Electrostatically entrapped colistin liposomes for the treatment of Pseudomonas aeruginosa infection

Lipid-based nanomedicines for the treatment of bacterial respiratory infections: current state and new perspectives

The global threat posed by antimicrobial resistance demands urgent action and the development of effective drugs. Lower respiratory tract infections remain the deadliest communicable disease worldwide, often challenging to treat due to the presence of bacteria that form recalcitrant biofilms. There is consensus that novel anti-infectives with reduced resistance compared with conventional antibiotics are needed, leading to extensive research on innovative antibacterial agents. This review explores the recent progress in lipid-based nanomedicines developed to counteract bacterial respiratory infections, especially those involving biofilm growth; focuses on improved drug bioavailability and targeting and highlights novel strategies to enhance treatment efficacy while emphasizing the importance of continued research in this dynamic field.

Advanced delivery systems for peptide antibiotics

Antimicrobial peptides (AMPs) hold promise as alternatives to traditional antibiotics for preventing and treating multidrug-resistant infections. Although they have potent antimicrobial efficacy, AMPs are mainly limited by their susceptibility to proteases and potential off-site cytotoxicity. Designing the right delivery system for peptides can help to overcome such limitations, thus improving the pharmacokinetic and pharmacodynamic profiles of these drugs. The versatility of peptides and their genetically encodable structure make them suitable for both conventional and nucleoside-based formulations. In this review, we describe the main drug delivery procedures developed so far for peptide antibiotics: lipid nanoparticles, polymeric nanoparticles, hydrogels, functionalized surfaces, and DNA- and RNA-based delivery systems.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

99mTc-Labeled, Colistin Encapsulated, Theranostic Liposomes for Pseudomonas aeruginosa Infection

Infectious diseases are still the major issue not only due to antibiotic resistance but also causing deaths if not diagnosed at early-stages. Different approaches including nanosized drug delivery systems and theranostics are researched to overcome antibiotic resistance, decrease the side effects of antibiotics, improve the treatment response, and early diagnose. Therefore, in the present study, nanosized, radiolabeled with ^99mTc, colistin encapsulated, neutral and cationic liposome formulations were prepared as the theranostic agent for Pseudomonas aeruginosa infections. Liposomes exhibited appropriate physicochemical properties thanks to their nano-particle size (between 173 and 217 nm), neutral zeta potential value (about - 6.5 and 2.8 mV), as well as encapsulation efficiency of about 75%. All liposome formulations were radiolabeled with over 90% efficiency, and the concentration of stannous chloride was found as 1 mg.mL^-1 to obtain maximum radiolabeling efficiency. In alamar blue analysis, neutral liposome formulations were found more biocompatible compared with the cationic formulations. Neutral colistin encapsulated liposomes were found to be more effective against P. aeruginosa strain according to their time-dependent antibacterial effect, in addition to their highest bacterial binding capacity. As conclusion, theranostic, nanosized, colistin encapsulated, neutral liposome formulations were found as promising agents for the imaging and treating of P. aeruginosa infections.

Emerging strategies in nanotechnology to treat respiratory tract infections: realizing current trends for future clinical perspectives

A boom in respiratory tract infection cases has inflicted a socio-economic burden on the healthcare system worldwide, especially in developing countries. Limited alternative therapeutic options have posed a major threat to human health. Nanotechnology has brought an immense breakthrough in the pharmaceutical industry in a jiffy. The vast applications of nanotechnology ranging from early diagnosis to treatment strategies are employed for respiratory tract infections. The research avenues explored a multitude of nanosystems for effective drug delivery to the target site and combating the issues laid through multidrug resistance and protective niches of the bacteria. In this review a brief introduction to respiratory diseases and multifaceted barriers imposed by bacterial infections are enlightened. The manuscript reviewed different nanosystems, i.e. liposomes, solid lipid nanoparticles, polymeric nanoparticles, dendrimers, nanogels, and metallic (gold and silver) which enhanced bactericidal effects, prevented biofilm formation, improved mucus penetration, and site-specific delivery. Moreover, most of the nanotechnology-based recent research is in a preclinical and clinical experimental stage and safety assessment is still challenging.

Variability of murine bacterial pneumonia models used to evaluate antimicrobial agents

Antimicrobial resistance has become one of the greatest threats to human health, and new antibacterial treatments are urgently needed. As a tool to develop novel therapies, animal models are essential to bridge the gap between preclinical and clinical research. However, despite common usage of in vivo models that mimic clinical infection, translational challenges remain high. Standardization of in vivo models is deemed necessary to improve the robustness and reproducibility of preclinical studies and thus translational research. The European Innovative Medicines Initiative (IMI)-funded “Collaboration for prevention and treatment of MDR bacterial infections” (COMBINE) consortium, aims to develop a standardized, quality-controlled murine pneumonia model for preclinical efficacy testing of novel anti-infective candidates and to improve tools for the translation of preclinical data to the clinic. In this review of murine pneumonia model data published in the last 10 years, we present our findings of considerable variability in the protocols employed for testing the efficacy of antimicrobial compounds using this in vivo model. Based on specific inclusion criteria, fifty-three studies focusing on antimicrobial assessment against Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii were reviewed in detail. The data revealed marked differences in the experimental design of the murine pneumonia models employed in the literature. Notably, several differences were observed in variables that are expected to impact the obtained results, such as the immune status of the animals, the age, infection route and sample processing, highlighting the necessity of a standardized model.

Antimicrobial Activity Enhancers: Towards Smart Delivery of Antimicrobial Agents

The development of effective treatments against infectious diseases is an extensive and ongoing process due to the rapid adaptation of bacteria to antibiotic-based therapies. However, appropriately designed activity enhancers, including antibiotic delivery systems, can increase the effectiveness of current antibiotics, overcoming antimicrobial resistance and decreasing the chance of contributing to further bacterial resistance. The activity/delivery enhancers improve drug absorption, allow targeted antibiotic delivery, improve their tissue and biofilm penetration and reduce side effects. This review provides insights into various antibiotic activity enhancers, including polymer, lipid, and silver-based systems, designed to reduce the adverse effects of antibiotics and improve formulation stability and efficacy against multidrug-resistant bacteria.

Current Advances in Lipid and Polymeric Antimicrobial Peptide Delivery Systems and Coatings for the Prevention and Treatment of Bacterial Infections

Bacterial infections constitute a threat to public health as antibiotics are becoming less effective due to the emergence of antimicrobial resistant strains and biofilm and persister formation. Antimicrobial peptides (AMPs) are considered excellent alternatives to antibiotics; however, they suffer from limitations related to their peptidic nature and possible toxicity. The present review critically evaluates the chemical characteristics and antibacterial effects of lipid and polymeric AMP delivery systems and coatings that offer the promise of enhancing the efficacy of AMPs, reducing their limitations and prolonging their half-life. Unfortunately, the antibacterial activities of these systems and coatings have mainly been evaluated in vitro against planktonic bacteria in less biologically relevant conditions, with only some studies focusing on the antibiofilm activities of the formulated AMPs and on the antibacterial effects in animal models. Further improvements of lipid and polymeric AMP delivery systems and coatings may involve the functionalization of these systems to better target the infections and an analysis of the antibacterial activities in biologically relevant environments. Based on the available data we proposed which polymeric AMP delivery system or coatings could be profitable for the treatment of the different hard-to-treat infections, such as bloodstream infections and catheter- or implant-related infections.

Nanoparticle-mediated pulmonary drug delivery: state of the art towards efficient treatment of recalcitrant respiratory tract bacterial infections

Recalcitrant respiratory tract infections caused by bacteria have emerged as one of the greatest health challenges worldwide. Aerosolized antimicrobial therapy is becoming increasingly attractive to combat such infections, as it allows targeted delivery of high drug concentrations to the infected organ while limiting systemic exposure. However, successful aerosolized antimicrobial therapy is still challenged by the diverse biological barriers in infected lungs. Nanoparticle-mediated pulmonary drug delivery is gaining increasing attention as a means to overcome the biological barriers and accomplish site-specific drug delivery by controlling release of the loaded drug(s) at the target site. With the aim to summarize emerging efforts in combating respiratory tract infections by using nanoparticle-mediated pulmonary delivery strategies, this review provides a brief introduction to the bacterial infection-related pulmonary diseases and the biological barriers for effective treatment of recalcitrant respiratory tract infections. This is followed by a summary of recent advances in design of inhalable nanoparticle-based drug delivery systems that overcome the biological barriers and increase drug bioavailability. Finally, challenges for the translation from exploratory laboratory research to clinical application are also discussed and potential solutions proposed.

Potential application of liposomal nanodevices for non-cancer diseases: an update on design, characterization and biopharmaceutical evaluation

Liposomes, lipid-based vesicular systems, have attracted major interest as a means to improve drug delivery to various organs and tissues in the human body. Recent literature highlights the benefits of liposomes for use as drug delivery systems, including encapsulating of both hydrophobic and hydrophilic cargos, passive and active targeting, enhanced drug bioavailability and therapeutic effects, reduced systemic side effects, improved cargo penetration into the target tissue and triggered contents release. Pioneering work of liposomes researchers led to introduction of long-circulating, ligand-targeted and triggered release liposomes, as well as, liposomes containing nucleic acids and vesicles containing combination of cargos. Altogether, these findings have led to widespread application of liposomes in a plethora of areas from cancer to conditions such as cardiovascular, neurologic, respiratory, skin, autoimmune and eye disorders. There are numerous review articles on the application of liposomes in treatment of cancer, which seems the primary focus, whereas other diseases also benefit from liposome-mediated treatments. Therefore, this article provides an illustrated detailed overview of liposomal formulations, in vitro characterization and their applications in different disorders other than cancer. Challenges and future directions, which must be considered to obtain the most benefit from applications of liposomes in these disorders, are discussed.

Liposomal delivery of CRISPR/Cas9

Liposomes are one of the most widely investigated carriers for CRISPR/Cas9 delivery. The surface properties of liposomal carriers, including the surface charge, PEGylation, and ligand modification can significantly affect the gene silencing efficiency. Three barriers of systemic CRISPR/Cas9 delivery (long blood circulation, efficient tumor penetration, and efficient cellular uptake/endosomal escape) are analyzed on liposomal carriers with different surface charges, PEGylations, and ligand modifications. Cationic formulations dominate CRISPR/Cas9 delivery and neutral formulations also have good performance while anionic formulations are generally not proper for CRISPR/Cas9 delivery. The PEG dilemma (prolonged blood circulation vs. reduced cellular uptake/endosomal escape) and the side effect of repeated PEGylated formulation (accelerated blood clearance) were discussed. Effects of ligand modification on cationic and neutral formulations were analyzed. Finally, we summarized the achievements in liposomal CRISPR/Cas9 delivery, outlined existing problems, and provided some future perspectives. Liposomes are one of the most widely investigated carriers for CRISPR/Cas9 delivery. The surface properties of liposomal carriers, including the surface charge, PEGylation, and ligand modification can significantly affect the gene silencing efficiency. Three barriers of systemic siRNA delivery (long blood circulation, efficient tumor penetration, and efficient cellular uptake/endosomal escape) are analyzed on liposomal carriers with different surface charges, PEGylations, and ligand modifications. Cationic formulations dominate CRISPR/Cas9 delivery and neutral formulations also have good performance while anionic formulations are generally not proper for CRISPR/Cas9 delivery. The PEG dilemma (prolonged blood circulation vs. reduced cellular uptake/endosomal escape) and the side effect of repeated PEGylated formulation (accelerated blood clearance) were discussed. Effects of ligand modification on cationic and neutral formulations were analyzed. Finally, we summarized the achievements in liposomal CRISPR/Cas9 delivery, outlined existing problems, and provided some future perspectives.

Bioinspired Liposomes for Oral Delivery of Colistin to Combat Intracellular Infections by Salmonella enterica

Bacterial invasion into eukaryotic cells and the establishment of intracellular infection has proven to be an effective means of resisting antibiotic action, as anti-infective agents commonly exhibit a poor permeability across the host cell membrane. Encapsulation of anti-infectives into nanoscaled delivery systems, such as liposomes, is shown to result in an enhancement of intracellular delivery. The aim of the current work is, therefore, to formulate colistin, a poorly permeable anti-infective, into liposomes suitable for oral delivery, and to functionalize these carriers with a bacteria-derived invasive moiety to enhance their intracellular delivery. Different combinations of phospholipids and cholesterol are explored to optimize liposomal drug encapsulation and stability in biorelevant media. These liposomes are then surface-functionalized with extracellular adherence protein (Eap), derived from Staphylococcus aureus. Treatment of HEp-2 and Caco-2 cells infected with Salmonella enterica using colistin-containing, Eap-functionalized liposomes resulted in a significant reduction of intracellular bacteria, in comparison to treatment with nonfunctionalized liposomes as well as colistin alone. This indicates that such bio-invasive carriers are able to facilitate intracellular delivery of colistin, as necessary for intracellular anti-infective activity. The developed Eap-functionalized liposomes, therefore, present a promising strategy for improving the therapy of intracellular infections.