A programmable lipid-polymer hybrid nanoparticle system for localized, sustained antibiotic delivery to Gram-positive and Gram-negative bacterial biofilms

Enzyme-responsive nanoparticles: enhancing the ability of endolysins to eradicate Staphylococcus aureus biofilm

Stimuli-responsive nanomaterials show promise in eradicating Staphylococcus aureus biofilm from implants. Peptidoglycan hydrolases (PGHs) are cationic antimicrobials that can be bioengineered to improve the targeting of persisters and drug-resistant bacteria. However, these molecules can be degraded before reaching the target and/or present limited efficacy against biofilm. Therefore, there is an urgent need to improve their potency. Herein, PGH-polyphosphate nanoparticles (PGH-PP NPs) are formed by ionotropic gelation between cationic PGHs and anionic polyphosphate, with the aim of protecting PHGs and delivering them at the target site triggered by alkaline phosphatase (AP) from S. aureus biofilm. Optimized conditions for obtaining M23-PP NPs and GH15-PP NPs are presented. Size, zeta potential, and transmission electron microscopy imaging confirm the nanoscale size. The system demonstrates outstanding performance, as evidenced by a dramatic reduction in PGHs' minimum inhibitory concentration and minimum bactericidal concentration, together with protection against proteolytic effects, storage stability, and cytotoxicity towards the Caco-2 and HeLa cell lines. Time-kill experiments show the great potential of these negatively charged delivery systems in overcoming the staphylococcal biofilm barrier. Efficacy under conditions inhibiting AP proves the enzyme-triggered delivery of PGHs. The enzyme-responsive PGH-PP NPs significantly enhance the effectiveness of PGHs against bacteria residing in biofilm, offering a promising strategy for eradicating S. aureus biofilm.

Liposomal drug delivery strategies to eradicate bacterial biofilms: Challenges, recent advances, and future perspectives

Typical antibiotic treatments are often ineffectual against biofilm-related infections since bacteria residing within biofilms have developed various mechanisms to resist antibiotics. To overcome these limitations, antimicrobial-loaded liposomal nanoparticles are a promising anti-biofilm strategy as they have demonstrated improved antibiotic delivery and eradication of bacteria residing in biofilms. Antibiotic-loaded liposomal nanoparticles revealed remarkably higher antibacterial and anti-biofilm activities than free drugs in experimental settings. Moreover, liposomal nanoparticles can be used efficaciously for the combinational delivery of antibiotics and other antimicrobial compounds/peptide which facilitate, for instance, significant breakdown of the biofilm matrix, increased bacterial elimination from biofilms and depletion of metabolic activity of various pathogens. Drug-loaded liposomes have mitigated recurrent infections and are considered a promising tool to address challenges associated to antibiotic resistance. Furthermore, it has been demonstrated that surface charge and polyethylene glycol modification of liposomes have a notable impact on their antibacterial biofilm activity. Future investigations should tackle the persistent hurdles associated with development of safe and effective liposomes for clinical application and investigate novel antibacterial treatments, including CRISPR-Cas gene editing, natural compounds, phages, and nano-mediated approaches. Herein, we emphasize the significance of liposomes in inhibition and eradication of various bacterial biofilms, their challenges, recent advances, and future perspectives.

Selected strategies to fight pathogenic bacteria

Natural products and analogues are a source of antibacterial drug discovery. Considering drug resistance levels emerging for antibiotics, identification of bacterial metalloenzymes and the synthesis of selective inhibitors are interesting for antibacterial agent development. Peptide nucleic acids are attractive antisense and antigene agents representing a novel strategy to target pathogens due to their unique mechanism of action. Antisense inhibition and development of antisense peptide nucleic acids is a new approach to antibacterial agents. Due to the increased resistance of biofilms to antibiotics, alternative therapeutic options are necessary. To develop antimicrobial strategies, optimised in vitro and in vivo models are needed. In vivo models to study biofilm-related respiratory infections, device-related infections: ventilator-associated pneumonia, tissue-related infections: chronic infection models based on alginate or agar beads, methods to battle biofilm-related infections are discussed. Drug delivery in case of antibacterials often is a serious issue therefore this review includes overview of drug delivery nanosystems.

Organically Modified Mesoporous Silica Nanoparticles against Bacterial Resistance

Bacterial antimicrobial resistance is posed to become a major hazard to global health in the 21st century. An aggravating issue is the stalled antibiotic research pipeline, which requires the development of new therapeutic strategies to combat antibiotic-resistant infections. Nanotechnology has entered into this scenario bringing up the opportunity to use nanocarriers capable of transporting and delivering antimicrobials to the target site, overcoming bacterial resistant barriers. Among them, mesoporous silica nanoparticles (MSNs) are receiving growing attention due to their unique features, including large drug loading capacity, biocompatibility, tunable pore sizes and volumes, and functionalizable silanol-rich surface. This perspective article outlines the recent research advances in the design and development of organically modified MSNs to fight bacterial infections. First, a brief introduction to the different mechanisms of bacterial resistance is presented. Then, we review the recent scientific approaches to engineer multifunctional MSNs conceived as an assembly of inorganic and organic building blocks, against bacterial resistance. These elements include specific ligands to target planktonic bacteria, intracellular bacteria, or bacterial biofilm; stimuli-responsive entities to prevent antimicrobial cargo release before arriving at the target; imaging agents for diagnosis; additional constituents for synergistic combination antimicrobial therapies; and aims to improve the therapeutic outcomes. Finally, this manuscript addresses the current challenges and future perspectives on this hot research area.

Nanotechnology-Based Drug Delivery Systems to Control Bacterial-Biofilm-Associated Lung Infections

Airway mucus dysfunction and impaired immunological defenses are hallmarks of several lung diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary diseases, and are mostly causative factors in bacterial-biofilm-associated respiratory tract infections. Bacteria residing within the biofilm architecture pose a complex challenge in clinical settings due to their increased tolerance to currently available antibiotics and host immune responses, resulting in chronic infections with high recalcitrance and high rates of morbidity and mortality. To address these unmet clinical needs, potential anti-biofilm therapeutic strategies are being developed to effectively control bacterial biofilm. This review focuses on recent advances in the development and application of nanoparticulate drug delivery systems for the treatment of biofilm-associated respiratory tract infections, especially addressing the respiratory barriers of concern for biofilm accessibility and the various types of nanoparticles used to combat biofilms. Understanding the obstacles facing pulmonary drug delivery to bacterial biofilms and nanoparticle-based approaches to combatting biofilm may encourage researchers to explore promising treatment modalities for bacterial-biofilm-associated chronic lung infections.

Using Targeted Nano-Antibiotics to Improve Antibiotic Efficacy against Staphylococcus aureus Infections

The poor bioavailability of antibiotics at infection sites is one of the leading causes of treatment failure and increased bacterial resistance. Therefore, developing novel, non-conventional antibiotic delivery strategies to deal with bacterial pathogens is essential. Here, we investigated the encapsulation of two fluoroquinolones, ciprofloxacin and levofloxacin, into polymer-based nano-carriers (nano-antibiotics), with the goal of increasing their local bioavailability at bacterial infection sites. The formulations were optimized to achieve maximal drug loading. The surfaces of nano-antibiotics were modified with anti-staphylococcal antibodies as ligand molecules to target S. aureus pathogens. The interaction of nano-antibiotics with the bacterial cells was investigated via fluorescent confocal microscopy. Conventional tests (MIC and MBC) were used to examine the antibacterial properties of nano-antibiotic formulations. Simultaneously, a bioluminescence assay model was employed, revealing the rapid and efficient assessment of the antibacterial potency of colloidal systems. In comparison to the free-form antibiotic, the targeted nano-antibiotic exhibited enhanced antimicrobial activity against both the planktonic and biofilm forms of S. aureus. Furthermore, our data suggested that the efficacy of a targeted nano-antibiotic treatment can be influenced by its antibiotic release profile.

Lipid-Coated Hybrid Nanoparticles for Enhanced Bacterial Biofilm Penetration and Antibiofilm Efficacy

Up to 80% of all infections are biofilm-mediated and they are often challenging to treat as the underlying bacterial cells can become 100- to 1000-fold more tolerant toward antibiotics. Antibiotic-loaded nanoparticles have gained traction as a potential drug delivery system to treat biofilm infections. In particular, lipid-coated hybrid nanoparticles (LCHNPs) were investigated on their capability to deliver antibiotics into biofilms. In this study, LCHNPs composed of a poly(lactic-co-glycolic acid) (PLGA) core and dioleoyl-3-trimethylammonium propane (DOTAP) lipid shell were developed and loaded with vancomycin (Van). In vitro antibacterial and antibiofilm tests were performed to evaluate the antimicrobial efficacy of the LCHNPs. LCHNPs were successfully fabricated with high vancomycin encapsulation and loading efficiencies, and exhibited enhanced antibacterial effects against planktonic Staphylococcus aureus USA300 when compared against Free-Van and Van-PLGANPs. When used to treat USA300 biofilms, Van-LCHNPs eradicated up to 99.99% of the underlying biofilm cells, an effect which was not observed for Free-Van and Van-PLGANPs. Finally, we showed that by possessing a robust DOTAP shell, LCHNPs were able to penetrate deeply into the biofilms.

Nanoparticles approach to eradicate bacterial biofilm-related infections: A critical review

Biofilm represents one of the crucial factors for the emergence of multi-drug resistance bacterial infections. The high mortality, morbidity and medical device-related infections are associated with biofilm formation, which requires primarily seek alternative treatment strategies. Recently, nanotechnology has emerged as a promising method for eradicating bacterial biofilm-related infection. The efficacy of nanoparticles (NPs) against bacterial infections interest great attention, and the researches on the subject are rapidly increasing. However, the majority of studies continue to focus on the antimicrobial effects of NPs in vitro, while only a few achieved in vivo and very few registered as clinical trials. The present review aimed to organize the scattered available information regarding NPs approach to eradicate bacterial biofilm-related infections. The current review highlighted the advantages and disadvantages associated with this approach, in addition to the challenges that prevent reaching the clinical applications. It was appeared that the production of NPs either as antimicrobials or as drug carriers requires further investigations to overcome the obstacles associated with their kinetic and biocompatibility.

Recent Advances in the Surface Functionalization of PLGA-Based Nanomedicines

Therapeutics are habitually characterized by short plasma half-lives and little affinity for targeted cells. To overcome these challenges, nanoparticulate systems have entered into the disease arena. Poly(d,l-lactide-co-glycolide) (PLGA) is one of the most relevant biocompatible materials to construct drug nanocarriers. Understanding the physical chemistry of this copolymer and current knowledge of its biological fate will help in engineering efficient PLGA-based nanomedicines. Surface modification of the nanoparticle structure has been proposed as a required functionalization to optimize the performance in biological systems and to localize the PLGA colloid into the site of action. In this review, a background is provided on the properties and biodegradation of the copolymer. Methods to formulate PLGA nanoparticles, as well as their in vitro performance and in vivo fate, are briefly discussed. In addition, a special focus is placed on the analysis of current research in the use of surface modification strategies to engineer PLGA nanoparticles, i.e., PEGylation and the use of PEG alternatives, surfactants and lipids to improve in vitro and in vivo stability and to create hydrophilic shells or stealth protection for the nanoparticle. Finally, an update on the use of ligands to decorate the surface of PLGA nanomedicines is included in the review.

Nanotechnology in combating biofilm: A smart and promising therapeutic strategy

Since the birth of civilization, people have recognized that infectious microbes cause serious and often fatal diseases in humans. One of the most dangerous characteristics of microorganisms is their propensity to form biofilms. It is linked to the development of long-lasting infections and more severe illness. An obstacle to eliminating such intricate structures is their resistance to the drugs now utilized in clinical practice (biofilms). Finding new compounds with anti-biofilm effect is, thus, essential. Infections caused by bacterial biofilms are something that nanotechnology has lately shown promise in treating. More and more studies are being conducted to determine whether nanoparticles (NPs) are useful in the fight against bacterial infections. While there have been a small number of clinical trials, there have been several in vitro outcomes examining the effects of antimicrobial NPs. Nanotechnology provides secure delivery platforms for targeted treatments to combat the wide range of microbial infections caused by biofilms. The increase in pharmaceuticals' bioactive potential is one of the many ways in which nanotechnology has been applied to drug delivery. The current research details the utilization of several nanoparticles in the targeted medication delivery strategy for managing microbial biofilms, including metal and metal oxide nanoparticles, liposomes, micro-, and nanoemulsions, solid lipid nanoparticles, and polymeric nanoparticles. Our understanding of how these nanosystems aid in the fight against biofilms has been expanded through their use.

Nanotechnology for Targeted Detection and Removal of Bacteria: Opportunities and Challenges

The emergence of nanotechnology has created unprecedented hopes for addressing several unmet industrial and clinical issues, including the growing threat so-termed "antibiotic resistance" in medicine. Over the last decade, nanotechnologies have demonstrated promising applications in the identification, discrimination, and removal of a wide range of pathogens. Here, recent insights into the field of bacterial nanotechnology are examined that can substantially improve the fundamental understanding of nanoparticle and bacteria interactions. A wide range of developed nanotechnology-based approaches for bacterial detection and removal together with biofilm eradication are summarized. The challenging effects of nanotechnologies on beneficial bacteria in the human body and environment and the mechanisms of bacterial resistance to nanotherapeutics are also reviewed.

Polymeric membranes for biomedical applications

The rapid development of nanotechnology paved the way for further expansion of polymer chemistry and the fabrication of advanced polymeric membranes. Such modifications allowed enhancing or adding some unique properties, including mechanical strength, excellent biocompatibility, easily controlled degradability, and biological activity. This chapter discusses various applications of polymeric membranes in three significant areas of biomedicine, including tissue engineering, drug delivery systems, and diagnostics. It is intended to highlight here possible ways of improvement the properties of polymeric membranes, by modifying with other polymers, functional groups, compounds, drugs, bioactive components, and nanomaterials.

Lipid-Polymer Hybrid Nanoparticles Enhance the Potency of Ampicillin against Enterococcus faecalis in a Protozoa Infection Model

Enterococcus faecalis (E. faecalis) biofilms are implicated in endocarditis, urinary tract infections, and biliary tract infections. Coupled with E. faecalis internalization into host cells, this opportunistic pathogen poses great challenges to conventional antibiotic therapy. The inability of ampicillin (Amp) to eradicate bacteria hidden in biofilms and intracellular niches greatly reduces its efficacy against complicated E. faecalis infections. To enhance the potency of Amp against different forms of E. faecalis infections, Amp was loaded into Lipid-Polymer hybrid Nanoparticles (LPNs), a highly efficient nano delivery platform consisting of a unique combination of DOTAP lipid shell and PLGA polymeric core. The antibacterial activity of these nanoparticles (Amp-LPNs) was investigated in a protozoa infection model, achieving a much higher multiplicity of infection (MOI) compared with studies using animal phagocytes. A significant reduction of total E. faecalis was observed in all groups receiving 250 μg/mL Amp-LPNs compared with groups receiving the same concentration of free Amp during three different interventions, simulating acute and chronic infections and prophylaxis. In early intervention, no viable E. faecalis was observed after 3 h LPNs treatment whereas free Amp did not clear E. faecalis after 24 h treatment. Amp-LPNs also greatly enhanced the antibacterial activity of Amp at late intervention and boosted the survival rate of protozoa approaching 400%, where no viable protozoa were identified in the free Amp groups at the 40 h postinfection treatment time point. Prophylactic effectiveness with Amp-LPNs at a concentration of 250 μg/mL was exhibited in both bacteria elimination and protozoa survival toward subsequent infections. Using protozoa as a surrogate model for animal phagocytes to study high MOI infections, this study suggests that LPN-formulated antibiotics hold the potential to significantly improve the therapeutic outcome in highly complicated bacterial infections.

Intelligent Nanoparticle-Based Dressings for Bacterial Wound Infections

Conventional wound dressing materials containing free antibiotics for bacterial wound infections are presented with several limitations, that is, lack of controlled and triggered release capabilities, and may often not be adequate to address the complex bacteria microenvironment of such infections. Additionally, the improper usage of antibiotics may also result in the emergence of drug resistant strains. While delivery systems (i.e., nanoparticles) that encapsulate antibiotics may potentially overcome some of these limitations, their therapeutic outcomes are still less than desirable. For example, premature drug release or unintended drug activation may occur, which would greatly reduce treatment efficacy. To address this, responsive nanoparticle-based antimicrobial therapies could be a promising strategy. Such nanoparticles can be functionalized to react to a single stimulus or multi stimulus within the bacteria microenvironment and subsequently elicit a therapeutic response. Such "intelligent" nanoparticles can be designed to respond to the microenvironment, that is, an acidic pH, the presence of specific enzymes, bacterial toxins, etc. or to an external stimulus, for example, light, thermal, etc. These responsive nanoparticles can be further incorporated into wound dressings to better promote wound healing. This review summarizes and highlights the recent progress on such intelligent nanoparticle-based dressings as potential wound dressings for bacteria-infected wounds, along with the current challenges and prospects for these technologies to be successfully translated into the clinic.

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.

Liposome as a delivery system for the treatment of biofilm-mediated infections

Biofilm formation by pathogenic microorganisms has been a tremendous challenge for antimicrobial therapies due to various factors. The biofilm matrix sequesters bacterial cells from the exterior environment and therefore prevents antimicrobial agents from reaching the interior. In addition, biofilm surface extracellular polymeric substances can absorb antimicrobial agents and thus reduce their bioavailability. To conquer these protection mechanisms, liposomes have been developed into a drug delivery system for antimicrobial agents against biofilm-mediated infections. The unique characteristics of liposomes, including versatility for cargoes, target-specificity, nonimmunogenicity, low toxicity, and biofilm matrix-/cell membrane-fusogenicity, remarkably improve the effectiveness of antimicrobial agents and minimize recurrence of infections. This review summarizes current development of liposomal carriers for biofilm therapeutics, presents evidence in their practical applications and discusses their potential limitations.

Nanoparticulate drug-delivery systems for fighting microbial biofilms: from bench to bedside

Biofilms are highly tolerant to antimicrobial agents and adverse environmental conditions being important reservoirs for chronic and hard-to-treat infections. Nanomaterials exhibit microbiostatic/microbicidal/antipathogenic properties and can be also used for the delivery of antibiofilm agents. However, few of the many promising leads offered by nanotechnology reach clinical studies and eventually, become available to clinicians. The aim of this paper was to review the progress and challenges in the development of nanotechnology-based antibiofilm drug-delivery systems. The main identified challenges are: most papers report only in vitro studies of the activity of different nanoformulations; lack of standardization in the methodological approaches; insufficient collaboration between material science specialists and clinicians; paucity of in vivo studies to test efficiency and safety.

Therapeutic lipid-coated hybrid nanoparticles against bacterial infections

One of the most important health concerns in society is the development of pathogen-causing nosocomial infections. Since the first discovery of antibiotics, bacterial infections have been highly treatable. However, with evolution and the nondiscretionary usage of antibiotics, pathogens have also found new ways to survive the onslaught of antibiotics by surviving intracellularly or through the formation of obstinate biofilms, and through these, the outcomes of regular antibiotic treatments may now be unsatisfactory. Lipid-coated hybrid nanoparticles (LCHNPs) are the next-generation core–shell structured nanodelivery system, where an inorganic or organic core, loaded with antimicrobials, is enveloped by lipid layers. This core–shell structure, with multifarious decorations, not only improves the loading capabilities of therapeutics but also has the potential to improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections. Although there has been significant interest in the development of LCHNPs, they have yet to be widely exploited for bacterial infections. In this review, we will provide an overview on the latest development of LCHNPs and the various approaches in synthesizing this nano-delivery system. In addition, a discussion on future perspectives of LCHNPs, in combination with other novel anti-bacterial technologies, will be provided towards the end of this review.

Lipid-coated hybrid nanoparticles are next-generation core–shell structured nanodelivery systems, which improve the loading capabilities of therapeutics and can improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections.

All-in-one NIR-activated nanoplatforms for enhanced bacterial biofilm eradication

The chronic infection of humans by antibiotic-resistant bacteria and their related biofilm have, so far, not been properly addressed. In the present work, we developed a novel antibacterial nanoplatform showing the most efficient antibiotic-resistant bacteria inhibition and biofilm eradication. This particular formulation contains tobramycin-conjugated graphene oxide, for efficiently capturing bacteria through electrostatic interactions and eliminating bacteria as a "nano-knife", and copper sulphide nanoparticles for enhancing the photothermal and photodynamic properties. This novel formulation can selectively eliminate bacteria over NIH 3T3 cells, and the biofilm eradication capacity was up to 70%. Importantly, the nanoplatforms can inhibit bacterial growth and promote the repair of antibiotic-resistant bacteria-infected wounds on rats without non-specific damage to normal tissue. This work provides an effective, simple, and rapid method for the design and fabrication of near-infrared light-induced nanoplatforms that offer possibilities to treat biofilm-related infections.