.1002/psc.698. 20. Cudic M, Otvos L Jr. Intracellular targets of antibacterial peptides. Curr Drug Targets. 2002;3:101–6. https://doi.org/10.2174/1389450024605445. 21. Eckert R, Sullivan R, Shi W.  Targeted antimicrobial treatment to re-establish a healthy microbial flora for long-term protection. Adv Dent Res. 2012;24:94–7. https://doi. org/10.1177/0022034512453725. 22. Biswaro LS, da Sousa MGC, Rezende TMB, Dias SC, Franco OL. Antimicrobial peptides and nanotechnology, recent advances and challenges. Front Microbiol. 2018;9:855. https:// doi.org/10.3389/fmicb.2018.00855. 23. Storm G, Belliot SO, Daemen T, Lasic DD. Surface modification of nanoparticles to oppose uptake by the mononuclear phagocyte system. Adv Drug Deliv Rev. 1995;17:31–48. https:// doi.org/10.1016/0169-­409X%2895%2900039-­A. 24. Patra JK, Das G, Fraceto LF, Campos EVR, Rodriguez-Torres MDP, Acosta-Torres LS, et  al. Nano based drug delivery systems: recent developments and future prospects. J Nanobiotechnol. 2018;16:1–33. https://doi.org/10.1186/s12951-­018-­0392-­8. 25. Fromen CA, Rahhal TB, Robbins GR, Kai MP, Shen TW, Luft JC, et  al. Nanoparticle surface charge impacts distribution, uptake and lymph node trafficking by pulmonary antigen-­ presenting cells. Nanomedicine. 2016;12:677–87. https://doi.org/10.1016/j. nano.2015.11.002. 26. Thapa RK, Diep DB, Tønnesen HH. Nanomedicine-based antimicrobial peptide delivery for bacterial infections: recent advances and future prospects. J Pharm Investig. 2021;5:377–98. https://doi.org/10.1007/s40005-­021-­00525-­z. 27. Tenland E, Pochert A, Krishnan N, Rao KU, Kalsum S, Braun K, et al. Effective delivery of the anti-mycobacterial peptide NZX in mesoporous silica nanoparticles. PLoS One. 2019;14:e0212858. https://doi.org/10.1371/journal.pone.0212858.

Nanocarriers for Delivery of Peptide Antibiotics

29

28. Häffner SM, Parra-Ortiz E, Browning KL, Jørgensen E, Skoda MWA, Montis C, et  al. Membrane interactions of virus-like mesoporous silica nanoparticles. ACS Nano. 2021;15:6787–800. https://doi.org/10.1021/acsnano.0c10378. 29. Yu Q, Deng T, Lin FC, Zhang B, Zink JI. Supramolecular assemblies of heterogeneous mesoporous silica nanoparticles to co-deliver antimicrobial peptides and antibiotics for synergistic eradication of pathogenic biofilms. ACS Nano. 2020;14:5926–37. https://doi.org/10.1021/ acsnano.0c01336. 30. Gallo J, Holinka M, Moucha CS. Antibacterial surface treatment for orthopaedic implants. Int J Mol Sci. 2014;15:13849–80. https://doi.org/10.3390/ijms150813849. 31. Pihl M, Galli S, Jimbo R, Andersson M.  Osseointegration and antibacterial effect of an antimicrobial peptide releasing mesoporous titania implant. J Biomed Mater Res B Appl Biomater. 2021;109:1787–95. https://doi.org/10.1002/jbm.b.34838. 32. Kamaly N, Yameen B, Wu J, Farokhzad OC. Degradable controlled-release polymers and polymeric nanoparticles: mechanisms of controlling drug release. Chem Rev. 2016;116:2602–63. https://doi.org/10.1021/acs.chemrev.5b00346. 33. Walkenhorst WF, Klein JW, Vo P, Wimley WC. pH dependence of microbe sterilization by cationic antimicrobial peptides. Antimicrob Agents Chemother. 2013;57:3312–20. https:// doi.org/10.1128/aac.00063-­13. 34. Gómez-Sequeda N, Ruiz J, Ortiz C, Urquiza M, Torres R. Potent and specific antibacterial activity against Escherichia coli O157:H7 and methicillin resistant Staphylococcus aureus (MRSA) of G17 and G19 peptides encapsulated into Poly-Lactic-Co-Glycolic Acid (PLGA) nanoparticles. Antibiotics. 2020;9:384. https://doi.org/10.3390/antibiotics9070384. 35. Atay HY.  Antibacterial activity of chitosan-based systems. Funct Chitosan. 2020:457–89. https://doi.org/10.1007/978-­981-­15-­0263-­7_15. 36. Sun T, Zhan B, Zhang W, Qin D, Xia G, Zhang H, et al. Carboxymethyl chitosan nanoparticles loaded with bioactive peptide OH-CATH30 benefit nonscar wound healing. Int J Nanomedicine. 2018;13:5771–86. https://doi.org/10.2147/IJN.S156206. 37. Sharma R, Raghav R, Priyanka K, Rishi P, Sharma S, Srivastava S, et  al. Exploiting chitosan and gold nanoparticles for antimycobacterial activity of in silico identified antimicrobial motif of human neutrophil peptide-1. Sci Rep. 2019;9:1. https://doi.org/10.1038/ s41598-­019-­44256-­6. 38. Heunis TDJ, Smith C, Dicks LMT. Evaluation of a nisin-eluting nanofiber scaffold to treat staphylococcus aureus-induced skin infections in mice. Antimicrob Agents Chemother. 2013;57:3928–35. https://doi.org/10.1128/aac.00622-­13. 39. He Y, Jin Y, Wang X, Yao S, Li Y, Wu Q, et  al. An antimicrobial peptide-loaded gelatin/ chitosan nanofibrous membrane fabricated by sequential layer-by-layer electrospinning and electrospraying techniques. Nano. 2018;8:327. https://doi.org/10.3390/nano8050327. 40. Román JT, Fuenmayor CA, Dominguez CMZ, Clavijo-Grimaldo Di, Acosta M, García-­ Castañeda JE, et  al. Pullulan nanofibers containing the antimicrobial palindromic peptide LfcinB (21-25)Pal obtained via electrospinning. RSC Adv. 2019;9:20432–8. https://doi. org/10.1039/C9RA03643A. 41. Amiri N, Ajami S, Shahroodi A, Jannatabadi N, Amiri Darban S, Fazly Bazzaz BS, et al. Teicoplanin-loaded chitosan-PEO nanofibers for local antibiotic delivery and wound healing. Int J Biol Macromol. 2020;162:645–56. https://doi.org/10.1016/j.ijbiomac.2020.06.195. 42. Karami Z, Hamidi M. Cubosomes: remarkable drug delivery potential. Drug Discov Today. 2016;21:789–801. https://doi.org/10.1016/j.drudis.2016.01.004. 43. Dyett BP, Yu H, Lakic B, Silva N, Dahdah A, Bao L, et al. Delivery of antimicrobial peptides to model membranes by cubosome nanocarriers. J Colloid Interface Sci. 2021;600:14–22. https://doi.org/10.1016/j.jcis.2021.03.161. 44. Aida KL, Kreling PF, Caiaffa KS, Calixto GMF, Chorilli M, Spolidorio DMP, et  al. Antimicrobial peptide-loaded liquid crystalline precursor bioadhesive system for the prevention of dental caries. Int J Nanomedicine. 2018;13:3081–91. https://doi.org/10.2147/IJN. S155245.

30

B. Karunakaran et al.

45. Meikle TG, Zabara A, Waddington LJ, Separovic F, Drummond CJ, Conn CE. Incorporation of antimicrobial peptides in nanostructured lipid membrane mimetic bilayer cubosomes. Colloids Surf B: Biointerfaces. 2017;152:143–51. https://doi.org/10.1016/j. colsurfb.2017.01.004. 46. Meikle TG, Dharmadana D, Hoffmann SV, Jones NC, Drummond CJ, Conn CE. Analysis of the structure, loading and activity of six antimicrobial peptides encapsulated in cubic phase lipid nanoparticles. J Colloid Interface Sci. 2021;587:90–100. https://doi.org/10.1016/j. jcis.2020.11.124. 47. Severino P, Silveira EF, Loureiro K, Chaud MV, Antonini D, Lancellotti M, et al. Antimicrobial activity of polymyxin-loaded solid lipid nanoparticles (PLX-SLN): characterization of physicochemical properties and in vitro efficacy. Eur J Pharm Sci. 2017;106:177–84. https://doi. org/10.1016/j.ejps.2017.05.063. 48. Fumakia M, Ho EA. Nanoparticles encapsulated with LL37 and serpin A1 promotes wound healing and synergistically enhances antibacterial activity. Mol Pharm. 2016;13:2318–31. https://doi.org/10.1021/acs.molpharmaceut.6b00099. 49. Lewies A, Wentzel JF, Jordaan A, Bezuidenhout C, du Plessis LH.  Interactions of the antimicrobial peptide nisin Z with conventional antibiotics and the use of nanostructured lipid carriers to enhance antimicrobial activity. Int J Pharm. 2017;526:244–53. https://doi. org/10.1016/j.ijpharm.2017.04.071. 50. Garcia-Orue I, Gainza G, Girbau C, Alonso R, Aguirre JJ, Pedraz JL, et al. LL37 loaded nanostructured lipid carriers (NLC): a new strategy for the topical treatment of chronic wounds. Eur J Pharm Biopharm. 2016;108:310–6. https://doi.org/10.1016/j.ejpb.2016.04.006. 51. Gomaa AI, Martinent C, Hammami R, Fliss I, Subirade M.  Dual coating of liposomes as encapsulating matrix of antimicrobial peptides: development and characterization. Front Chem. 2017;5:103. https://doi.org/10.3389/fchem.2017.00103. 52. Makhathini SS, Kalhapure RS, Jadhav M, Waddad AY, Gannimani R, Omolo CA, et al. Novel two-chain fatty acid-based lipids for development of vancomycin pH-responsive liposomes against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). J Drug Target. 2019;27:1094–107. https://doi.org/10.1080/1061186x.2019.1599380. 53. Li T, Lu XM, Zhang MR, Hu K, Li Z.  Peptide-based nanomaterials: self-assembly, properties and applications. Bioact Mater. 2022;11:268–82. https://doi.org/10.1016/j. bioactmat.2021.09.029. 54. Auvynet C, Amri C, Lacombe C, Bruston F, Bourdais J, Nicolas P, et al. Structural requirements for antimicrobial versus chemoattractant activities for dermaseptin S9. FEBS J. 2008;275:4134–51. https://doi.org/10.1111/j.1742-­4658.2008.06554.x. 55. Jang H, Arce FT, Mustata M, Ramachandran S, Capone R, Nussinov R, et al. Antimicrobial Protegrin-1 forms amyloid-like fibrils with rapid kinetics suggesting a functional link. Biophys J. 2011;100:1775–83. https://doi.org/10.1016/j.bpj.2011.01.072. 56. Tayeb-Fligelman E, Tabachnikov O, Moshe A, Goldshmidt-Tran O, Sawaya MR, Coquelle N, et al. The cytotoxic Staphylococcus aureus PSMα3 reveals a cross-α amyloid-like fibril. Science. 2017;355:831–3. https://doi.org/10.1126/science.aaf4901. 57. Schnaider L, Brahmachari S, Schmidt NW, Mensa B, Shaham-Niv S, Bychenko D, et  al. Self-assembling dipeptide antibacterial nanostructures with membrane disrupting activity. Nat Commun. 2017;8:1–10. https://doi.org/10.1038/s41467-­017-­01447-­x. 58. Sancho-Vaello E, François P, Bonetti EJ, et al. Structural remodeling and oligomerization of human cathelicidin on membranes suggest fibril-like structures as active species. Sci Rep. 2017;7:15371. https://doi.org/10.1038/s41598-­017-­14206-­1. 59. Chairatana P, Nolan EM.  Human α-Defensin 6: a small peptide that self-assembles and protects the host by entangling microbes. Acc Chem Res. 2017;50:960–7. https://doi. org/10.1021/acs.accounts.6b00653. 60. Xi Y, Song T, Tang S, Wang N, Du J.  Preparation and antibacterial mechanism insight of polypeptide-based micelles with excellent antibacterial activities. Biomacromolecules. 2016;17:3922–30. https://doi.org/10.1021/acs.biomac.6b01285.

Nanocarriers for Delivery of Peptide Antibiotics

31

61. Song HQ, Fan Y, Hu Y, Cheng G, Xu FJ.  Polysaccharide–peptide conjugates: a versatile material platform for biomedical applications. Adv Funct Mater. 2021;31:2005978. https:// doi.org/10.1002/adfm.202005978. 62. Sahariah P, Sørensen KK, Hjálmarsdóttir MA, Sigurjónsson ÓE, Jensen KJ, Másson M, et al. Antimicrobial peptide shows enhanced activity and reduced toxicity upon grafting to chitosan polymers. Chem Commun. 2015;51:11611–4. https://doi.org/10.1039/C5CC04010H. 63. Ferguson EL, Azzopardi E, Roberts JL, Walsh TR, Thomas DW. Dextrin-colistin conjugates as a model bioresponsive treatment for multidrug resistant bacterial infections. Mol Pharm. 2014;11:4437–47. https://doi.org/10.1021/mp500584u. 64. Kumar P, Takayesu A, Abbasi U, Kalathottukaren MT, Abbina S, Kizhakkedathu JN, et al. Antimicrobial peptide-polymer conjugates with high activity: influence of polymer molecular weight and peptide sequence on antimicrobial activity, proteolysis, and biocompatibility. ACS Appl Mater Interfaces. 2017;9:37575–86. https://doi.org/10.1021/acsami.7b09471. 65. Lequeux I, Ducasse E, Jouenne T, Thebault P. Addition of antimicrobial properties to hyaluronic acid by grafting of antimicrobial peptide. Eur Polym J. 2014;51:182–90. https://doi. org/10.1016/j.eurpolymj.2013.11.012. 66. Cui Q, Xu QJ, Liu L, Guan LL, Jiang XY, Inam M, et al. Preparation, characterization and pharmacokinetic study of N-Terminal PEGylated D-Form antimicrobial peptide OM19r-8. J Pharm Sci. 2021;110:1111–9. https://doi.org/10.1016/j.xphs.2020.10.048. 67. Nyström L, Strömstedt AA, Schmidtchen A, Malmsten M. Peptide-loaded microgels as antimicrobial and anti-inflammatory surface coatings. Biomacromolecules. 2018;19:3456–66. https://doi.org/10.1021/acs.biomac.8b00776. 68. Håkansson J, Ringstad L, Umerska A, Johansson J, Andersson T, Boge L, et  al. Characterization of the in  vitro, ex  vivo, and in  vivo efficacy of the antimicrobial peptide DPK-060 used for topical treatment. Front Cell Infect Microbiol. 2019;9:174. https://doi. org/10.3389/fcimb.2019.00174. 69. Almaaytah A, Mohammed GK, Abualhaijaa A, Al-Balas Q.  Development of novel ultrashort antimicrobial peptide nanoparticles with potent antimicrobial and antibiofilm activities against multidrug-resistant bacteria. Drug Des Dev Ther. 2017;11:3159–70. https://doi. org/10.2147/dddt.s147450. 70. Sierra JM, Fusté E, Rabanal F, Vinuesa T, Viñas M. An overview of antimicrobial peptides and the latest advances in their development. Expert Opin Biol Ther. 2017;17:663–76. https:// doi.org/10.1080/14712598.2017.1315402. 71. Joo HS, Fu CI, Otto M. Bacterial strategies of resistance to antimicrobial peptides. Philos Trans R Soc Lond Ser B Biol Sci. 2016;371:20150292. https://doi.org/10.1098/rstb.2015.0292. 72. Mohammadi-Samani S, Taghipour B. PLGA micro and nanoparticles in delivery of peptides and proteins; problems and approaches. Pharm Dev Technol. 2015;20:385–93. https://doi. org/10.3109/10837450.2014.882940. 73. Fam SY, Chee CF, Yong CY, Ho KL, Mariatulqabtiah AR, Tan WS. Stealth coating of nanoparticles in drug-delivery systems. Nano. 2020;10:787. https://doi.org/10.3390/nano10040787. 74. Gustafson HH, Holt-Casper D, Grainger DW, Ghandehari H. Nanoparticle uptake: the phagocyte problem. Nano Today. 2015;10:487–510. https://doi.org/10.1016/j.nantod.2015.06.006. 75. Mahlapuu M, Björn C, Ekblom J. Antimicrobial peptides as therapeutic agents: opportunities and challenges. Crit Rev Biotechnol. 2020;40:978–92. https://doi.org/10.1080/0738855 1.2020.1796576. 76. Feng Q, Huang Y, Chen M, Li G, Chen Y. Functional synergy of α-helical antimicrobial peptides and traditional antibiotics against Gram-negative and Gram-positive bacteria in  vitro and in  vivo. Eur J Clin Microbiol Infect Dis. 2015;34:197–204. https://doi.org/10.1007/ s10096-­014-­2219-­3. 77. ClinicalTrials.gov Search of: active, not recruiting, completed, terminated studies | pexiganan (MSI-78)  - list results. https://www.clinicaltrials.gov/ct2/results?cond=pexiganan+%2 8MSI-­78%29&Search=Apply&recrs=d&recrs=h&recrs=e&age_v=&gndr=&type=&rslt. Accessed 8 Jul 2022.

32

B. Karunakaran et al.

78. Iwuji K, Larumbe-Zabala E, Bijlani S, Nugent K, Kanu A, Manning E, et  al. Prevalence of bactericidal/permeability-increasing protein autoantibodies in cystic fibrosis patients: systematic review and meta-analysis. Pediatr Allergy Immunol Pulmonol. 2019;32:45–51. https://doi.org/10.1089/ped.2018.0970. 79. AdisInsight: Omiganan  - Cutanea Life Sciences. https://adisinsight.springer.com/ drugs/800011276. Accessed 8 Jul 2022. 80. Marr A, Gooderham W, Hancock R.  Antibacterial peptides for therapeutic use: obstacles and realistic outlook. Curr Opin Pharmacol. 2006;6:468–72. https://doi.org/10.1016/j. coph.2006.04.006. 81. Prince A, Sandhu P, Kumar P, Dash E, Sharma S, Arakha M, et al. Lipid-II independent antimicrobial mechanism of nisin depends on its crowding and degree of oligomerization. Sci Rep. 2016;6:1–15. https://doi.org/10.1038/srep37908. 82. David JM, Rajasekaran AK.  Gramicidin A: a new mission for an old antibiotic. J Kidney Cancer VHL. 2015;2:15–24. https://doi.org/10.15586/jkcvhl.2015.21. 83. Morrison DC, Jacobs DM.  Binding of polymyxin B to the lipid A portion of bacterial lipopolysaccharides. Immunochemistry. 1976;13:813–8. https://doi. org/10.1016/0019-­2791(76)90181-­6. 84. Yu Z, Qin W, Lin J, Fang S, Qiu J. Antibacterial mechanisms of polymyxin and bacterial resistance. Biomed Res Int. 2015;2015:679109. https://doi.org/10.1155/2015/679109. 85. Taylor SD, Palmer M.  The action mechanism of daptomycin. Bioorg Med Chem. 2016;24:6253–68. https://doi.org/10.1016/j.bmc.2016.05.052. 86. Brown KL, Poon GFT, Birkenhead D, Pena OM, Falsafi R, Dahlgren C, et al. Host defense peptide LL-37 selectively reduces proinflammatory macrophage responses. J Immunol. 2011;186:5497–505. https://doi.org/10.4049/jimmunol.1002508. 87. Lee G, Bae H. Anti-inflammatory applications of melittin, a major component of bee venom: detailed mechanism of action and adverse effects. Molecules. 2016;21:616. https://doi. org/10.3390/molecules21050616. 88. Schneider T, Gries K, Josten M, Wiedemann I, Pelzer S, Labischinski H, et  al. The lipopeptide antibiotic friulimicin B inhibits cell wall biosynthesis through complex formation with bactoprenol phosphate. Antimicrob Agents Chemother. 2009;53:1610–8. https://doi. org/10.1128/AAC.01040-­08. 89. Srinivas N, Jetter P, Ueberbacher BJ, Werneburg M, Zerbe K, Steinmann J, et  al. Peptidomimetic antibiotics target outer-membrane biogenesis in pseudomonas aeruginosa. Science. 2010;327:1010–3. https://doi.org/10.1126/science.1182749. 90. Schultz H, Weiss JP.  The bactericidal/permeability-increasing protein (BPI) in infection and inflammatory disease. Clin Chim Acta. 2007;384:12–23. https://doi.org/10.1016/j. cca.2007.07.005. 91. Menzel L, Orlov D, Wang V, Hong T, Azimov R, Falla T, et al. Bactericidal mechanism of iseganan (IB-367), a rapidly acting antimicrobial protegrin peptide. Interscience conference on Antimicrobial Agents and Chemotherapy. 200;41. https://www.researchgate.net/publication/271217287_Bactericidal_mechanism_of_iseganan_IB-­367_a_rapidly_acting_antimicrobial_protegrin_peptide Accessed 15 Jul 2022. 92. Alam MZ, Wu X, Mascio C, Chesnel L, Hurdle JG. Mode of action and bactericidal properties of surotomycin against growing and nongrowing clostridium difficile. Antimicrob Agents Chemother. 2015;59:5165–70. https://doi.org/10.1128/AAC.01087-­15. 93. Gottler LM, Ramamoorthy A. Structure, membrane orientation, mechanism, and function of pexiganan - a highly potent antimicrobial peptide designed from magainin. Biochim Biophys Acta Biomembr. 2009;1788:1680–6. https://doi.org/10.1016/j.bbamem.2008.10.009. 94. Easton DM, Nijnik A, Mayer ML, Hancock REW.  Potential of immunomodulatory host defense peptides as novel anti-infectives. Trends Biotechnol. 2009;27:582–90. https://doi. org/10.1016/j.tibtech.2009.07.004. 95. Rubinchik E, Dugourd D, Algara T, Pasetka C, Friedland HD.  Antimicrobial and antifungal activities of a novel cationic antimicrobial peptide, omiganan, in experimental skin

Nanocarriers for Delivery of Peptide Antibiotics

33

colonisation models. Int J Antimicrob Agents. 2009;34:457–61. https://doi.org/10.1016/j. ijantimicag.2009.05.003. 96. Crowther GS, Baines SD, Todhunter SL, Freeman J, Chilton CH, Wilcox MH. Evaluation of NVB302 versus vancomycin activity in an in vitro human gut model of Clostridium difficile infection. J Antimicrob Chemother. 2013;68:168–76. https://doi.org/10.1093/jac/dks359. 97. Malanovic N, Leber R, Schmuck M, Kriechbaum M, Cordfunke RA, Drijfhout JW, et  al. Phospholipid-driven differences determine the action of the synthetic antimicrobial peptide OP-145 on gram-positive bacterial and mammalian membrane model systems. Biochim Biophys Acta Biomembr. 2015;1848:2437–47. https://doi.org/10.1016/j. bbamem.2015.07.010. 98. Woong SJ, Xuewei SL, Sun JN, Edgerton M. The P-113 fragment of histatin 5 requires a specific peptide sequence for intracellular translocation in candida albicans, which is independent of cell wall binding. Antimicrob Agents Chemother. 2008;52:497–504. https://doi. org/10.1128/aac.01199-­07. 99. Isaksson J, Brandsdal BO, Engqvist M, Flaten GE, Svendsen JSM, Stensen W. A synthetic antimicrobial peptidomimetic (LTX 109): Stereochemical impact on membrane disruption. J Med Chem. 2011;54:5786–95. https://doi.org/10.1021/jm200450h. 100. Van GR, Kox M, Van ELT, Pickkers P. Immunomodulatory and kidney-protective effects of the human chorionic gonadotropin derivate EA-230. Nephron. 2018;140:148–51. https://doi. org/10.1159/000490772. 101. Kudrimoti M, Curtis A, Azawi S, Worden F, Katz S, Adkins D, et al. Dusquetide: a novel innate defense regulator demonstrating a significant and consistent reduction in the duration of oral mucositis in preclinical data and a randomized, placebo-controlled phase 2a clinical study. J Biotechnol. 2016;239:115–25. https://doi.org/10.1016/j.jbiotec.2016.10.010. 102. Brouwer CP, Welling MM, Brouwer PJM, Roscini CL, Cardinali G, Corte L, et al. Structure-­ activity relationship study of synthetic variants derived from the highly potent human antimicrobial peptide hLF (1-11). Cohesive J Microbiol. Infect Dis. 2018:1. https://doi. org/10.31031/cjmi.2018.01.000512. 103. Guo L, Mclean JS, Yang Y, Eckert R, Kaplan CW, Kyme P, et al. Precision-guided antimicrobial peptide as a targeted modulator of human microbial ecology. Proc Natl Acad Sci U S A. 2015;112:7569–74. https://doi.org/10.1073/pnas.1506207112. 104. Mercer DK, Robertson JC, Miller L, Stewart CS, O’neil DA. NP213 (Novexatin®): a unique therapy candidate for onychomycosis with a differentiated safety and efficacy profile. Med Mycol. 2020;58:1064–72. https://doi.org/10.1093/mmy/myaa015. 105. Fulco P, Wenzel RP. Ramoplanin: a topical lipoglycodepsipeptide antibacterial agent. Expert Rev Anti-Infect Ther. 2006;4:939–45. https://doi.org/10.1586/14787210.4.6.939. 106. Bulger EM, Maier RV, Sperry J, Joshi M, Henry S, Moore FA, et  al. A novel drug for treatment of necrotizing soft-tissue infections: a randomized clinical trial. JAMA Surg. 2014;149:528–36. https://doi.org/10.1001/jamasurg.2013.4841. 107. Muchintala D, Suresh V, Raju D, Sashidhar RB. Synthesis and characterization of cecropin peptide-based silver nanocomposites: its antibacterial activity and mode of action. Mater Sci Eng C Mater Biol Appl. 2020:110. https://doi.org/10.1016/j.msec.2020.110712. 108. Yasir M, Dutta D, Willcox MDP. Mode of action of the antimicrobial peptide Mel4 is independent of Staphylococcus aureus cell membrane permeability. PLoS One. 2019:14. https:// doi.org/10.1371/journal.pone.0215703. 109. Yasir M, Dutta D, Hossain KR, Chen R, Ho KKK, Kuppusamy R, et  al. Mechanism of action of surface immobilized antimicrobial peptides against Pseudomonas aeruginosa. Front Microbiol. 2020:10. https://doi.org/10.3389/fmicb.2019.03053. 110. Leeds JA, Sachdeva M, Mullin S, Dzink-Fox J, LaMarche MJ.  Mechanism of action of and mechanism of reduced susceptibility to the novel anti-Clostridium difficile compound LFF571. Antimicrob Agents Chemother. 2012;56:4463–5. https://doi.org/10.1128/ AAC.06354-­11.

34

B. Karunakaran et al.

111. Travis S, Yap LM, Hawkey C, Warren B, Lazarov M, Fong T, et al. RDP58 is a novel and potentially effective oral therapy for ulcerative colitis. Inflamm Bowel Dis. 2005;11:713–9. https://doi.org/10.1097/01.mib.0000172807.26748.16. 112. Peyrusson F, Butler D, Tulkens PM, Van Bambeke F. Cellular pharmacokinetics and intracellular activity of the novel peptide deformylase inhibitor GSK1322322 against Staphylococcus aureus laboratory and clinical strains with various resistance phenotypes: studies with human THP-1 monocytes and J774 murine macrophages. Antimicrob Agents Chemother. 2015;59:5747–60. https://doi.org/10.1128/aac.00827-­15. 113. Edsfeldt S, Holm B, Mahlapuu M, Reno C, Hart DA, Wiig M, et al. PXL01 in sodium hyaluronate results in increased PRG4 expression: a potential mechanism for anti-adhesion. Ups J Med Sci. 2017;122:28–34. https://doi.org/10.1080/03009734.2016.1230157. 114. Doi K, Hu X, Yuen PST, Leelahavanichkul A, Yasuda H, Kim SM, et al. AP214, an analogue of α-melanocyte-stimulating hormone, ameliorates sepsis-induced acute kidney injury and mortality. Kidney Int. 2008;73:1266–74. https://doi.org/10.1038/ki.2008.97. 115. Mensa B, Howell GL, Scott R, DeGrado WF.  Comparative mechanistic studies of brilacidin, daptomycin, and the antimicrobial peptide LL16. Antimicrob Agents Chemother. 2014;58:5136–45. https://doi.org/10.1128/AAC.02955-­14. 116. Ooi N, Miller K, Hobbs J, Rhys-Williams W, Love W, Chopra I. XF-73, a novel antistaphylococcal membrane-active agent with rapid bactericidal activity. J Antimicrob Chemother. 2009;64:735–40. https://doi.org/10.1093/jac/dkp299. 117. Csato M, Kenderessy AS, Dobozy A. Enhancement of Candida albicans killing activity of separated human epidermal cells by α-melanocyte stimulating hormone. Br J Dermatol. 1989;121:145–7. https://doi.org/10.1111/j.1365-­2133.1989.tb01415.x. 118. Gualillo O, Lago F, Gómez-Reino J, Casanueva FF, Dieguez C. Ghrelin, a widespread hormone: insights into molecular and cellular regulation of its expression and mechanism of action. FEBS Lett. 2003;552:105–9. https://doi.org/10.1016/s0014-­5793(03)00965-­7. 119. Itoh H, Tokumoto K, Kaji T, Paudel A, Panthee S, Hamamoto H, et al. Total synthesis and biological mode of action of WAP-8294A2: a Menaquinone-targeting antibiotic. J Org Chem. 2018;83:6924–35. https://doi.org/10.1021/acs.joc.7b02318. 120. Miyake O, Ochiai A, Hashimoto W, Murata K. Origin and diversity of Alginate Lyases of families PL-5 and PL-7  in Sphingomonas sp. Strain A1. J Bacteriol. 2004;186:2891–6. https://doi.org/10.1128/JB.186.9.2891-­2896.2004. 121. Yu HB, Kielczewska A, Rozek A, Takenaka S, Li Y, Thorson L, et  al. Sequestosome-1/ p62 is the key intracellular target of innate defense regulator peptide. J Biol Chem. 2009;284:36007–11. https://doi.org/10.1074/jbc.c109.073627.

Nanomedicines for the Pulmonary Delivery of Antibiotics Arnab Ghosh and Rohit Srivastava

Abstract  The pulmonary delivery of antibiotics is a pivotal approach in treating respiratory infections, enabling targeted drug administration while minimizing systemic side effects. In recent years, nanomedicine-based strategies have emerged as promising means to enhance the efficacy and specificity of antibiotic delivery to the lungs. Nanoparticulate carriers offer unique properties such as controlled release, improved stability, and enhanced targeting within the complex respiratory system. This comprehensive chapter thoroughly examines the multifaceted aspects of nanomedicines for pulmonary antibiotic delivery, encompassing particle deposition mechanisms, factors influencing efficacy, clinical indications, and regulatory considerations. The emergence of multidrug-resistant (MDR) strains poses a significant challenge in respiratory infections, warranting the development of innovative approaches to combat these pathogens. Nanomedicines present an opportunity to overcome MDR by enabling the targeted and effective delivery of antibiotics to the lungs. While there are hurdles to address, including translation to clinical practice and regulatory frameworks, ongoing research and technological advancements hold great promise for the future of nanomedicine-based pulmonary antibiotic therapy. In the context of respiratory infections, the COVID-19 pandemic has underscored the need for novel approaches to respiratory drug delivery. Nanomedicines have shown potential in COVID-19 management by facilitating targeted delivery of antimicrobial agents, including antibiotics, and antiviral agents to the lungs. Aerosolized nanomedicines offer advantages such as improved bioavailability, extended retention in the respiratory tract, and potential synergistic effects when combined with antiviral therapies. Furthermore, the ability of nanocarriers to modulate immune responses and mitigate excessive inflammation may prove instrumental in managing the severe respiratory complications associated with COVID-19. As research in this area continues, nanomedicine-based pulmonary delivery holds promises for enhancing the effectiveness of antibiotic therapy in A. Ghosh · R. Srivastava (*) NanoBios Lab, Indian Institute of Technology, Bombay, Bombay, India

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 V. B. Patravale et al. (eds.), Nanomedicines for the Prevention and Treatment of Infectious Diseases, AAPS Advances in the Pharmaceutical Sciences Series 56, https://doi.org/10.1007/978-3-031-39020-3_2

35

36

A. Ghosh and R. Srivastava

­ ARS-CoV-2-­infected patients and improving clinical outcomes in COVID-19 S respiratory manifestations. However, further investigations and clinical trials are warranted to fully elucidate the potential of nanomedicines in this critical aspect of this pandemic management. In conclusion, this comprehensive chapter highlights the significant potential of nanomedicines in the pulmonary delivery of antibiotics for respiratory infections. By leveraging the unique properties of nanocarriers, such as controlled release, and enhanced targeting, nanomedicine-based approaches offer the possibility of improving drug efficacy while minimizing systemic side effects. Furthermore, the challenges with the management of MDR strains and SARS-CoV-2 emphasize the importance of exploring nanomedicine-based solutions. Continued research and clinical investigations are essential to unlock the full potential of nanomedicines for personalized and effective treatment modalities in respiratory medicine and also for addressing the global challenges of antimicrobial resistance. Keywords  Nanomedicines · Pulmonary delivery · Antibiotics · Respiratory infections · Multidrug-resistant strains · Aerosolized antibiotics · Drug targeting · Antimicrobial resistance · Nebulized antibiotics · Inhaler Antimivrobials · Nanoantibiotics · Aerosolized Antibiotics

Abbreviations AAPS American society of Pharmaceutical Scientists AIDS Acquired immune deficiency syndrome API active pharmaceutical ingredients AS aerosolized ASD advanced spray drying ATS American Thoracic Society BC Before Christ BID Brownian diffusion CBA colistin base activity CD concentration-dependent CF Cystic fibrosis CNDP Critical nanoscale design parameters COPD chronic obstructive pulmonary disease COVID coronavirus disease CPIS clinical pulmonary infection score DDS drug delivery systems DLPC 1,2-dilauroyl-sn-glycerol-3-phosphocholine DNA Deoxyribonucleic acid DPI dry powder inhaler DSC Differential Scanning Calorimetry EC Expiratory Capacity

Nanomedicines for the Pulmonary Delivery of Antibiotics

37

EDR extended drug-resistant ERV Expiratory Reserve Volume ESCMID European Society of Clinical Microbiology and Infectious Diseases FDA Food and Drug Administration FICS French Intensive Care Society FRC Functional Residual Capacity FSAICM The French Society of Anaesthesia and Intensive Care Medicine GNB gram-negative bacilli HAP hospital-acquired pneumonia HFA hydrofluoroalkane HIV Human Immunodeficiency Virus HPH high-pressure homogenization IC Inspiratory Capacity ICU intensive care units IDSA Infectious Disease Society of America IM Inhaled mass IM intramuscular IPN inverse phase nanoprecipitation IRV Inspiratory Reserve Volume ISO International organization for standardization IUBMB International union of Biochemistry and Molecular Biology IV intravenous JAMA Journal of American Medical Association LD loading dose LN liposomal nanostructures MAC mycobacterium avium complex MDI metered dose inhaler MDR multidrug-resistant MERS Middle East Respiratory Syndrome MIU million international units MMAD Mass median aerodynamic diameter MPEG methoxy poly (ethylene glycol) MV mechanical ventilation NP Nanoparticle PA Pseudomonas aeruginosa PDDS Pharmacokinetics and lung delivery PEG polyethylene glycol PFT pulmonary function tests PLGA Poly(d,l-lactide-co-glycolide) acid PM Particle mass Pmdi pressurized metered dose inhaler PN Polymeric nanoparticles Ppl Negative pleural pressure PRINT particle replication in a nonwetting template PSD particle size distribution

38

PSD Ptp RCT RF RM RNA RV SARS SFD SFE SIMANIM SLN SMI Stk TLC TMNP TV VAP VAT VC XDR

A. Ghosh and R. Srivastava

particle size distribution transpulmonary pressure randomized control trial Respirable fraction Respirable mass Ribonucleic acid Residual Volume Severe acute respiratory infection spray freeze-drying supercritical fluid (antisolvent) extraction simultaneously manufactured nano-in-micro solid-lipid nanoparticle slow mist inhaler Stokes’ number Total Lung Capacity Trojan Micronano Particles Tidal Volume ventilator-associated pneumonia ventilator-associated tracheobronchitis Vital Capacity extended drug-resistant

1 Introduction The first known reference to therapeutic aerosol delivery was documented in ancient Egypt on a ∼1554  BC papyrus scroll (Ebers papyrus) discovered at the ‘Theban necropolis’ of Assassif district, between the legs of a mummy [1]. Technological advances in manufacturing, however, beginning with the industrial revolution, allowed for the mass production of medicinal aerosol delivery devices and peaked speed in the twenty-first century. With more knowledge about the pulmonary tree as a drug delivery site with its many advantages and challenges, the advent of nanomedicine for pulmonary applications has emerged as a great area of research with translational potential. The ongoing global Covid pandemic, which irked many questions on healthcare delivery systems practicing conventional mode of drug delivery, has routed researchers to relook at the respiratory system as a route for local as well as systemic delivery of active pharmaceutical ingredients (APIs) [2], for instance, vaccines, steroids, antivirals, bronchodilators, mucolytics, and many others.

Nanomedicines for the Pulmonary Delivery of Antibiotics

39

1.1 Lungs as Delivery Sites The large surface area of the lungs, bypassing of fast pass metabolism, and high vascularity [3] are advantages of the pulmonary route of API administration. However, there are certain limitations due to the complexity and typicality of the respiratory tract. In most cases, clinical profiles, rather than cell culture results, are more relevant in determining efficacy and adverse reactions of the APIs. The finest terminal airways (unciliated) and alveoli play crucial roles in particle exchange across the blood-gas barrier. Therefore, the pulmonary delivery of the nanoforms of the APIs, especially the antimicrobials, is a promising field of fundamental, clinical, and translational research.

1.2 Epidemiology of Pulmonary Infections The epidemiology of respiratory diseases demonstrates a worldwide huge burden [4] of acute and chronic lung diseases across all demographic regions. Due to exposure to the external atmosphere, the respiratory system is prone to various infections, chiefly through aerosol exposure. Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus sp., Streptococcus sp., Aspergillus sp., coronavirus, respiratory syncytial virus, and influenza virus are a few examples of common human respiratory pathogens [5].

1.3 Chronic Lung Conditions as a Nidus of Infections Most chronic respiratory diseases are incurable and become nidus of various infections, such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, interstitial lung disease, and many more. In most cases, they are manageable with regular follow-ups. Mortality increases significantly with superimposed infections.

1.4 Opportunistic Lung Infections Besides, opportunistic lung infections like tuberculosis (endemic in many countries as well), Pneumocystis jirovecii, Mycobacterium avium complex (MAC) and many others in immuno-compromised hosts [6] like in HIV/AIDS or transplant recipients increase the mortality significantly.

40

A. Ghosh and R. Srivastava

1.5 Long COVID After the global pandemic of SARS-CoV-2 since 2019, there have been increased incidences of complications like persistent dyspnea, long-term oxygen dependence, ventilator dependence, abnormal pulmonary function tests (PFTs), and lung fibrosis [7, 8]. The effects of long Covid on premorbid conditions and resultant infections are unknown and are expected to increase the global burden of lung infections in coming years.

1.6 Nanomedicine APIs Nanomedicine is the application of nanomaterials with a size range of 1–100 nanometres [9] in medical and other healthcare-related fields for diagnosing, controlling, preventing, and treating diseases. The small size of nanomaterials being close to many biomolecules makes them extremely effective for many in vivo and in vitro biomedical research and applications. Various nanoforms, for example, polymers, liposomes, micelles, antibodies, and others, have been extensively studied in the last few decades. In addition to therapeutic applications, nanomedicine formulations have recently been used for imaging purposes [9]. Polymeric nanoparticles (PN), solid-lipid nanoparticles (SLN), and liposomes have also been studied to treat various pulmonary diseases.

1.7 Nano-DDS and Multidrug-Resistant Strains Inhaled nanotechnology-based drug delivery systems (nano-DDS) hold promises in all these scenarios and especially for tackling multidrug-resistant (MDR) or extended drug-resistant (XDR) strains and superbugs. It has been achieved in recent years through antibiotic encapsulation into nanoparticle carriers. The current encapsulated inhaled antibiotic formulations, for example, the cationic aminoglycoside tobramycin for P. aeruginosa biofilm that deliver the free forms of the antibiotics, have increased antibiotic exposure in the infected lung. Antimicrobial retention time is increased by bypassing the immune system cells in the lung bed with nanoparticulate drugs.

1.8 Nano-Periodic Property and Critical Nanoscale Design Parameters Critical nanoscale design parameters (CNDP) [10] such as particle size, shape, surface chemistry, flexibility/rigidity, architecture, and elemental composition, can be used to control and engineer particles to optimize pharmacokinetics,

Nanomedicines for the Pulmonary Delivery of Antibiotics

41

pharmacodynamics, and site-specific disease targeting and thus constitute what Kannan et al. call a ‘nano-periodic property’ [11] describing the correlation between nanoparticle activity and in vivo behaviors. The use of nanotechnology is currently reshaping the pharmaceutical industry, most notably in inhalation medication delivery. Medications can be inhaled using dry powders like nanoparticles, as mentioned in this research. Even though airways and lung beds provide a promising drug delivery route for local and systemic effects, mucus barriers, diffusion barriers, emphysema, airway obstructions, and structural and functional lung diseases significantly alter the efficacies of the inhaled drugs. Only a few formulations, for instance, the liposomal nanostructures (LN), are commercially available for pulmonary administration. The micelles and PNs have been studied extensively, though.

1.9 Mode of Delivery of Inhaled Antimicrobial APIs Inhaled/aerosolized antimicrobial APIs directly given through the respiratory tract is gaining popularity due to less potential toxicity and more targeted effects. The primary mode for aerosolized pulmonary delivery of anti-infective agents is via nebulization, the most common type of which is the jet nebulizer. The other nebulizer uses ultrasonic mesh, requires less power to run, and is more portable and ergonomic.

1.10 Aim of This Book Chapter The title of this book chapter highlights the understanding of the respiratory system in health and diseases, mechanics of inhalation drug delivery and modes, nano forms of targeted respiratory antimicrobials, the epidemiology, clinical profiles, and treatment modalities of respiratory infections with the combination of the above and the translational potential and challenges related to the development of such delivery systems. Each of the above considerations is relevant for a clear understanding of the disposition of nanoform API antimicrobials for the treatment or prevention of various infections. Challenges, limitations, and future goals have been projected.

2 Anatomy and Physiology of the Respiratory System The lungs and other structural organs that make up the human respiratory system are principally in charge of exchanging gases. The process by which carbon dioxide (CO2) produced by the cells is exchanged for oxygen (O2) from the atmosphere is known as respiration. The right and left lungs have three and two lobes, respectively. An adult human has about 300 million alveoli, corresponding to about 80 square

42

A. Ghosh and R. Srivastava

meters of surface area for gaseous exchange [12]. Air passes during inspiration through the upper respiratory tract consisting of nostrils, nasal cavity, nasopharynx, oropharynx, hypopharynx, epiglottis, vocal cords and then through conducting zone comprising of the trachea, bronchi (right and left), and smaller air passages like terminal bronchioles. Then it passes through the respiratory bronchioles (transition zone), alveolar ducts-alveolar sacs-alveoli (respiratory zone), respectively. The alveoli, blood vessels, and lymph tissue comprise the lung bed. The bronchi are subdivided further into primary and secondary bronchi, bronchioles, and alveoli. The blood-gas barrier comprises of the pulmonary capillaries that line each alveolus, creating a massive network with more than 280 billion capillaries and a surface area of nearly 80 m2. Figure 1a–c below describes the broad division of respiratory tract division of the airways and the gas exchange mechanism across the blood-gas barrier, respectively. The interface between alveolar epithelium, endothelium, and interstitial cell layers is where alveolar gas exchange occurs mostly. The alveolar wall comprises of Type I and Type II epithelial cells (pneumonocytes). There is only one endothelial layer between the capillaries and the alveolar epithelium. Diffusion at the blood-gas interface promotes gas exchange because of the extreme thinness of the interface and the proximity between alveoli and capillaries (about 0.5  m) [13]. Alveolar fluids and mucus, primarily composed of phospholipids and surface proteins, cover the alveoli. A thin layer of connective tissue supports these distal respiratory passages. This layer comprises of lymphatic vessels, nerves, macrophages, and fibroblasts [13]. Given that it has access to the lymphatic and pulmonary systems, this area is excellent for administering medications. The lung volumes can be measured by pulmonary function test (PFT), as mentioned in Table 1. Figure 2 shows a graphical representation of various lung volumes and capacities.

2.1 Physiology of Gas and Particle Exchange A concentration gradient is responsible for the majority of gas exchange during respiration. The thickness of the membrane and the gas solubility primarily determine the diffusion rate. Oxygen and Carbon dioxide diffuse along their respective pressure gradients and move independently. In a healthy lung, oxygen from the air within the alveoli diffuses into the blood capillaries, while CO2 is expelled from tissue cells and into capillaries due to the pressure gradient. Negative pleural pressure (Ppl) is sufficient during the inspiratory phase to expand the lungs. The following equation can be used to calculate transpulmonary pressure (Ptp), also known as distending pressure, which can be derived from the equation [14]:

Ptp  Paw  Ppl ,



where Ptp, Paw, and Ppl are transpulmonary, alveolar, and Pleural pressure, respectively.

Nanomedicines for the Pulmonary Delivery of Antibiotics

43

Fig. 1 (a) Gross Anatomy of Respiratory System. (b) Lungs and the upper respiratory tract. (c) Alveolar structure and blood-gas barrier where oxygen is diffused in, and carbondioxide is diffused out. Oxygenated blood goes to the left atrium of the heart through pulmonary veins. Deoxygenated blood is carried through the pulmonary arteries and comes to alveolar space and is further exhaled during expiration. Typically, the blood-gas barrier is less than 0.5 micron thick

2.2 The Blood-Gas Barrier According to Fick’s law of diffusion [15], the amount of gas diffusing across the barrier is proportional to its area and inversely proportional to its thickness. The bloodgas barrier consists of the capillary endothelium, the extracellular matrix, and the alveolar epithelium. The interface is extraordinarily thin (Fig. 1c inset) but is remarkably strong. The epithelial type II cells secrete pulmonary surfactants, a mixture of lipids and proteins. These are highly enriched in dipalmitoyl-­phosphatidylcholine and two closely connected bilayer lipid/protein structures [16].

44

A. Ghosh and R. Srivastava

Table 1  Definitions of Different Lung Volumes Lung volumes Tidal volume (TV) Inspiratory reserve volume (IRV) Expiratory reserve volume (ERV) Residual volume (RV) Inspiratory capacity (IC) Expiratory capacity (EC) Functional residual capacity (FRC) Vital capacity (VC)

Total lung capacity (TLC)

Definition the volume of air that passes through or leaves the lungs per respiratory cycle. In a healthy person, it is approximately 500 mL. after regular inspiration, the additional air volume can be maximally inspired between 2500 and 3000 mL on average. after a typical expiration, the additional air volume can be expelled to its maximum capacity. This typically contains 1000–1100 mL. the amount of air in the lungs that is still present after fully exhaling. This typically contains 1200 mL. the most air that can be inhaled following a typical expiration. It is the result of IRV and TV combined. the maximum amount of air that can be exhaled following a typical inspiration. It is the result of adding ERV and TV. the quantity of air in the lungs after a typical expiration. RV and ERV are included in this. the maximum amount that can be exhaled or the maximum amount that can be inhaled after the maximum inspiration. TV, ERV, and IRV are included in this. the total volume of the lungs when fully expanded or the air they can hold after taking a deep breath. This includes TV, ERV, IRV, RV, and VC + RV.

Fig. 2  Pictorial depiction of various lung volumes and capacities

Nanomedicines for the Pulmonary Delivery of Antibiotics

45

2.3 Diffusion in Diseased Lungs In a diseased lung bed, however, gas exchange efficiency is compromised for several reasons, including inflammation, scarring, and aberrant cells. For instance, inflammation and scarring in the airways can cause them to become constricted, as seen in chronic obstructive pulmonary disease (COPD) and asthma [17]. This makes it more difficult for air to enter and exit the lungs, resulting in impaired gas exchange, shortness of breath, and difficulty breathing. The flexibility of the airways and alveoli and a person’s overall health determine effective gas exchange. In addition to gas exchange, the lungs perform various secondary functions, such as filtering pollutants from inhaled air. Small hair-like structures called cilia and mucus produced by respiratory tract cells work to catch and remove airborne particles before they reach the alveoli in a healthy lung bed. However, a diseased lung bed cannot filter out particles efficiently, increasing the risk of respiratory infection and other disorders. Resistance to airflow, which is primarily brought on by airway inflammation, limits airflow in sick lungs. Several factors like the airway size, airway structure, breathing pattern (flow and volume), route of breathing (nose vs. mouth), and inhaled particle size, can influence particle entry to the respiratory bed. In healthy lungs, the peripheral lung units expand to fill the entire lung, causing even ventilation. However, the small bronchioles may collapse or become tethered in the diseased lung due to increased tissue tension. This disturbs the delicate balance of tissue tensions and minimizes flow resistance for exchanging gases effectively. In diseases such as emphysema, the coarse fiber system is destroyed, which reduces laminar flow and causes many gas exchange-units to be affected. It can also affect airflow distribution within parallel airway tracts by widening them during inspiration, thus altering their size. This can result in a differential airflow distribution, affecting its velocity, residence time, and gas exchange efficiency.

3 Factors Influencing Nanoparticulate Antimicrobial Delivery Compared to the traditional oral route, inhalation therapy for drug delivery has several benefits, including a quick onset of action, self-administration, noninvasive, target-specific, and minimal drug degradation [18–20]. Particle size is crucial for reaching the nano-antibiotic particles in the desired airways.

3.1 Effect of Particle Size The size of the particles in a nanoparticulate antimicrobial drug can significantly impact its ability to be administered via inhalation. Due to the small size, nanoparticulate drugs can more effectively reach and stay longer at the alveoli level [21]. A

46

A. Ghosh and R. Srivastava

narrow and controlled ‘particle size distribution’ (PSD) is critical for improving and delivering consistent aerodynamic performance for the aerosolized antibiotics nanoforms. Since, in general principles, particles with a diameter between 1 and 5 microns tend to accumulate in the lungs [22], nanoforms serve the purpose efficiently.

3.2 Reduction Methods Various particle size-reduction and particle-engineering techniques, such as air jet milling, spray drying, and wet polishing, are widely used to produce an aerodynamically suitable size range [22].

3.3 Deposition Versus Stability The size of the nanomedicine favors drug deposition in the lung and, consequently, systemic delivery, while the zeta potential aids in the management of system stability [23].

3.4 Formulations In general, drugs formulated as fine powders or mists are more likely to deliver smaller particles and may be more effective for administration through the inhalation route. Also, inhaler devices are more likely to produce smaller particles that emit a fine mist or utilize a high-pressure system to deliver the drug.

4 Mechanics of Deposition of Nanoparticle Antimicrobials Though nanoparticle size is in the nanoscale, they form aggregates in the micrometer ranges, and thus the most suitable mechanism of drug deposition is sedimentation. Besides the dimensions, morphology, geometrical orientation, surface activities, mass, the particle size of aerosols, breathing frequencies, the humidity of inspired air, flow velocity, and tidal volume are important factors for drug deposition in nanoscale systems [24]. The three most important delivery mechanisms through inhalation are impaction, sedimentation, and diffusion.

Nanomedicines for the Pulmonary Delivery of Antibiotics

47

4.1 Impaction Larger particles (those with a diameter greater than 5 μm) are more susceptible to inertial impaction, which occurs when a gas flow’s direction abruptly changes, as it does in the upper airway and at airway bifurcations. The particle’s chance of deposition on an airway wall increases as the particle’s mass and flow rate increase. This probability is expressed as a function of the Stokes’ number (Stk), defined by:





Stoke’s Number  24  : Stk    d 2 u / 18  d  ;



where dρ is the particle diameter, ρρ is the density, u is the mean velocity, and μ is the dynamic viscosity of the carrier gas. Particles are more likely to settle into place by inertial impaction at higher Stokes’ numbers [25]

4.2 Gravitational Sedimentation For particle sizes between 1 and 5 μm, gravitational deposition, called sedimentation, is another mechanism for drug delivery in the smaller airways and bronchioles. More deposition is observed if settling time is more, for instance, slow and deep breathing. Particles’ terminal settling velocity (Vs) can be calculated from the equation given below:





Vs    d 2  g / 18  ;



where dρ is the particle diameter, ρρ is the density, μ is the dynamic viscosity of the carrier gas, and g is the gravitational constant. Particles between 1 and 8 μm in size benefit most from this deposition process, whereas particles of bigger and smaller sizes deposit by inertial impaction and Brownian diffusion.

4.3 Deposition by Brownian Diffusion (BD) Yet another important thing in drug deposition is the ‘Brownian diffusion (BD)’ of particles after they come in contact with the pulmonary surfactant and gas molecules, especially in the acinar region (low air-velocity areas). Unlike impaction and sedimentation, BD is effective for particle size less than 0.5 μm and B. diffusion coefficient DB. can be calculated by equation [26]:

DB   ckT  / 3 d



48

A. Ghosh and R. Srivastava

where to account for the reduced air resistance due to slippage as the particle diameter approaches the mean free path of the gas molecules, we use the expression: where k is Boltzmann’s constant [27], T is the absolute temperature, dρ is the particle diameter, and c is the Cunningham’s correction factor [26].

4.4 Turbulent Mixing As a result of the turbulent regime’s unpredictable fluctuations or mixing, the trajectories of particles continually alter in size and direction before deposition on the walls of the airways. The average flow affects inertial impaction deposits, whereas variabilities influence turbulent mixing deposits in the flow.

4.5 Interception Interception is the process by which particles, while following the main flow, make contact with an airway wall due to their size and form. Although minor for spherical particles, this is the most important process for fibers and other elongated particles.

4.6 Electrostatic Precipitation Electrically charged particles near the surfaces of airways create surface image charges. Charged particles are, therefore, electrostatically attracted to the airway walls, which may result in a larger deposition of charged particles than neutral particles. The mechanism of deposition of particles of varying sizes, their own, and the airways is pictorially represented in Fig. 3.

5 Factors Affecting the Efficacy of Aerosolized Nanoantibiotics Though the size of particles matters a lot in targeted delivery to the distal airways, certain other factors bring drastic changes in the treatment outcomes. A few of these key factors are mentioned below in Table 2:

Nanomedicines for the Pulmonary Delivery of Antibiotics

49

Mechanism of Particle Deposition As per Size of the Particles

Impaction

Sedimentation Sedimentation

Brownian motion

Size Range max ( in micron)

Size Range min ( in micron)

Alveoli

Bronchioles

Secondary Bronchi

Primary Bronchi

0

2

4

6

8

10

12

Fig. 3  Mechanism of particle deposition as per size of particles

6 Etiologies of Respiratory Infections Respiratory tract infections are the leading cause of global morbidity and mortality [38]. Almost all microorganisms, including viruses, fungi, and bacteria, can interfere with the respiratory system’s normal physiology and cause inflammation and other conditions. A “biological war” between the factors determining a pathogen’s pathogenicity and the early host defense occurs when these pathogens can infect people despite these defenses [18, 39]. Before triggering an immune response, a pathogen must pass several basic respiratory defenses. The immune system is key to how respiratory infections develop and spread. The immune system can find and get rid of pathogens, which sends out immune cells and substances like antibodies and cytokines. When a person has a respiratory infection, the immune system may cause inflammation to eliminate the pathogen and protect the body. But this inflammation can also cause things like trouble breathing and edema at the inflamed site. Overall, the pathophysiology of respiratory infections is a complicated set of interactions between the pathogen, the immune system of the host, and changes in normal body functions caused by the infection. Table 3 lists the most common respiratory infections, symptoms, and causative agents, and Table 4 mentions the organisms causing pneumonia.

50

A. Ghosh and R. Srivastava

Table 2  Factors affecting antibiotics aerosol delivery through nebulizers Factors Physical properties

Subfactor Particle mass (PM)

Inhaled mass (IM)

Respirable mass (RM)

Mass median aerodynamic diameter (MMAD)

Environmental variables

Surface tension Aerodynamics And Cascade impactors (Cis)

Drug solubility

Definition/Effects The percentage of the nominal dose (PM) expelled from the inhaler measures how effective the device is [28]. The resistance of the nebulizer air circuit and compressor output must be optimized for maximal mass output. Nebulizer-­ compressor output data from the manufacturer is usually of the compressor itself without the nebulizer connected. Hence, there are wide variations in nebulizer outputs across different models. Ultrasonic/mesh devices have better mass output than jet ones. IM denotes the percentage of a nebulizer’s charge that a patient inhales. There is no one set of criteria that can be used to evaluate the quality of a nebulizer or its therapeutic efficacy [29] The RM, or fine particle fraction, refers to the proportion of the inhaled mass that consists of particles small enough to pass through the upper airways and settle in the lower airways (usually an aerodynamic diameter between 1 and 5 μm) [30]. For particles with a given mass, the mass median aerodynamic diameter is the diameter at which half of the particles in the aerodynamic size distribution fall. Particles are deposited in the airway by inertial impaction and sedimentation, whereas particles of a smaller size deposit via diffusion [18]. In most cases, environmental conditions like humidity, temperature, density, and viscosity (aqueous solution or suspension) play a major role in the delivery of nebulized antimicrobial drug doses. The presence of other medicines, surfactants, and solvents affects the surface tension of antimicrobial aerosols. Sometimes, the physical diameter of the NPs might differ significantly from the aerodynamic one. Therefore, the evaluation of physical size is insufficient in terms of inhaling administration. This calls for multistage CIs in any novel formulation created for this purpose [31]. The particle diffusion diameter should be used in place of the aerodynamic diameter for particles with an aerodynamic diameter of less than 0.5 μm. Greater solubility correlates with smaller particles that can remain suspended for longer [32]. (continued)

Nanomedicines for the Pulmonary Delivery of Antibiotics

51

Table 2 (continued) Factors Device Related Parameters

Device and inspiratory efforts Particle Related Parameters

Subfactor Nebulization output/output rate

Definition/Effects The nebulization rate affects antibiotic effectiveness. The particle size/mass and distributions are important factors. A higher flow results in a higher output rate and a central deposition [33]. A jet nebulizer, however, is limited by the ideal inspiratory flow rate ranging between 15 and 30 liters per min [34]. Atomized particle Devices that produce smaller particles are more likely to size produce a higher respirable fraction and deposit the antibiotic deep into the alveoli. Lung dose The lung dosage is the quantity of medication that reaches the airways (i.e., crosses the voice cords), is absorbed by the lungs, and is expressed in percentage of particle/inhaled mass. The optimal dosage for a given drug depends on the specific drug, the patient’s condition, and the response to the treatment [35]. A healthcare provider should be consulted to determine the appropriate dosage for a given patient. Delivery Devices with a higher delivery efficiency are more likely to efficiency deliver a higher drug dose to the deep lung [36]. Flow rate Flow rate can impact the efficacy of nebulized/atomized drugs by affecting the size of the drug particles and the time they remain suspended in the air [37]. Optimal flow rate depends on the drug, device, and the patient’s breathing pattern. Inhalable When the inhalable fraction (mentioned below) is to be convention measured, sampling devices must meet a certain target specification. Inhalable fraction The mass percent of total airborne particles breathed by the nose and mouth. It is determined by the speed and direction of airflow, breathing rate, and other elements (Ref: ISO 7708). Respirable The proportion of inhaled particles that reach a person’s fraction (RF) airways (unciliated region). Higher RF means better reach to distal airways. Larger-sized particles have less RF than nano-formulations (Ref: ISO 7708). Deposition Smaller particles are more likely to deposit in the deep lung, while larger particles may deposit in the upper airway. The proportion of inhaled particles that do not pass through Extra thoracic fraction the larynx(Ref: ISO 7708). Thoracic fraction The proportion of inhaled particles pass through the larynx (Ref: ISO 7708). Misc Thoracic convention: Target specification for sampling (Ref: ISO 7708) instruments when the thoracic fraction is of interest. Tracheobronchial fraction: Mass fraction of inhaled particles that penetrate beyond the larynx but fail to penetrate the unciliated airways. Tracheobronchial convention: Target specification for sampling instruments when the tracheobronchial fraction is interesting. (continued)

52

A. Ghosh and R. Srivastava

Table 2 (continued) Factors Output and output rate

Clinical

Subfactor Peripheral lung deposition

Definition/Effects Increasing the nebulizing flow causes a narrower particle size distribution (MMAD) and a greater respirable percentage, which may enhance peripheral lung deposition. Methods of output Methods include weighing a nebulizer, measuring the measurements change in osmolarity or concentration before and after nebulization, or directly measuring the aerosols. Solvent and Evaporation of the solvent may increase drug concentration. output rate Volume vs. mass Nebulizer output is better expressed in mg/min rather than per min ml/min because the solvent’s evaporation can give false concentrations results. Duration The optimal treatment duration for a given drug depends on the specific drug, the patient’s condition, and the response to the treatment. Longer duration of nebulization pertains to long drug exposure time and adverse effects [35].

Table 3  Common respiratory diseases and their clinical features Disease Common cold

Symptoms Sneezing, runny nose, sore throat, cough

Bronchitis

Sore throat, chest discomfort, production of mucus, fatigue Chest pain, fever, chills, loss of appetite, shortness of breath Fever, muscle aches, dry cough, sore throat

Pneumonia Influenza Laryngitis

Hoarseness, loss of voice, congestion or runny nose, fever Pertussis Initial symptoms: Mild fever, cough, nasal (whooping cough) congestion, Late Symptoms: Vomiting, whooping sound while inhalation, repeated coughing Tuberculosis Fever, loss of appetite, chest pain, shortness of breath, weight loss, cough with mucus or blood

Causative Organism Rhinoviruses (most common), adenoviruses Influenza virus, adenovirus, rhinovirus Streptococcus pneumoniae, Mycoplasma pneumoniae Influenza viruses, RNA viruses Viral pathogens, bacterial pathogens Bordetella pertussis

Mycobacterium tuberculosis

7 Characteristics of Inhaled NP Antibiotics Inhaled antimicrobials have been successfully tried on cystic fibrosis (CF) bronchiectasis. Broadly the clinical indications can be divided into CF and Non-CF applications. In CF with chronic Pseudomonas aeruginosa (PA) infection, inhaled antibiotics, for example, colistin, tobramycin, aztreonam lysine, and levofloxacin, as maintenance therapy, have been successfully tried. In addition, these antimicrobial NP.s are utilized to prevent acute pulmonary exacerbations in patients with CF NP formulations of antibiotics for inhaled route claim to reduce dose-related side effects due to prolonged retention at the target location and reduced systemic

Nanomedicines for the Pulmonary Delivery of Antibiotics

53

Table 4  Etiological agents for pneumonia Type of Organisms Causative Organisms Bacterial Streptococcus sp. Staphylococcus aureus Haemophilus influenzae (type b) Klebsiella Pseudomonas aeruginosa Mycoplasma pneumoniae Legionella pneumophyla Chlamydophila pneumoniae Chlamydophila psittaci Chlamydia trachomatis Coxiella burnetii Viral Influenza virus A, coronavirus pneumonia, (SARS-Cov-1 and 2 pneumonia), Parainfluenza virus 1, 2, 3, Respiratory syncytial virus, Adenovirus 1–7, 14, 21, Middle East Respiratory Syndrome (MERS), Epstein-Barr virus, Coxsackie A virus, Cytomegalovirus Fungal Aspergillus spp. Coccidioides immitis Histoplasma capsulatum Pneumocystis jirovecii Blastomyces brasiliensis Candida spp. Cryptococcus neoformans

Remarks Typical

Atypical

Chiefly atypical

Chiefly atypical

exposure. Nanodelivery technologies can alter the physical and chemical properties of traditional antibiotics to target them in the right place. Recently, smart nanobased drug delivery systems have been developed to precisely target the intended location and release medications under particular stimuli, increasing local drug concentrations and reducing side effects in healthy areas [40]. Lung infection microenvironment studies have been conducted. Respiratory pathogenic bacteria can cause airway inflammation, reduced pH, and elevation in enzyme and reactive oxygen species (ROS) levels [41]. All of these aberrant indicators can stimulate smart nanosystems to release medicines.

7.1 Nanoparticle (NP)-Based Antibiotics: The CF-PA Tobramycin (Tbm) Model Unencapsulated Tbm (aminoglycoside) cannot penetrate the thick DNA-rich mucus in CF lungs, limiting antibiotic exposure to indigenous bacteria. A study by Jill Deacon et al. [42] on polymeric NP of Tobramycin on PA infection in a CF mode

54

A. Ghosh and R. Srivastava

Fig. 4  Conventional tobramycin antibiotic in PA infection. The mucus barrier is inhibiting drug efficacy. Bacterial inhibition is not achieved and drug is cleared rapidly

Fig. 5  Nanoparticulate tobramycin with DNAse enzyme, which disrupts mucus plug and release the free antibiotic in the infection bed. Bacterial inhibition is significantly achieved, and residual drug is present

showed that the conventional Tbm had rapid clearance in the presence of a mucus barrier (Fig. 4) [42]. NP-Tbm could overcome the mucus barrier and achieve higher local concentrations and residual drug effects with a significant reduction in bacterial load (Fig. 5).

7.2 Advantages Drug delivery to the lungs through inhalation has advantages, such as the rapid onset of action, which further enhances bioavailability. Due to the large surface area of airways, absorption is better, and drug wastage is less. Patients can self-­administer

Nanomedicines for the Pulmonary Delivery of Antibiotics

55

the drugs noninvasively [3]. This improves compliance. Drugs are degraded or metabolized in small fractions due to multiple bypasses like gastric acid, fast pass metabolism, presence of food in oral delivery methods. High solute permeability [3] also improves systemic absorption through the pulmonary route. Retention ability is significantly prolonged within the lungs. Nanocarrier prevents antibiotics from chemical or enzyme degradation, such as beta-lactamases. To achieve targeted delivery, there is a possible chance to formulate nanomedicine with properties of mucoadhesive nature by adding various molecules.

7.3 Challenges to Making Dry Powder NPs Aggregations, hygroscopicity, and maintenance of the active principles of the NPs are the main challenges apart from the re-dispersion issues in the respiratory secretions and mucus. After reaching the lung, particles must pass the air-blood barrier. Protease enzymes destroy proteins, whereas smaller chemicals are removed swiftly from the lungs. The process of making the NPs is aimed at preserving the therapeutic potential intact. Surface engineering of the NPs is the key to overcoming the same.

7.4 Methods of NP Preparation: Examples There are various methods for NP antibiotics preparation. A few mentions are high-­ pressure homogenization (HPH), milling, spray freeze-drying (SFD), advanced spray drying (ASD), inverse phase nanoprecipitation (IPN), particle replication in a nonwetting template (PRINT), supercritical fluid (antisolvent) extraction (SFE), thermal condensation and controlled aerosol growth.

7.5 Modifications in NPs for Better Functions The aerodynamic diameter of the particles is reduced by increasing the porosity and hollowness in the particles and thus having low-density particles, increasing dynamic shape and decreasing the dV, which is the volume equivalent diameter of particles [43]. The dispersion is improved by decreasing surface energy, making ‘Trojan Micronano Particles’ (TMNPs), and incorporating effervescence. Particles can be protected from mucus and intermediate destruction or degradation by polymer or lipid coatings [43]. Various modifications of NPs are mentioned in Table 5. Types of NPs coating: Fig. 7a–e shows various nanoparticle coating forms which protect them from various barriers inside the body and help in targeted drug delivery

A. Ghosh and R. Srivastava

56 Table 5  Various modifications in NPs for enhanced outcomes Modifications Surface

Encapsulation

Means Polyethylene glycol (PEG) [44–46] Methoxy poly (ethylene glycol) (MPEG), 1,2-dilauroyl-sn-glycerol-3-­­ phosphocholine (DLPC) Vitamin E d-a-succinate polyethylene glycol 1000 (vitamin E TPGS) Polymer or liposome [47, 48]

Goals Mucus layer invasion Increases survival in lung tissues Bypassing macrophages Improved bioavailability Prevention of conjugation with blood proteins by steric hindrance and negative zeta potential.

Improved translocation of nanoparticles. Negative and neutral particles are better translocated. Hollow nanoparticles Increased porosity or hollowness Aerodynamic diameter [46] Determines deep lung deposits Heavy particles are modified to behave like lighter particle equivalents making them easy to disperse in airways Higher aerosolization efficiency sustained release increased bioavailability Nanoparticle Accumulated drug-containing NPs Aggregation then dissociation. aggregates [49] Due to low particle density, large hollow nanoparticulate aggregates with geometric diameters of ~10 μm have aerodynamic diameters of 1–5 μm. Bigger particles limit the likelihood of particles congregating in the inhaler device, ensuring adequate powder administration. Smaller particles avoid deposition anywhere in the respiratory system except the lungs. Nanoparticles with phospholipids on Escape opsonin attack Liposomal the surface [46] Targeted Drug Delivery, polymer nanoparticles addition on liposome-well (Fig. 7a) tolerated due to similarity with tissue proteins Increased phospholipid does not alter morphology but increases porosity. Improves dispersion Simultaneously manufactured Nano-in-micro and nano-in-micro (SIMANIM) one-step Deep lung deposition polymeric Reduces particle–particle spray drying process nanoparticles interaction (Fig. 6) Improved handling and delivery (continued)

Nanomedicines for the Pulmonary Delivery of Antibiotics

57

Table 5 (continued) Modifications Nanocomposites

Means With an excipient, mostly polymer. Poly(dl-lactide-co-glycolide acid) (PLGA) is an FDA-approved, most popular polymer used for nanoparticle delivery due to its safety profile, controlled release properties, and improved colloidal stability. Lipid-polymer Is a hybrid delivery system where the nanoparticle (Fig. 7c) polymer nanoparticle core is enveloped in a liposomal layer. Effervescent Effervescent carrier formulation nanoparticles generally includes sodium bicarbonate, ammonium hydroxide, and citric acid.

Goals The nanocomposite particles had efficient lung deposition, and rapid release of salmon calcitonin occurred.

It possesses combined properties of polymer and liposomal drug delivery. The effervescent reaction generates a force that helps nanoparticles to disperse and avoid aggregation. Thus, effervescence technology has improved release features compared to those that only dissolve.

Fig. 6 (a) describes NP aggregates without micro-particle/carrier-free respirable particles. Dispersion of individual NPs occurs after nebulization. (b) NP with carrier respirable particles. Dispersion of nano-in-macro particles occurs in the lungs, following which individual NPs are released

58

A. Ghosh and R. Srivastava

7C: Polymeric NP

7A: Liposomal NPs

7B: Micelles

7D: Multiporous NPs

7E: Nano rods

Fig. 7  Various forms of nanocarrier systems. (a) Liposomal NPs. (b) Micelles. (c) Polymeric NP. (d) Multiporous NPs. (e) Nano rods

7.6 Bypassing of Phagocytes Increasing the particle size and considering the reach to the distal airways, the optimal size of the particles is engineered to avoid phagocytosis by the macrophages [43]. The long polymeric chain on the surface and liposomal encapsulation contribute to bypassing the reticuloendothelial destruction of the NPs [46, 48].

Nanomedicines for the Pulmonary Delivery of Antibiotics

59

7.7 Physicochemical Characterization Various methods of characterization of NP antimicrobials are as follows: • • • • • •

Differential scanning calorimetry (DSC) Particle size and zeta potential measurements Cell- and animal-based studies Ex vivo lung tissue models In vitro lung epithelial cell culture models In vivo models.

8 Clinical Indications of Inhaled Antimicrobials Inhaled antibiotics are gaining popularity in managing ventilator-associated pneumonia, hospital-acquired pneumonia, SARS-CoV-2 infections and a few more diseases apart from the most successful application on chronic PA infections in CF [50]. The list of drugs and their clinical indications are in Table 6.

Table 6  Clinical indications of inhaled (NP) antibiotics Disease/conditions CF Bronchiectasis

Indications/drugs Chronic bronchial infection with P. aeruginosa. (Presence of the bacteria in at least three sputa samples taken at 1-month intervals during 6 months without exacerbation symptoms.) Drugs:  Fluoroquinolones (levofloxacin/ciprofloxacin liposomes  moxifloxacin-ofloxacin: dried NP, MP  Aztreonam  Amikacin  Tobramycin

Remarks European Cystic Fibrosis Society recommends inhaling tobramycin 28 days on/off or continuously breathing colistin for persistent P. aeruginosa infection and inhaling aztreonam 28 days on/off for further treatment. Tobramycin is given intravenously (not inhaled) during exacerbation. Levofloxacin DPI and liposomal amikacin, new medications in development No research has validated continuous alternating inhalation antibiotics for unstable or worsening illnesses. Inhaled antibiotics may help eradicate a first P. aeruginosa infection in respiratory secretions. (continued)

A. Ghosh and R. Srivastava

60 Table 6 (continued) Disease/conditions Noncystic fibrosis bronchiectasis

Indications/drugs P. aeruginosa infection in non-CF bronchiectasis

Primary ciliary dyskinesia Ataxia telangiectasia

P. aeruginosa infection

Ventilator-associated pneumonia (VAP)

Tuberculosis (under trial) Fungal lung infections

Voriconazole Tacrolimus Itraconazole

P. aeruginosa infection Aminoglycosides (dry powder for inhalation/ solution for inhaling resp) Colistin Fosfomycin Tobramycin Amikacin (liposomes, SLN) Tobramycin-clarithromycin-­ vancomycin (Spray dried NP, MP) Anti-tuberculosis drugs (rifampicin/ethambutol) Amphotericin B Voriconazole Tacrolimus Itraconazol Liposomes Dried NP, MP Spray-dried NP, MP Polymeric NP Lipid NP

Remarks Only a few studies have been conducted with various inhaled antibiotics: amoxicillin, tobramycin, gentamycin, colistin, aztreonam, and, more recently, ciprofloxacin. tobramycin aztreonam tobramycin aztreonam Kollef et al. [51] examined nebulized amikacin and fosfomycin as adjuncts to intravenous antibiotics in VAP patients. Nebulized antibiotics sterilized bronchial secretions faster and reduced drug-­resistant germs, but clinical results were unaffected. Colistin is the most often nebulized antibiotic in critical care units. SLN, polymeric NP, Liposomes Lopisomal Polymeric NP Lipid NP

8.1 Other Aerosolized Antibacterial Medications Two research trials used aerosolized β-lactams. Pines et al. [52] treated P. aeruginosa with aerosolized and intravenous carbenicillin and had a poor response rate. Later, Stoutenbeek et al. [53] found that adding aerosolized cefotaxime or ceftazidime to intravenous treatment for gram-negative bacilli such P. aeruginosa, K. pneumoniae, Escherichia coli, Proteus mirabilis, and Serratia marcescens improved cure rates. Combination and intravenous treatment with broad-spectrum antibacterials might have improved the outcomes in the later studies. Aerosolized vancomycin held promise since MRSA-related VAP was challenging to treat though there was a lack of trial information. In nonacute settings, the only method of eliminating MRSA colonization was the use of aerosolized vancomycin [54, 55].

Nanomedicines for the Pulmonary Delivery of Antibiotics

61

9 Role of Aerosolized Antimicrobials in Multidrug-Resistant Strains Since the function of aerosolized antibiotics in the development of novel drug resistance is unknown, they are usually suggested for administration as part of adjuvant therapy in conjunction with systemic antibiotics rather than as a monotherapy. High-dose nebulized treatment for MDR bacteria shows promise. Nebulized antibiotics for pneumonia have not shown mortality benefits in previous trials. However, VAP caused by MDR gram-negative bacilli (GNB) was more effectively treated with adjuvant aerosolized therapies with nanoforms of antibiotics [56]. In randomized controlled trials, the prevalence of multidrug-resistant bacteria reduced without having an effect on the recurrence of ventilator-associated pneumonia [57, 58]. Nebulized antibiotics in VAP are ineffective and may underestimate serious respiratory episodes, according to the ESCMID policy paper [59]. The panel advised randomized clinical trials of nebulized antibiotics for MDR-associated VAP.  The French Society of Anaesthesia and Intensive Care Medicine (FSAICM) and the French Intensive Care Society (FICS) issued recommendations on hospital-acquired pneumonia (HAP) in the ICU in 2018 [57]. Nebulized colistin and/or aminoglycosides alone for MDR GNB in HAP were advised. The FSAICM and FICS recommended replacement over supplementation for MDR GNB-induced VAP [57].

10 Inhaled Antibiotics in SARS-CoV-2-Infected Patients Nebulized antibiotics may be useful in SARS-CoV-2-infected critically sick patients due to the higher risk of VAP; however, ClinicalTrials.org does not include any such trials. SARS-CoV-2 patients should use mesh nebulizers to minimize reservoir contamination and infectious aerosols. The purpose of an inhaler is to administer a drug in aerosol form straight into the airways or lungs. It is a targeted drug delivery method in which medications are sent directly to a specific part of the lungs, where they will be absorbed more quickly and have a more noticeable impact. Using inhaled aerosols to treat the respiratory system has many pros and cons, as described in Table 7.

10.1 Nebulizers Nebulizers use a compressor to turn liquid medication into a fine mist that can be inhaled through a mouthpiece or mask. Nebulizers provide an ongoing mist of medication that has been aerosolized, allowing a patient to breathe normally while receiving treatment. It usually takes 5–10 minutes for the drug to be delivered using a nebulizer. Drug delivery using a nebulizer is recommended to people, including young children and others having difficulty using other inhalers.

62

A. Ghosh and R. Srivastava

Table 7  Comparisons of various aerosolized drug delivery devices Inhalation device DPI

Advantages Breath actuated convenient portable rapid medication delivery single- and multidose devices the counter indicates the remaining doses

pMDI

Multiple dosing (approximate 100 doses/canister), short administration time, convenient portable

SMI

Multiple dosing possible (around 1 month) High lung deposition Portable No propellants Slow-velocity aerosol generated Aerosol persists for 1.5 seconds, Increasing the ease of synchronizing inhalation with actuation Quick and simple to implement Useful even with low cognitive ability. Negates the need for hand-eye coordination, dexterity, or hand-grip strength

Jet nebulizer

High-efficiency vibrating mesh nebulizer

Portable Quiet Short administration times

Disadvantages REQUIRES the patient’s effort for high inspiratory flow. the challenge for the elderly or patients with  hyperinflation and  flattened diaphragms high probability of pharyngeal and central airway deposition multiple-step process. Patient coordination to synchronize inhalation with pMDI actuation is a challenge. High pharyngeal deposition. Only 10–20% absorption through lungs. Spacers are bulky and require cleaning Multiple steps involved Not breath actuated Not available in most countries

Less portable. Device preparation required Lengthy administration time Daily cleaning required Not all medications are available in this format May not readily aerosolize drug suspensions High cost Device preparation required daily cleaning required Not all medications are available in this format may not readily Aerosolize drug suspensions Optimal doses need to be defined by additional studies to avoid overdosing

DPI dry powder inhaler, HFA hydrofluoroalkane, MDI metered dose inhaler, pMDI pressurized metered dose inhaler, SMI slow mist inhaler

Nanomedicines for the Pulmonary Delivery of Antibiotics

63

11 Importance of the Pharmacokinetic Phase The pharmacokinetics of a drug’s action is the study of its absorption, distribution, metabolism, and elimination over time. The effects of broncho-active aerosols, when inhaled, are limited to the airway. Absorption and systemic distribution lead to unwanted side effects. The drug is carried to the lungs with inhalation, and with swallowing, it is delivered to the stomach via the oropharynx. The dose of the drug that reaches the airway is what has the therapeutic effect. The body absorbs drugs with systemic effects through the lungs and the digestive system. The perfect aerosol would only enter the respiratory system, never the digestive system. Quantifying the efficacy of aerosol delivery to the lung is possible with the lung availability to total systemic availability ratio (L/T ratio). The L/T ratio of Albuterol in MDI and DPI are shown below in Fig. 8a, b, respectively.

12 Challenges Encountered by Nanomedicines Before Entering the Lungs Are (a) In inhalable nanocarrier, the particle size is the main challenge, as it lacks aerodynamic flow property and hence is exhaled while one breathes. (b) Lung fluids in the lining, bacterial biofilm, or lung cells can hamper the drug’s action. (c) Formation of aggregate. (d) Sometimes allergic or concerned toxicity issues are also raised. (e)

Fig. 8 (a, b) depicts the efficiency of aerosol delivery via inhalation route  between MDI and DPI. The L/T ratio determines how much the drug is available for local site vs systemic circulation. More L/T ratio for an inhaled drug indicates that the local effects in the lung are more, and systemic effects are less. (a) Absorption of Albuterol through MDI. (b) Absorption of Albuterol through DPI

64

A. Ghosh and R. Srivastava

Fig. 8 (continued)

Highly expensive when produced in large batches. (f) Limited number of excipients or organic solvents can be used depending on the toxicity profile [60].

13 Ideal Aerosol Antibiotics For effective delivery, the aerosolized medications or antibiotics must have the subsequent characteristics: (a) acts within the physiological pH range, (b) minimum pharmacodynamic inhibition in the presence of other drugs, (c) permeable and effective in the presence of airway secretions, and (d) concentration-dependent (CD) effects for maximal bacterial killing. CD antibiotics do not require a long time to stay in target tissues. However, they are administered frequently to maintain an optimal concentration of the drugs.

14 Pulmonary Delivery for Systemic Antimicrobial Therapy Pulmonary nanocarrier devices can reduce drug dose frequency and improve patient compliance. These inhalable nanocarriers reduce medication serum concentration adverse effects better than oral or intravenous administration [3, 61–64]. The potential long-term danger of excipient toxicity and the nanoscale carrier itself are concerns that need to be considered in the effective product development of pulmonary

Nanomedicines for the Pulmonary Delivery of Antibiotics

65

drug delivery systems, just like with any formulations created for pulmonary drug administration. However, their naturally small size and surface modification provides new possibilities for cutting-edge therapeutic options that not only target pulmonary cells but offer regulated drug release [65–69] for treating systemic infections. Extensive research is required in this field to assess the safety and efficacy of such therapies.

15 Adverse Effects Compared to the parenteral route, the inhalation route reduces major side effects yet may cause systemic and local side effects. Aerosolized antibiotics have few systemic adverse effects, including nephrotoxicity. Medication toxicity depends on drug duration and renal conditions. Drug monitoring is advised while using other nephrotoxic medicines.

15.1 Local Side Effects Nebulization can lead to the development of direct mucosal toxicity. Particularly, long-term exposure to high concentrations of inhaled antibiotics can cause bronchial toxicity and alveolar damage. Though transient benign cough is common, bronchospasm is a more serious but rare side effect that reportedly occurs during antibiotic nebulization [70, 71]. The occurrence of bronchospasm can be diminished by conducting pretreatment with a short-acting bronchodilator. Moreover, increased contact time of the drugs with the pulmonary epithelium and inside the air sacs can potentially adversely affect the respiratory epithelium. However, this requires more research to establish the fact.

15.2 Other Related Complications Nebulization problems, systemic absorption toxicity, and local side effects should all be considered. Mechanical ventilation filters airborne microorganisms and prevents flow and pressure transducer failure. Residual nebulization particles can damage ventilators and circuits. These particles are bigger than mist and can clog filters, increasing resistance and airway pressure [72, 73]. Aerosols and droplets from nebulization can spread infections. In the COVID-19 pandemic, aerosolized medications may transmit the virus to healthcare personnel. Healthcare personnel must be protected for more than 3 hours after nebulization, and nebulized aerosols may contaminate the environment.

66

A. Ghosh and R. Srivastava

16 Current Recommendations The Infectious Diseases Society of America/American Thoracic Society guidelines for nosocomial pneumonia recommends (weak recommendation, low quality of evidence) adding inhaled antibiotics to systemic antibiotics regime for gram-negative pneumonia caused by MDR pathogens sensitive only to polymyxins and aminoglycosides [74]. The guidelines suggest inhaling colistin over polymyxin B. This treatment might be a final resort for nonresponding VAP patients with sensitive or resistant infections. The European nosocomial pneumonia recommendations did not discuss inhaled antibiotics until further evidence was available [13]. Even for high-risk patients, inhaled antibiotics are not recommended as supplementary therapy. However, some studies support its use once culture data shows MDR bacteria or as salvage therapy [59]. Empiric adjunctive aerosolized treatment is not routinely used. Regular adjunctive treatment may benefit objectives linked to systemic antibiotic usage in future studies if correctly structured. Apart from the antimicrobial efficacy improving patient tolerance is very important in mechanically ventilated patients. The following measures are useful in improving the aerosol delivery and are mentioned in Table 8.

17 Clinical Trials of Aerosolized Antibiotics In animal experiments, nebulized aminoglycosides and colimycin (polymyxin E) increase antibiotic concentrations and kill sensitive or MDR gram-negative bacteria (GNB) in the lung parenchyma [76]. Nebulized aminoglycosides and colimycin may be better for ventilator-associated pneumonia (VAP) patients than IV administration; however, this has not been clinically proven in human subjects. The previous clinical trials had employed a range of varying methods, and most of those had Table 8  Recommendations for improved aerosol therapy in mechanically ventilated patients [75] Improving delivery of aerosolized medications  Flow rate >= 6 l/min  Inspiratory flow triggered nebulization  MMAD 1–5 μm for a jet nebulizer  Before giving, compound doses should be used to thoroughly fill the chamber of the nebulizer.  Insert nebulizer into inspiratory loop 30 cm away from the endotracheal tube.  During nebulization, turn off the humidifier. Improving tolerance in mechanically ventilated patients  Stop humidification during nebulization.  Drugs: pH between 4.0 and 8.0, osmolarity between 150 and 200 mOsm/l, normal saline as diluent, consider aerosolized tobramycin in case of adverse reactions with IV tobramycin; after preparation, administer colistin immediately.

Nanomedicines for the Pulmonary Delivery of Antibiotics

67

a small sample size. Recommendations of US and European academic societies for nebulized antibiotics are limited, based on inadequate and sometimes contradicting data. A few clinical studies (Table 9) for the last two decades have been conducted on aerosolized antibiotics, which chiefly revealed benefits in clinical outcomes but negligible differences in mortality, hospital stay, and overall outcome in ventilator-­ associated pneumonia (VAP) and hospital-acquired pneumonia (HAP). In 2016, the Infectious Disease Society of America (IDSA)/American Thoracic Society (ATS) revised VAP Guidelines and advised treating VAP caused by GNB, which are only sensitive to aminoglycosides or polymyxins, using both nebulized and intravenous medications [77]. In 2017, the European Society of Clinical Microbiology and Infectious Diseases made a position paper about VAP and the use of nebulized antibiotics [78] which includes (a) avoiding routine use of nebulized antibiotics because of limited data on lung complications; (b) using vibrating mesh nebulizers with optimized ventilator settings and specific ventilator circuits to limit inertial impaction of aerosolized particles in the tracheobronchial tree and promote distal lung deposition [79], and; (c) doing randomized clinical trials (RCTs) of nebulized antibiotic therapy. In 2018, the French Society of Anesthesia and Intensive Care Medicine and the French Intensive Care Society suggested nebulized colimycin and/or aminoglycosides for VAP caused by MDR GNB responsive to these antibiotics when no other antibiotics can be administered (low level of evidence, strong agreement) [80]. In 2019, the 2016 American guidelines were modified to administer nebulized amikacin or colimycin for VAP due to GNB only sensitive to aminoglycosides or polymyxins on top of IV antibiotics or in patients not responding to IV antibiotics alone, whether the underlying bacteria is MDR or not [81]. Three RCTs on the use of nebulized aminoglycosides with IV cephalosporins in VAP published between 2017 and 2020 [82–84] failed to demonstrate any benefits. These are listed below. • IASIS (Aerosolized Amikacin and Fosfomycin in Mechanically Ventilated Patients with gram-negative Pneumonia). • INHALE ((Inhaled amikacin adjunctive to IV standard-of-care antibiotics in mechanically ventilated patients with gram-negative VAP), and • VAPORIZE (Adjunctive tobramycin inhalation vs placebo on early clinical response in the treatment of VAP) aminoglycosides failed three RCTs. Their tactics may be to blame. Possible reasons for the failure of the above trials are as follows: • IV beta-lactams are very successful for severely ill VAP patients with sensitive GNB; therefore, nebulized aminoglycosides are unlikely to help. • The mistaken expectation that modest nebulized aminoglycoside doses would provide substantial alveolar concentrations led to negligible lung deposition and no bactericidal effect at the infection site. • The three trials did not optimize breathing settings for deep lung deposition of nebulized antibiotics.

AS amikacin 300 mg/ fosfomycin 120 mg twice daily

143 VAP

Double-blinded RCT

(2017) Kollef et al. [86]

placebo, with IV IV Colistin alone IV colistin LD placebo, with IV antibiotics 9 MIU + 4.5 meropenem or MIU BID, imipenem with IV imipenem

149 VAP

(2016) Abdellatif et al. [87] Single-blind RCT

AS colistin CBA AS colistin and AS colistin 4 75 mg) twice intravenous (IV) MIU thrice daily colistin daily

(2015) Valachis et al. [86] Meta-analysis: 7 observational or case-control studies: 1 RCT 690 VAP

Intervention Aerosolized group (AS) aminoglycosides delivered through endotracheally Control placebo, with IV group or IM antibiotics

(2010) Rattanaumpawan et al. [70] Open-label RCT

100 VAP

(2007) Ioannidou et al. [85] Meta-analysis :5 RCTs

Participants 176 Disease HAP

Year Conducted by Type

Table 9  Clinical trials on aerosolized antibiotics

IV aminoglycosides or colistin, with IV antibiotics

AS aminoglycosides or colistin ± IV aminoglycosides or colistin

826 VAP or VAT

(2017) Sole-Lleonart et al. [58] Meta-analysis: 6 RCT and 5 observational studies

IV amikacin 20 mg/kg once daily, with IV piperacillin/ tazobactam

133 Postcardiac surgery HAP, or VAP AS amikacin 400 mg twice daily

(2018) Hassan et al. [88] Open-label RCT

vs. placebo, with IV antibiotics

725 Gram-­ negative pneumonia under MV AS amikacin 400 mg twice daily

(2020) Niederman et al. [89] Double-­ blind RCT

No difference

No difference

No difference

Mortality

Microbial eradication rate

Drug-­ related adverse event

No difference

High microbial eradication rate

No difference

High success rates

No difference

No difference

No difference in mortality and clinical relapse rates

Few positive tracheal cultures on days 3 and 7 with AS amikacin/ fosfomycin; no difference in CPIS change

Less No difference nephrotoxicity with AS colistin

Improvement in improvement clinical response in respiratory failure (PaO2/ FiO2 ratio), shortened time to microbial eradication, early weaning from MV Better infection-­ No difference related mortality in clinical with AS + IV cure rates, colistin length of stay, No difference in and 28-day overall mortality mortality Microbial No difference eradication rate No difference in mortality

High clinical cure rates with AS amikacin on day 7, shortened ICU stay and MV duration

No difference in pneumonia-­ related mortality Not reported

No difference in survival until day 28–32, the duration of MV and ICU stay

Few positive tracheal No difference cultures on days 3 and 7 with AS amikacin/fosfomycin Less nephrotoxicity Less No compromised MV in nephrotoxicity difference hypoxemic patients

No difference in mortality

High clinical cure rates with AS antibiotics in VAP with drug-resistant pathogens, no difference in MV duration

AS aerosolized, CPIS clinical pulmonary infection score, CBA colistin base activity, HAP hospital-acquired pneumonia, ICU intensive care units, IM intramuscular, IV intravenous, LD loading dose, MIU million international units, MV mechanical ventilation, RCT randomized control trial, VAP ventilator-associated pneumonia, VAT ventilator-associated tracheobronchitis

High success rates

Outcome

70

A. Ghosh and R. Srivastava

The failure of the IASIS, INHALE, and VAPORIZE studies does not rule out the utility of nebulized antibiotics. Instead, it calls for RCTs comparing high-dose nebulized (40 mg/kg) amikacin to IV (20 mg/kg) in VAP caused exclusively by MDR GNB and employing refined nebulization procedures. Future RCTs may use nebulized aminoglycosides to increase MDR VAP clinical cure rates by 15%. If a benefit is seen, randomized controlled trials with many MDR gram-negative ventilator-­ associated pneumonia patients might assess mortality.

18 Regulatory Hurdles To create a nanodrug based on pharmaceuticals, certain regulatory manufacturing standards must be followed throughout drug production. Nanodrugs made from existing micro-formulations are authorized faster, while innovative products require more stringent examination and clearance [90]. New nanomedicine manufacturers must follow FDA (Current Appropriate Manu—Invoicing Practices) and Quality Control Regulations. Effective clinical translation requires the evaluation of nanoparticle toxicity data. However, delivery of NPs by intravenous (IV) might result in NP accumulation in the liver, lung, spleen, and bone marrow [91]. The interaction of NPs with cells that cause oxidative stress and lead to hepatotoxicity and pulmonary toxicity is seen in several instances [92, 93]. Hepatotoxicity and nephrotoxicity are allegedly caused by suggested metabolic changes such as mitochondrial malfunction, reduced ketogenesis, beta-oxidation of fatty acids, and glycolysis [94]. There are no widely accepted ways for universal NP dosage, despite the fact that existing in vitro techniques have certain benefits since nanoparticles function in a size-specific manner. Additional characterization techniques are needed to address this issue. Delivering specific microorganisms is the major focus of more recent research.

19 Conclusion Nebulized antibiotic therapy tailored with nanotechnology can be useful in many ways like targeted therapy, reducing systemic toxicity, and reducing various physiological and pathobiological barriers. However, their administration through a pulmonary bed is not easy and requires an in-depth understanding of not only the aerosol mechanics but also about the optimum drug delivery methods and devices. With the combination of nebulized and systemic antibiotic therapy, especially in the VAP and HAP cases, much better outcome is expected. Nanomedicines have their challenges in scaling up, and there are regulatory hurdles. However, nebulized nanoantibiotics are evolving rapidly as a much promising future of drug delivery through the pulmonary route, especially in MDR strains.

Nanomedicines for the Pulmonary Delivery of Antibiotics

71

References 1. Breasted JH.  The Edwin Smith Surgical Papyrus: published in facsimile and hieroglyphic transliteration with translation and commentary in two volumes, 1930. 2. Jaafar-Maalej C, Elaissari A, Fessi H. Lipid-based carriers: manufacturing and applications for pulmonary route. Expert Opin Drug Deliv. 2012;9:1111–27. 3. Sung JC, Pulliam BL, Edwards DA.  Nanoparticles for drug delivery to the lungs. Trends Biotechnol. 2007;25:563–70. 4. Collaborators GBD, Ärnlöv J. Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet. 2020;396:1223–49. 5. Velkov T, Abdul Rahim N, Zhou Q, (Tony), Chan H-K, Li J. Inhaled anti-infective chemotherapy for respiratory tract infections: successes, challenges and the road ahead. Adv Drug Deliv Rev. 2015;85:65–82. 6. José RJ, Periselneris JN, Brown JS. Opportunistic bacterial, viral and fungal infections of the lung. Medicine. 2020;48:366–72. 7. Carfì A, Bernabei R, Landi FG. Against COVID-19. Post-Acute Care Study Group: for the Gemelli against CCOVID-19 Post-Acute Care Study Group. Persistent symptoms in patients after acute COVID-19. JAMA. 2020;324:9. 8. Chopra V, Flanders SA, O’Malley M, Malani AN, Prescott HC. Sixty-day outcomes among patients hospitalized with COVID-19. Ann Intern Med. 2021;174:576–8. 9. Bardhan N. Nanomaterials in diagnostics, imaging and delivery: applications from COVID-19 to cancer. MRS Commun. 2022;12:1–21. 10. Hickey AJ.  Controlled delivery of inhaled therapeutic agents. J Control Release. 2014;190:182–8. 11. Kannan RM, Nance E, Kannan S, Tomalia DA. Emerging concepts in dendrimer‐based nanomedicine: from design principles to clinical applications. J Intern Med. 2014;276:579–617. 12. Khan YS, Lynch DT.  Histology, Lung. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan. Available from: https://www.ncbi.nlm. nih.gov/books/NBK534789/ 13. Leiby KL, Raredon MSB, Niklason LE.  Bioengineering the blood‐gas barrier. In: Compr Physiol. Wiley; 2020. p. 415–52. 14. Persson P, Lundin S, Stenqvist O. Transpulmonary and pleural pressure in a respiratory system model with an elastic recoiling lung and an expanding chest wall. Intensive Care Med Exp. 2016;4:26. 15. Cantor B.  Fick’s Laws. In: The equations of materials. Oxford University Press; 2020. p. 141–61. 16. Schürch S, Qanbar R, Bachofen H, Possmayer F. The surface-associated surfactant reservoir in the Alveolar lining. Neonatology. 1995;67:61–76. 17. Balaei-Kahnamoei M, Al-Attar M, Khazaneha M, Raeiszadeh M, Ghorbannia-Dellavar S, Bagheri M, Salimi-Sabour E, Shahriary A, Arabfard M. Overview of herbal therapy of acute and chronic pulmonary disease: a conceptual map. Library Hi Tech. 2022:20221215. 18. Muralidharan P, Malapit M, Mallory E, Hayes D, Mansour HM.  Inhalable nanoparticulate powders for respiratory delivery. Nanomedicine. 2015;11:1189–99. 19. Praphawatvet T, Peters JI, Williams RO III.  Inhaled nanoparticles–an updated review. Int J Pharm. 2020;587:119671. 20. Pramanik S, Mohanto S, Manne R, Rajendran RR, Deepak A, Edapully SJ, Patil T, Katari O.  Nanoparticle-based drug delivery system: the magic bullet for the treatment of chronic pulmonary diseases. Mol Pharm. 2021;18:3671–718. 21. Cheng YS. Mechanisms of pharmaceutical aerosol deposition in the respiratory tract. AAPS PharmSciTech. 2014;15:630–40.

72

A. Ghosh and R. Srivastava

22. Ehtezazi T, Davies MJ, Seton L, Morgan MN, Ross S, Martin GD, Hutchings IM. Optimizing the primary particle size distributions of pressurized metered dose inhalers by using inkjet spray drying for targeting desired regions of the lungs. Drug Dev Ind Pharm. 2015;41:279–91. 23. Ramli SF, Aziz HA, Omar FM, Yusoff MS, Halim H, Kamaruddin MA, Ariffin KS, Hung YT. Influence of Particle Size and Zeta Potential in Treating Highly Coloured Old Landfill Leachate by Tin Tetrachloride and Rubber Seed. Int J Environ Res Public Health. 2022;19(5):3016. https://doi.org/10.3390/ijerph19053016. PMID: 35270706; PMCID: PMC8910293. 24. Yang W, Peters JI, Williams RO III.  Inhaled nanoparticles—a current review. Int J Pharm. 2008;356:239–47. 25. Darquenne C.  Aerosol deposition in health and disease. J Aerosol Med Pulm Drug Deliv. 2012;25:140–7. 26. Tien C, Ramarao BV. 4 - MECHANISMS OF PARTICLE DEPOSITION. In: Tien C, Ramarao BV, editors. Granular filtration of aerosols and hydrosols. 2nd ed. Oxford: Butterworth-­ Heinemann; 2007. p. 117–68. 27. Pitre L, Plimmer MD, Sparasci F, Himbert ME. Determinations of the Boltzmann constant. C R Phys. 2019;20:129–39. 28. Coates AL, MacNeish CF, Meisner D, Thibert R, Vadas E, Kelemen S, MacDonald J.  The choice of jet nebulizer, nebulizing flow, and addition of albuterol affects the output of tobramycin aerosols. Chest. 1997;111:1206–12. 29. Diot P, Dequin PF, Rivoire B, Gagnadoux F, Faurisson F, Diot E, Boissinot E, le Pape A, Palmer L, Lemarie E. Aerosols and anti-infectious agents. J Aerosol Med. 2001;14:55–64. 30. Newman SP, Woodman G, Clarke SW. Deposition of carbenicillin aerosols in cystic fibrosis: effects of nebuliser system and breathing pattern. Thorax. 1988;43:318–22. 31. Knap K, Kwiecień K, Reczyńska-Kolman K, Pamuła E. Inhalable microparticles as drug delivery systems to the lungs in a dry powder formulations. Regen Biomater. 2023; https://doi. org/10.1093/rb/rbac099. 32. Ziesmer, J. (2023). Hybrid Antibacterial Microneedle Patches Against Skin Infections (Doctoral dissertation, Karolinska Institutet (Sweden)). 33. Laube, Beth L, Rajkumari N. Jashnani, Richard R. N. Dalby and Pamela L Zeitlin. “Targeting aerosol deposition in patients with cystic fibrosis: effects of alterations in particle size and inspiratory flow rate.” Chest 118 4 (2000): 1069–76. 34. Brand P, Meyer T, Häussermann S, Schulte M, Scheuch G, Bernhard T, Sommerauer B, Weber N, Griese M. Optimum peripheral drug deposition in patients with cystic fibrosis. J Aerosol Med. 2005;18:45–54. 35. Trottier ED, Doré-Bergeron M-J, Chauvin-Kimoff L, Baerg K, Ali S.  Managing pain and distress in children undergoing brief diagnostic and therapeutic procedures. Paediatr Child Health. 2019;24:509–21. 36. Berkenfeld K, Lamprecht A, McConville JT. Devices for dry powder drug delivery to the lung. AAPS PharmSciTech. 2015;16:479–90. 37. Kristensen MS, McGuire B. Managing and securing the bleeding upper airway: a narrative review. Can J Anesth. 2020;67:128–40. 38. Fauci AS.  Infectious diseases: considerations for the 21st century. Clin Infect Dis. 2001;32:675–85. 39. Hadinoto K, Cheow WS.  Nano-antibiotics in chronic lung infection therapy against Pseudomonas aeruginosa. Colloids Surf B Biointerfaces. 2014;116:772–85. 40. Huh AJ, Kwon YJ. “Nanoantibiotics”: a new paradigm for treating infectious diseases using nanomaterials in the antibiotics resistant era. J Control Release. 2011;156:128–45. 41. Gupta A, Mumtaz S, Li C-H, Hussain I, Rotello VM. Combatting antibiotic-resistant bacteria using nanomaterials. Chem Soc Rev. 2019;48:415–27. 42. Deacon J, Abdelghany SM, Quinn DJ, et al. Antimicrobial efficacy of tobramycin polymeric nanoparticles for Pseudomonas aeruginosa infections in cystic fibrosis: formulation, characterisation and functionalisation with dornase alfa (DNase). J Control Release. 2015;198:55–61.

Nanomedicines for the Pulmonary Delivery of Antibiotics

73

43. Chow AHL, Tong HHY, Chattopadhyay P, Shekunov BY. Particle engineering for pulmonary drug delivery. Pharm Res. 2007;24:411–37. 44. Knop K, Hoogenboom R, Fischer D, Schubert US. Poly (ethylene glycol) in drug delivery: pros and cons as well as potential alternatives. Angew Chem Int Ed. 2010;49:6288–308. 45. Chung HA, Kato K, Itoh C, Ohhashi S, Nagamune T. Casual cell surface remodeling using biocompatible lipid‐poly (ethylene glycol)(n): development of stealth cells and monitoring of cell membrane behavior in serum‐supplemented conditions. J Biomed Mater Res A. 2004;70:179–85. 46. Hadinoto K, Phanapavudhikul P, Kewu Z, Tan RBH.  Dry powder aerosol delivery of large hollow nanoparticulate aggregates as prospective carriers of nanoparticulate drugs: effects of phospholipids. Int J Pharm. 2007;333:187–98. 47. Mahmud A, Discher DE.  Lung vascular targeting through inhalation delivery: insight from filamentous viruses and other shapes. IUBMB Life. 2011;63:607–12. 48. Thorley AJ, Tetley TD. New perspectives in nanomedicine. Pharmacol Ther. 2013;140:176–85. 49. Edwards DA, Hanes J, Caponetti G, Hrkach J, Ben-Jebria A, Lou EM, Mintzes J, Deaver D, Lotan N, Langer R. Large porous particles for pulmonary drug delivery. Science (1979). 1997;276:1868–72. 50. Taccetti G, Francalanci M, Pizzamiglio G, Messore B, Carnovale V, Cimino G, Cipolli M.  Cystic fibrosis: recent insights into inhaled antibiotic treatment and future perspectives. Antibiotics. 2021;10:338. 51. Kollef MH, Ricard J-D, Roux D, Francois B, Ischaki E, Rozgonyi Z, Boulain T, Ivanyi Z, János G, Garot D. A randomized trial of the amikacin fosfomycin inhalation system for the adjunctive therapy of Gram-negative ventilator-associated pneumonia: IASIS trial. Chest. 2017;151:1239–46. 52. Pines A, Raafat H, Siddiqui GM, Greenfield JSB. Treatment of severe pseudomonas infections of the bronchi. Br Med J. 1970;1:663–5. 53. Stoutenbeek CP, Van Saene HKF, Miranda DR, Zandstra DF, Langrehr D. Nosocomial gram-­ negative pneumonia in critically ill patients: a 3-year experience with a novel therapeutic regimen. Intensive Care Med. 1986;12:419–23. 54. Gradon JD, Wu EH, Lutwick LI. Aerosolized vancomycin therapy facilitating nursing home placement. Ann Pharmacother. 1992;26:209–10. 55. Solis A, Brown D, Hughes J, Van Saene HKF, Heaf DP. Methicillin‐resistant Staphylococcus aureus in children with cystic fibrosis: an eradication protocol. Pediatr Pulmonol. 2003;36:189–95. 56. Lu Q, Yang J, Liu Z, Gutierrez C, Aymard G, Rouby J-J, Group NAS. Nebulized ceftazidime and amikacin in ventilator-associated pneumonia caused by Pseudomonas aeruginosa. Am J Respir Crit Care Med. 2011;184:106–15. 57. Leone M, Bouadma L, Bouhemad B, Brissaud O, Dauger S, Gibot S, Hraiech S, Jung B, Kipnis E, Launey Y.  Hospital-acquired pneumonia in ICU.  Anaesth Crit Care Pain Med. 2018;37:83–98. 58. Sole-Lleonart C, Rouby J-J, Blot S, Poulakou G, Chastre J, Palmer LB, Bassetti M, Luyt C-E, Pereira JM, Riera J. Nebulization of antiinfective agents in invasively mechanically ventilated adults: a systematic review and meta-analysis. Anesthesiology. 2017;126:890–908. 59. Rello J, Solé-Lleonart C, Rouby J-J, Chastre J, Blot S, Poulakou G, Luyt C-E, Riera J, Palmer LB, Pereira JM.  Use of nebulized antimicrobials for the treatment of respiratory infections in invasively mechanically ventilated adults: a position paper from the European Society of Clinical Microbiology and Infectious Diseases. Clin Microbiol Infect. 2017;23:629–39. 60. Sanchis J, Corrigan C, Levy ML, Viejo JL. Inhaler devices–from theory to practice. Respir Med. 2013;107:495–502. 61. Beck-Broichsitter M, Gauss J, Gessler T, Seeger W, Kissel T, Schmehl T. Pulmonary targeting with biodegradable salbutamol-loaded nanoparticles. J Aerosol Med Pulm Drug Deliv. 2010;23:47–57.

74

A. Ghosh and R. Srivastava

62. Moreno-Sastre M, Pastor M, Salomon CJ, Esquisabel A, Pedraz JL. Pulmonary drug delivery: a review on nanocarriers for antibacterial chemotherapy. J Antimicrob Chemother. 2015;70:2945–55. 63. d’Angelo I, Conte C, Miro A, Quaglia F, Ungaro F. Pulmonary drug delivery: a role for polymeric nanoparticles? Curr Top Med Chem. 2015;15:386–400. 64. Lim YH, Tiemann KM, Hunstad DA, Elsabahy M, Wooley KL. Polymeric nanoparticles in development for treatment of pulmonary infectious diseases. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2016;8:842–71. 65. Chakraborty A, Selomulya C. Formulation and role of polymeric and inorganic nanoparticles in respiratory diseases. In: Targeting chronic inflammatory lung diseases using advanced drug delivery systems. Elsevier; 2020. p. 261–80. 66. Sabuj MZR, Islam N. Inhaled antibiotic-loaded polymeric nanoparticles for the management of lower respiratory tract infections. Nanoscale Adv. 2021;3:4005–18. 67. van Rijt SH, Bein T, Meiners S. Medical nanoparticles for next generation drug delivery to the lungs. Eur Resp J. 2014;44:201409. 68. Kumadoh D, Adi-Dako O, Osei YA, Archer MA. Recent trends in applications of nano-drug delivery systems. In: Handbook of lung targeted drug delivery systems. CRC Press; 2021. p. 225–38. 69. Mansour HM, Park CW, Bawa R.  Design and development of approved nanopharmaceuticals products. Handbook of Clinical Nanomedicine-FromBench to Bedside, Pan Stanford Publishing Pvt. Ltd. Singapore. 2015;1–33 70. Rattanaumpawan P, Lorsutthitham J, Ungprasert P, Angkasekwinai N, Thamlikitkul V. Randomized controlled trial of nebulized colistimethate sodium as adjunctive therapy of ventilator-associated pneumonia caused by Gram-negative bacteria. J Antimicrob Chemother. 2010;65:2645–9. 71. Luyt C-E, Clavel M, Guntupalli K, Johannigman J, Kennedy JI, Wood C, Corkery K, Gribben D, Chastre J. Pharmacokinetics and lung delivery of PDDS-aerosolized amikacin (NKTR-061) in intubated and mechanically ventilated patients with nosocomial pneumonia. Crit Care. 2009;13:1–10. 72. Palmer LB, Smaldone GC, Simon SR, O’Riordan TG, Cuccia A. Aerosolized antibiotics in mechanically ventilated patients: delivery and response. Crit Care Med. 1998;26:31–9. 73. Demers RR. Bacterial/viral filtration: let the breather beware! Chest. 2001;120:1377–89. 74. Kalil AC, Metersky ML, Klompas M, Muscedere J, Sweeney DA, Palmer LB, Napolitano LM, O’Grady NP, Bartlett JG, Carratalà J. Management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016;63:e61–e111. 75. Wood GC, Swanson JM.  Aerosolised Antibacterials for the prevention and treatment of hospital-­acquired pneumonia. Drugs. 2007;67:903–14. 76. Rouby J-J, Bouhemad B, Monsel A, Brisson H, Arbelot C, Lu Q. Aerosolized antibiotics for ventilator-associated pneumonia. Anesthesiology. 2012;117:1364–80. 77. Kalil AC, Metersky ML, Klompas M, et al. Executive summary: management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016;63:575–82. 78. Rello J, Solé-Lleonart C, Rouby J-J, et al. Use of nebulized antimicrobials for the treatment of respiratory infections in invasively mechanically ventilated adults: a position paper from the European Society of Clinical Microbiology and Infectious Diseases. Clin Microbiol Infect. 2017;23:629–39. 79. Rello J, Rouby JJ, Sole-Lleonart C, et al. Key considerations on nebulization of antimicrobial agents to mechanically ventilated patients. Clin Microbiol Infect. 2017;23:640–6. 80. Leone M, Bouadma L, Bouhemad B, et al. Hospital-acquired pneumonia in ICU. Anaesth Crit Care Pain Med. 2018;37:83–98.

Nanomedicines for the Pulmonary Delivery of Antibiotics

75

81. Sweeney DA, Kalil AC.  Why don’t we have more inhaled antibiotics to treat ventilator-­ associated pneumonia? Clin Microbiol Infect. 2019;25:1195–9. 82. Kollef MH, Ricard J-D, Roux D, et al. A randomized trial of the Amikacin Fosfomycin inhalation system for the adjunctive therapy of gram-negative ventilator-associated pneumonia. Chest. 2017;151:1239–46. 83. Niederman MS, Alder J, Bassetti M, et  al. Inhaled amikacin adjunctive to intravenous standard-­of-care antibiotics in mechanically ventilated patients with Gram-negative pneumonia (INHALE): a double-blind, randomised, placebo-controlled, phase 3, superiority trial. Lancet Infect Dis. 2020;20:330–40. 84. Stokker J, Karami M, Hoek R, Gommers D, van der Eerden M. Effect of adjunctive tobramycin inhalation versus placebo on early clinical response in the treatment of ventilator-associated pneumonia: the VAPORISE randomized-controlled trial. Intensive Care Med. 2020;46:546–8. 85. Ioannidou E, Siempos II, Falagas ME.  Administration of antimicrobials via the respiratory tract for the treatment of patients with nosocomial pneumonia: a meta-analysis. J Antimicrob Chemother. 2007;60:1216–26. 86. Valachis A, Samonis G, Kofteridis DP.  The role of aerosolized colistin in the treatment of ventilator-associated pneumonia: a systematic review and metaanalysis. Crit Care Med. 2015;43:527–33. 87. Abdellatif S, Trifi A, Daly F, Mahjoub K, Nasri R, Ben Lakhal S.  Efficacy and toxicity of aerosolised colistin in ventilator-associated pneumonia: a prospective, randomised trial. Ann Intensive Care. 2016;6:1–11. 88. Hassan NA, Awdallah FF, Abbassi MM, Sabry NA. Nebulized versus IV amikacin as adjunctive antibiotic for hospital and ventilator-acquired pneumonia postcardiac surgeries: a randomized controlled trial. Crit Care Med. 2018;46:45–52. 89. Niederman MS, Alder J, Bassetti M, Boateng F, Cao B, Corkery K, Dhand R, Kaye KS, Lawatscheck R, McLeroth P.  Inhaled amikacin adjunctive to intravenous standard-of-care antibiotics in mechanically ventilated patients with Gram-negative pneumonia (INHALE): a double-blind, randomised, placebo-controlled, phase 3, superiority trial. Lancet Infect Dis. 2020;20:330–40. 90. Hoet PHM, Brüske-Hohlfeld I, Salata OV. Nanoparticles–known and unknown health risks. J Nanobiotechnol. 2004;2:1–15. 91. Nijhara R, Balakrishnan K. Bringing nanomedicines to market: regulatory challenges, opportunities, and uncertainties. Nanomedicine. 2006;2:127–36. 92. Hagens WI, Oomen AG, de Jong WH, Cassee FR, Sips AJAM.  What do we (need to) know about the kinetic properties of nanoparticles in the body? Regul Toxicol Pharmacol. 2007;49:217–29. 93. Sandhiya S, Dkhar SA, Surendiran A. Emerging trends of nanomedicine–an overview. Fundam Clin Pharmacol. 2009;23:263–9. 94. De Jong WH, Borm PJA.  Drug delivery and nanoparticles: applications and hazards. Int J Nanomedicine. 2008;3:133–49.

Inhalable Nanomedicines for the Treatment of Pulmonary Aspergillosis Basanth Babu Eedara, David Encinas-Basurto, Bhagyashree Manivannan, Don Hayes Jr, and Heidi M. Mansour

Abstract  Pulmonary aspergillosis is a serious pulmonary fungal infection and a major cause of morbidity and mortality in immunocompromised patients. The current treatment for pulmonary aspergillosis includes the delivery of antifungal drugs via oral and/or parenteral routes. However, the current routes of administration are associated with many challenges such as poor oral absorption and oral bioavailability, systemic toxicity, and low drug concentration at the site of action. Thus, more effective treatment with direct and targeted delivery of the drugs to the site of action is required. Pulmonary delivery is a promising route of administration for the delivery of antifungal drugs directly to the site of infection, i.e., lungs. This chapter will describe the pulmonary delivery of antifungal drugs for the treatment of pulmonary aspergillosis. It covers a summary of current treatment and drugs used for the treatment of pulmonary aspergillosis and their mechanism of action, inhalation delivery of antifungal drugs, and a description of the reported inhaled antifungal nanomedicine pulmonary delivery systems. Keywords  Pulmonary aspergillosis · Inhalation · Antifungal drugs · Nanocarriers · Microparticles

B. B. Eedara · B. Manivannan · H. M. Mansour (*) Center for Translational Science, Florida International University, Port St. Lucie, FL, USA e-mail: [email protected] D. Encinas-Basurto Department of Physics, Mathematics and Engineering, University of Sonora, Navojoa, Sonora, Mexico D. Hayes Jr Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA Division of Pulmonary, Critical Care, and Sleep Medicine, University of Cincinnati Medical Center, Cincinnati, OH, USA Department of Pediatrics and Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 V. B. Patravale et al. (eds.), Nanomedicines for the Prevention and Treatment of Infectious Diseases, AAPS Advances in the Pharmaceutical Sciences Series 56, https://doi.org/10.1007/978-3-031-39020-3_3

77

78

B. B. Eedara et al.

1 Introduction Pulmonary aspergillosis has several patterns of disease with considerable overlap and a wide variation in severity. With these characteristics along with limited research in the field, pulmonary aspergillosis is a respiratory condition that will undoubtedly evolve and undergo further changes in its definition and management in the future. At present, there are acute and chronic forms of pulmonary aspergillosis, with subacute invasive pulmonary aspergillosis falling somewhere in between. The differences between acute and subacute forms of the disease are based on the timing of progression of up to a month versus 1–3 months, respectively [1]. The manifestations of chronic pulmonary aspergillosis include aspergilloma, Aspergillus nodules, chronic cavitary pulmonary aspergillosis, and chronic fibrosing pulmonary aspergillosis [1]. Although the pathophysiology of pulmonary aspergillosis is not completely understood, it appears that risk factors for the acute and subacute forms are different compared to the chronic form. There is some evidence that immunosuppression is a risk factor for acute and subacute forms of pulmonary aspergillosis while prior lung damage or lung disease is a risk factor for chronic pulmonary aspergillosis. The clinical features of pulmonary aspergillosis are nonspecific and can occur over months, often leading to a delay in the diagnosis. The signs and symptoms associated with chronic pulmonary aspergillosis include weight loss, cough, dyspnea, and hemoptysis rather than fatigue/malaise, chest pain, and fever, which may be more common in acute and subacute forms [2, 3]. Radiographic imaging is often used for diagnostic purposes when assessing a patient for pulmonary aspergillosis with cavities detectable with or without fungus balls. Figure 1 details an example of both a plain radiograph and a computed tomography scan of the chest identifying Aspergillus fumigatus in a patient. Additional diagnostic tests available include

Fig. 1  Plain radiograph (a) and computed tomography scan of the chest (b) showing a left upper lobe cavitary lesion with a fungus ball in a 17-year-old with a history of acute lymphocytic leukemia and ongoing neutropenia (absolute neutrophil count