Antimicrobial efficacy of tobramycin polymeric nanoparticles for Pseudomonas aeruginosa infections in cystic fibrosis: formulation, characterisation and functionalisation with dornase alfa (DNase)

Antibacterial and antifungal impacts of combined silver, zinc oxide, and chitosan nanoparticles within tissue conditioners of complete dentures in vitro

BACKGROUND

Tissue conditioners are suitable places for colonization of microorganisms. A combination of tissue conditioners with antibacterial and antifungal materials inhibits the growth of microorganisms.

AIMS

Here, we aimed to investigate the antibacterial and antifungal effects of silver (Ag), zinc oxide (ZnO), and chitosan nanoparticles on tissue conditioners in complete dentures.

METHODS

The growth of four microorganisms in six different concentrations of Ag, ZnO, and chitosan nanoparticles was investigated after 24 and 48 h. Nanoparticles were synthesized using optical sequestration and approved by scanning electron microscope, x-ray diffraction, and infrared (FT-IR) methods. Nanoparticles were combined at 0.5, 0.25, and 0.25 ratios (chitosan, Ag, and ZnO, respectively) with 0.625, 1.25, 2.5, 5, 10, and 20 mass percentages. Tissue conditioners with nanoparticles were entered to test tubes containing microorganisms, and the growth rate was measured using the turbidity method by spectrophotometer after 24 and 48 h of incubation at 37 °C.

RESULTS

Growth inhibition of Candida albicans occurred at 2.5% concentration. However, the growth inhibition of Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa occurred at 5% after both 24 and 48 h. Also, the optimum nanoparticle concentration for Candida albicans was found to be 1.25% for both timings. On the other hand, the optimum nanoparticle concentration for Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa was 2.5% for both time scales.

CONCLUSIONS

The combination of Ag, ZnO, and chitosan nanoparticles inhibited the growth of fungi and bacteria in tissue conditioners. These nanoparticles inhibited the growth of fungi more effectively than bacteria.

Polymyxin Delivery Systems: Recent Advances and Challenges

Polymyxins are vital antibiotics for the treatment of multiresistant Gram-negative ESKAPE pathogen infections. However, their clinical value is limited by their high nephrotoxicity and neurotoxicity, as well as their poor permeability and absorption in the gastrointestinal tract. This review focuses on various polymyxin delivery systems that improve polymyxin bioavailability and reduce drug toxicity through targeted and controlled release. Currently, the most suitable systems for improving oral, inhalation, and parenteral polymyxin delivery are polymer particles, liposomes, and conjugates, while gels, polymer fibers, and membranes are attractive materials for topical administration of polymyxin for the treatment of infected wounds and burns. In general, the application of these systems protects polymyxin molecules from the negative effects of both physiological and pathological factors while achieving higher concentrations at the target site and reducing dosage and toxicity. Improving the properties of polymyxin will be of great interest to researchers who are focused on developing antimicrobial drugs that show increased efficacy and safety.

Nano-Based Drug Delivery or Targeting to Eradicate Bacteria for Infection Mitigation: A Review of Recent Advances

Pathogenic bacteria infection is a major public health problem due to the high morbidity and mortality rates, as well as the increased expenditure on patient management. Although there are several options for antimicrobial therapy, their efficacy is limited because of the occurrence of drug-resistant bacteria. Many conventional antibiotics have failed to show significant amelioration in overall survival of infectious patients. Nanomedicine for delivering antibiotics provides an opportunity to improve the efficiency of the antibacterial regimen. Nanosystems used for antibiotic delivery and targeting to infection sites render some benefits over conventional formulations, including increased solubility, enhanced stability, improved epithelium permeability and bioavailability, prolonged antibiotic half-life, tissue targeting, and minimal adverse effects. The nanocarriers' sophisticated material engineering tailors the controllable physicochemical properties of the nanoparticles for bacterial targeting through passive or active targeting. In this review, we highlight the recent progress on the development of antibacterial nanoparticles loaded with antibiotics. We systematically introduce the concepts and amelioration mechanisms of the nanomedical techniques for bacterial eradication. Passive targeting by modulating the nanoparticle structure and the physicochemical properties is an option for efficient drug delivery to the bacteria. In addition, active targeting, such as magnetic hyperthermia induced by iron oxide nanoparticles, is another efficient way to deliver the drugs to the targeted site. The nanoparticles are also designed to respond to the change in environment pH or enzymes to trigger the release of the antibiotics. This article offers an overview of the benefits of antibacterial nanosystems for treating infectious diseases.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

Novel drug delivery systems and significance in respiratory diseases

Pulmonary drug delivery offers targeted therapy for the treatment of respiratory diseases such as asthma, lung cancer, and chronic obstructive pulmonary diseases. However, this route poses challenges like deposition mechanism, drug instability, and rapid clearance mechanism. Other factors like the type of inhaler device, patient compatibility, consistent delivery by device, and inhaler technique also affect the performance of pulmonary delivery systems. Thus, to overcome these issues, pulmonary delivery systems utilizing particle-based approaches (nano/microparticles) have emerged in the last two decades. This chapter provides insight into various mechanisms of pulmonary drug administration, the ideal requirements of a pulmonary system, and the general devices used for pulmonary delivery. An overview of new pulmonary delivery systems and their relevance in the treatment of respiratory diseases is provided. In the end, novel pulmonary technologies that have been patented and cleared clinical trials have been highlighted along with the advances in the inhaler device.

Novel Therapeutic Strategies Applied to Pseudomonas aeruginosa Infections in Cystic Fibrosis

Cystic fibrosis (CF) is one of the most prevalent genetic diseases and a total of 1700 different genetic mutations can cause this condition. Patients that suffer this disease have a thickening of the mucus, creating an environment that promotes bacterial infections. Pseudomonas aeruginosa is a ubiquitous bacterium, which is frequently found in the lungs of CF patients. P. aeruginosa is known for its high level of antibiotic resistance as well as its high rate of mutation that allows it to rapidly evolve and adapt to a multitude of conditions. When a CF lung is infected with P. aeruginosa, the decay of the patient is accelerated, but there is little that can be done apart from controlling the infection with antibiotics. Novel strategies to control P. aeruginosa infection are imperative, and nanotechnology provides novel approaches to drug delivery that are more efficient than classic antibiotic treatments. These drug delivery systems are offering new prospects, especially for these patients with special mucus conditions and bacterial characteristics that limit antibiotic use.

Targeted delivery of antibiotics to the infected pulmonary tissues using ROS-responsive nanoparticles

Background

Immunocompromised individuals and those with lung dysfunction readily acquire pulmonary bacterial infections, which may cause serious diseases and carry a heavy economic burden. Maintaining adequate antibiotic concentrations in the infected tissues is necessary to eradicate resident bacteria. To specifically deliver therapeutics to the infected pulmonary tissues and enable controlled release of payloads at the infection site, a ROS-responsive material, i.e. 4-(hydroxymethyl) phenylboronic acid pinacol ester-modified α-cyclodextrin (Oxi-αCD), was employed to encapsulate moxifloxacin (MXF), generating ROS-responsive MXF-containing nanoparticles (MXF/Oxi-αCD NPs).

Results

MXF/Oxi-αCD NPs were coated with DSPE-PEG and DSPE-PEG-folic acid, facilitating penetration of the sputum secreted by the infected lung and enabling the active targeting of macrophages in the inflammatory tissues. In vitro drug release experiments indicated that MXF release from Oxi-αCD NPs was accelerated in the presence of 0.5 mM H₂O₂. In vitro assay with Pseudomonas aeruginosa demonstrated that MXF/Oxi-αCD NPs exhibited higher antibacterial activity than MXF. In vitro cellular study also indicated that folic acid-modified MXF/Oxi-αCD NPs could be effectively internalized by bacteria-infected macrophages, thereby significantly eradicating resident bacteria in macrophages compared to non-targeted MXF/Oxi-αCD NPs. In a mouse model of pulmonary P. aeruginosa infection, folic acid-modified MXF/Oxi-αCD NPs showed better antibacterial efficacy than MXF and non-targeted MXF/Oxi-αCD NPs. Meanwhile, the survival time of mice was prolonged by treatment with targeting MXF/Oxi-αCD NPs.

Conclusions

Our work provides a strategy to overcome the mucus barrier, control drug release, and improve the targeting capability of NPs for the treatment of pulmonary bacterial infections.

Challenges and strategies in drug delivery systems for treatment of pulmonary infections

Inhalation therapy has been reported as the most effective treatment for respiratory bacterial infections due to the increasing relevance of drug bioavailability. Drug delivery systems (DDS) have the capacity to overcome pulmonary biological barriers limiting the bioavailability of inhaled anti-infectives. This is important to eradicate bacterial infections and to prevent the development of bacterial resistance. Despite substantial efforts in the field, the current state-of-the-art often fails to achieve those goals, and we still observe increasing bacterial resistance. We give a brief insight on benefits and challenges in pulmonary delivery of anti-infectives. In the context of drug delivery development for pulmonary infections, particularly focusing on Pseudomonas aeruginosa (PA) infections, this mini review will critically discuss the main requirements, as well as the recent strategies of drug delivery system synthesis and preparation. Finally, interaction of DDS with crucial pulmonary biological barriers will be of great importance for the success of future applications of the developed DDS.

Atmospheric pressure non-thermal plasma exposure reduces Pseudomonas aeruginosa lipopolysaccharide toxicity in vitro and in vivo

Lipopolysaccharide (LPS) is an endotoxin composed of a polysaccharide and lipid component. It is intrinsically responsible for the pathogenicity of Gram-negative bacteria and is involved in the development of bacterial sepsis. Atmospheric pressure non-thermal plasma is proposed as a potential new approach for the treatment of infected tissue such as chronic wounds, with both antibacterial and wound-healing activities extensively described. Using both the RAW264.7 murine macrophage cell line in vitro assays and the Galleria mellonella insect in vivo toxicity model, the effect non-thermal plasma exposure on LPS-mediated toxicity has been characterised. Short (60 s) non-thermal plasma exposures of Pseudomonas aeruginosa conditioned growth media, membrane lysates and purified P. aeruginosa LPS, resulted in a substantial detoxification and reduction of LPS-induced cytotoxicity in RAW264.7 murine macrophages. Non-thermal plasma exposure (60 s) of purified P. aeruginosa LPS led to a significant (p < 0.05) improvement in the G. mellonella health index (GHI) score, a measure of in vivo toxicity. These findings demonstrate the ability of short plasma exposures to significantly reduce LPS-induced cytotoxicity both in vitro and in vivo; attenuating the toxicity of this important virulence factor intrinsic to the pathogenicity of Gram-negative bacteria.

Nanometric ion pair complexes of tobramycin forming microparticles for the treatment of Pseudomonas aeruginosa infections in cystic fibrosis

Sustained pulmonary delivery of tobramycin from microparticles composed of drug/polymer nanocomplexes offers several advantages against traditional delivery methods. Namely, in patients with cystic fibrosis, microparticle delivery can protect the tobramycin being delivered from strong mucoadhesive interactions, thus avoiding effects on its diffusion toward the infection site. Polymeric ion-pair complexes were obtained starting from two synthetic polyanions, through impregnation of their solid dissociated forms with tobramycin in aqueous solution. The structure of these polymeric systems was characterized, and their activities were examined against various biofilm-forming Pseudomonas aeruginosa. Once dried, the nanocomplexes can change their aggregation state, to form microparticle-based aggregates with a spherical shape and a micrometer size. In aqueous dispersions, the ion-pair complexes produced had nanometric size, negative ζ potential, and high biocompatibility toward human bronchial epithelium cells. The antibiofilm activity of these formulations was more efficient than for free tobramycin, with the antibiofilm activity against P. aeruginosa mucoid and nonmucoid end-stage strains isolated from cystic fibrosis lungs being of particular relevance.

Antimicrobial biopolymer formation from sodium alginate and algae extract using aminoglycosides

Antimicrobial biopolymers provide a biodegradable, sustainable, safe, and cheap approach to drug delivery and wound dressing to control bacterial infection and improve wound healing respectively. Here, we report a one-step method of making antimicrobial alginate polymer from sodium alginate and aqueous extract of Wakame using antibiotic aminoglycosides. Thin layer chromatography of commercially available sodium alginate and Wakame extract showed similar oligosaccharide profiles. Screening of six aminoglycosides showed that kanamycin disulfate and neomycin sulfate produces the highest amount of biopolymer; however, kanamycin disulfate produces the most malleable and form fitting biopolymer. Image texture analysis of biopolymers showed similar quantification parameters for all the six aminoglycosides. Weight of alginate polymer as a function of aminoglycoside concentration follows a growth model of prion protein, consistent with the aggregating nature of both processes. Slow release of antibiotics and the resulting zone of inhibition against E. coli DH5α were observed by agar well diffusion assay. Inexpensive method of production and slow release of antibiotics will enable diverse applications of antimicrobial alginate biopolymer reported in this paper.

Novel cystamine-core dendrimer-formulation rescues ΔF508-CFTR and inhibits Pseudomonas aeruginosa infection by augmenting autophagy

BACKGROUND

Cystic fibrosis (CF) is challenged with pathophysiological barriers for effective airway drug-delivery. Hence, we standardized the therapeutic efficacy of the novel dendrimer-based autophagy-inducing anti-oxidant drug, cysteamine.

RESEARCH DESIGN AND METHODS

Human primary-CF epithelial-cells, CFBE41o-cells were used to standardize the efficacy of the dendrimer-cystamine in correcting impaired-autophagy, rescuing ΔF508-CFTR and Pseudomonas-aeruginosa (Pa) infection.

RESULTS

We first designed a novel cystamine-core dendrimer formulation (G4-CYS) that significantly increases membrane-ΔF508CFTR expression in CFBE41o-cells (p < 0.05) by forming its reduced-form cysteamine, in vivo. Additionally, G4-CYS treatment corrects ΔF508-CFTR-mediated impaired-autophagy as observed by a significant decrease (p < 0.05) in Ub-LC3-positive aggresome-bodies. Next, we verified that in non-permeabilized CFBE41o-cells, G4-CYS significantly (p < 0.05) induces ΔF508-CFTR's forward-trafficking to the plasma membrane. Furthermore, cysteamine's known antibacterial and anti-biofilm properties against Pa were enhanced as our findings demonstrate that both G4-CYS and its control DAB-core dendrimer, G4-DAB, exhibited significant (p < 0.05) bactericidal-activity against Pa. We also found that both G4-CYS and G4-DAB exhibit marked mucolytic-activity against porcine-mucus (p < 0.05). Finally, we demonstrate that G4-CYS not only corrects the autophagy-impairment by rescuing ΔF508-CFTR in CFBE41o-cells but also corrects the intrinsic phagocytosis defect (p < 0.05).

CONCLUSIONS

Overall, our data demonstrates the efficacy of novel cystamine-dendrimer formulation in rescuing ΔF508-CFTR to the plasma membrane and inhibiting Pa bacterial-infection by augmenting autophagy.

Nanomedicine for Cystic Fibrosis

Cystic fibrosis is a genetic disease affecting more than 70,000 people worldwide. Caused by a mutation in the CFTR gene, cystic fibrosis can result in difficulty breathing, widespread bacterial infections, edema, malnutrition, pancreatitis, and death. Current drug-based treatments struggle to reach the site of action due to the thick mucus, and only manage symptoms such as blocked airways, lung infections, and limited ability to digest food. Nanotechnology opens up possibilities for improved treatment strategies by focusing on drug penetration through the mucus lining, eliminating resulting bacterial infections, and targeting the underlying genetic cause of the disease. In this review, we present recent nanoparticle developments for cystic fibrosis, challenges in nanomedicine therapeutics, and future research directions in gene editing and nonviral vectors for gene delivery.

Promising Chitosan-Coated Alginate-Tween 80 Nanoparticles as Rifampicin Coadministered Ascorbic Acid Delivery Carrier Against Mycobacterium tuberculosis

The aim of this study was to design a nanocarrier system for inhalation delivery of rifampicin (RIF) in combination with ascorbic acid (ASC), namely constituted of sodium alginate coated with chitosan and Tween 80 (RIF/ASC NPs) as a platform for the treatment of pulmonary tuberculosis infection. A Box-Behnken experimental design and response surface methodology (RSM) were applied to elucidate and evaluate the effects of several factors on the nanoparticle properties. On the other hand, it was found that RIF/ASC NPs were less cytotoxic than the free RIF, showing a significantly improved activity against nine clinical strains of Mycobacterium tuberculosis (M. tb) in comparison with the free drug. RIF/ASC NPs had an average particle size of 324.0 ± 40.7 nm, a polydispersity index of 0.226 ± 0.030, and a zeta potential of - 28.52 ± 0.47 mV and the surface was hydrophilic. The addition of sucrose (1% w/v) to the nanosuspension resulted in the formation of a solid pellet easily redispersible after lyophilization. RIF/ASC NPs were found to be stable at different physiological pH values. In summary, findings of this work highlight the potential of the RIF/ASC NP-based formulation development herein to deliver RIF in combination with ASC through pulmonary route by exploring a non-invasive route of administration of this antibiotic, increasing the local drug concentrations in lung tissues, the primary infection site, as well as reducing the risk of systemic toxicity and hence improving the patient compliance.

Alginate Nanoparticles for Drug Delivery and Targeting

Nanotechnology refers to the control, manipulation, study and manufacture of structures and devices at the nanometer size range. The small size, customized surface, improved solubility and multi-functionality of nanoparticles will continue to create new biomedical applications, as nanoparticles allow to dominate stability, solubility and bioavailability, as well controlled release of drugs. The type of a nanoparticle, and its related chemical, physical and morphological properties influence its interaction with living cells, as well as determine the route of clearance and possible toxic effects. This field requires cross-disciplinary research and gives opportunities to design and develop multifunctional devices, which allow the diagnosis and treatment of devastating diseases. Over the past few decades, biodegradable polymers have been studied for the fabrication of drug delivery systems. There was extensive development of biodegradable polymeric nanoparticles for drug delivery and tissue engineering, in view of their applications in controlling the release of drugs, stabilizing labile molecules from degradation and site-specific drug targeting. The primary aim is to reduce dosing frequency and prolong the therapeutic outcomes. For this purpose, inert excipients should be selected, being biopolymers, e.g. sodium alginate, commonly used in controlled drug delivery. Nanoparticles composed of alginate (known as anionic polysaccharide widely distributed in the cell walls of brown algae which, when in contact with water, forms a viscous gum) have emerged as one of the most extensively characterized biomaterials used for drug delivery and targeting a set of administration routes. Their advantages include not only the versatile physicochemical properties, which allow chemical modifications for site-specific targeting but also their biocompatibility and biodegradation profiles, as well as mucoadhesiveness. Furthermore, mechanical strength, gelation, and cell affinity can be modulated by combining alginate nanoparticles with other polymers, surface tailoring using specific targeting moieties and by chemical or physical cross-linking. However, for every physicochemical modification in the macromolecule/ nanoparticles, a new toxicological profile may be obtained. In this paper, the different aspects related to the use of alginate nanoparticles for drug delivery and targeting have been revised, as well as how their toxicological profile will determine the therapeutic outcome of the drug delivery system.

Standardization of G. mellonella Larvae to Provide Reliable and Reproducible Results in the Study of Fungal Pathogens

In the past decade, Galleria mellonella (wax moth) larvae have become widely used as a non-mammalian infection model. However, the full potential of this infection model has yet to be realised, limited by the variable quality of larvae used and the lack of standardised procedures. Here, we review larvae suitable for research, protocols for dosing larvae, and methods for scoring illness in larvae infected with fungal pathogens. The development of standardised protocols for carrying out our experimental work will allow high throughput screens to be developed, changing the way in which we evaluate panels of mutants and strains. It will also enable the in vivo screening of potential antimicrobials at an earlier stage in the research and development cycle.

Nanodelivery strategies for the treatment of multidrug-resistant bacterial infections

One of the most important health concerns in society is the development of nosocomial infections caused by multidrug-resistant pathogens. The purpose of this review is to discuss the issues in current antibiotic therapies and the ongoing progress of developing new strategies for the treatment of ESKAPE pathogen infections, which is acronymized for Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species. We not only examine the current issues caused by multidrug resistance but we also examine the barrier effects such as biofilm and intracellular localization exploited by these pathogens to avoid antibiotic exposure. Recent innovations in nanomedicine approaches and antibody antibiotic conjugates are reviewed as potential novel approaches for the treatment of bacterial infection, which ultimately may expand the useful life span of current antibiotics.

Cold Plasmas for Biofilm Control: Opportunities and Challenges

Bacterial biofilm infections account for a major proportion of chronic and medical device associated infections in humans, yet our ability to control them is compromised by their inherent tolerance to antimicrobial agents. Cold atmospheric plasma (CAP) represents a promising therapeutic option. CAP treatment of microbial biofilms represents the convergence of two complex phenomena: the production of a chemically diverse mixture of reactive species and intermediates, and their interaction with a heterogeneous 3D interface created by the biofilm extracellular polymeric matrix. Therefore, understanding these interactions and physiological responses to CAP exposure are central to effective management of infectious biofilms. We review the unique opportunities and challenges for translating CAP to the management of biofilms.

Clearance of intracellular Klebsiella pneumoniae infection using gentamicin-loaded nanoparticles

Klebsiella pneumoniae is a foremost gram-negative pathogen that can induce life-threatening nosocomial pulmonary infections. Although it can be phagocytosed successfully by lung resident macrophages, this pathogen remains viable within vacuolar compartments, resulting in chronic infection and limiting therapeutic treatment with antibiotics. In this study, we aimed to generate and evaluate a cell-penetrant antibiotic poly(lactide-co-glycolide) (PLGA)-based formulation that could successfully treat intracellular K. pneumoniae infection. Screening of formulation conditions allowed the generation of high drug loaded nanoparticles through a water-in-oil-in-water approach. We demonstrated the therapeutic usefulness of these gentamicin-loaded nanoparticles (GNPs), showing their ability to improve survival and provide extended prophylactic protection towards K. pneumoniae using a Galleria mellonella infection model. We subsequently showed that the GNPs could be phagocytosed by K. pneumoniae infected macrophages, and significantly reduce the viability of the intracellular bacteria without further stimulation of pro-inflammatory or pro-apoptotic effects on the macrophages. Taken together, these results clearly show the potential to use antibiotic loaded NPs to treat intracellular K. pneumoniae infection, reducing bacterial viability without concomitant stimulation of inflammatory or pyroptotic pathways in the treated cells.

Starch-Chitosan Polyplexes: A Versatile Carrier System for Anti-Infectives and Gene Delivery

Despite the enormous potential of nanomedicine, the search for materials from renewable resources that balance bio-medical requirements and engineering aspects is still challenging. This study proposes an easy method to make nanoparticles composed of oxidized starch and chitosan, both isolated from natural biopolymers. The careful adjustment of C/N ratio, polymer concentration and molecular weight allowed for tuning of particle characteristics. The system's carrier capability was assessed both for anti-infectives and for nucleic acid. Higher starch content polyplexes were found to be suitable for high encapsulation efficiency of cationic anti-infectives and preserving their bactericidal function. A cationic carrier was obtained by coating the anionic polyplex with chitosan. Coating allowed for a minimal amount of cationic polymer to be employed and facilitated plasmid DNA loading both within the particle core and on the surface. Transfection studies showed encouraging result, approximately 5% of A549 cells with reporter gene expression. In summary, starch-chitosan complexes are suitable carriers with promising perspectives for pharmaceutical use.

New Perspectives in Biofilm Eradication

Microbial biofilms, which are elaborate and highly resistant microbial aggregates formed on surfaces or medical devices, cause two-thirds of infections and constitute a serious threat to public health. Immunocompromised patients, individuals who require implanted devices, artificial limbs, organ transplants, or external life support and those with major injuries or burns, are particularly prone to become infected. Antibiotics, the mainstay treatments of bacterial infections, have often proven ineffective in the fight against microbes when growing as biofilms, and to date, no antibiotic has been developed for use against biofilm infections. Antibiotic resistance is rising, but biofilm-mediated multidrug resistance transcends this in being adaptive and broad spectrum and dependent on the biofilm growth state of organisms. Therefore, the treatment of biofilms requires drug developers to start thinking outside the constricted "antibiotics" box and to find alternative ways to target biofilm infections. Here, we highlight recent approaches for combating biofilms focusing on the eradication of preformed biofilms, including electrochemical methods, promising antibiofilm compounds and the recent progress in drug delivery strategies to enhance the bioavailability and potency of antibiofilm agents.

From Nano to Micro: using nanotechnology to combat microorganisms and their multidrug resistance

The spread of antibiotic resistance and increasing prevalence of biofilm-associated infections is driving demand for new means to treat bacterial infection. Nanotechnology provides an innovative platform for addressing this challenge, with potential to manage even infections involving multidrug-resistant (MDR) bacteria. The current review summarizes recent progress over the last 2 years in the field of antibacterial nanodrugs, and describes their unique properties, mode of action and activity against MDR bacteria and biofilms. Biocompatibility and commercialization are also discussed. As opposed to the more common division of nanoparticles (NPs) into organic- and inorganic-based materials, this review classifies NPs into two functional categories. The first includes NPs exhibiting intrinsic antibacterial properties and the second is devoted to NPs serving as a cargo for delivering antibacterial agents. Antibacterial nanomaterials used to decorate medical devices and implants are reviewed here as well.

Efficacy and safety concerns over the use of mucus modulating agents for drug delivery using nanoscale systems

Drug delivery to the mucus covered mucosae is fraught with difficulties and many different approaches have been developed to permeate the mucus barrier. Generally by modifying the delivery system to avoid interaction with the mucus. These modifications are reviewed here in terms of efficacy and safety. These are particular problems for oral delivery the pharmaceutical industry's favoured route for drug administration. For effective delivery through the gastrointestinal tract a drug must pass through three barriers in sufficient amounts to yield a biological effect. These barriers are the digestive barrier in the lumen, the mucus barrier, and the epithelial barrier. Other approaches involve mucolytic agents added with or prior to the delivery system or agents regulating mucus production and are reviewed here. In terms of safety, a key property of a mucus modulating delivery system is that it must not damage the protective function of the mucus layer.

The role of mucus on drug transport and its potential to affect therapeutic outcomes

A layer of mucus covers the surface of all wet epithelia throughout the human body. Mucus is a hydrogel mainly composed of water, mucins (glycoproteins), DNA, proteins, lipids, and cell debris. This complex composition yields a tenacious viscoelastic hydrogel that lubricates and protects the exposed epithelia from external threats and enzymatic degradation. The natural protective role of mucus is nowadays acknowledged as a major barrier to be overcome in non-invasive drug delivery. The heterogeneity of mucus components offers a wide range of potential chemical interaction sites for macromolecules, while the mesh-like architecture given to mucus by the intermolecular cross-linking of mucin molecules results in a dense network that physically, and in a size-dependent manner, hinders the diffusion of nanoparticles through mucus. Consequently, drug diffusion, epithelial absorption, drug bioavailability, and ultimately therapeutic outcomes of mucosal drug delivery can be attenuated.

Targeting microbial biofilms: current and prospective therapeutic strategies

Biofilm formation is a key virulence factor for a wide range of microorganisms that cause chronic infections. The multifactorial nature of biofilm development and drug tolerance imposes great challenges for the use of conventional antimicrobials and indicates the need for multi-targeted or combinatorial therapies. In this Review, we focus on current therapeutic strategies and those under development that target vital structural and functional traits of microbial biofilms and drug tolerance mechanisms, including the extracellular matrix and dormant cells. We emphasize strategies that are supported by in vivo or ex vivo studies, highlight emerging biofilm-targeting technologies and provide a rationale for multi-targeted therapies aimed at disrupting the complex biofilm microenvironment.

Dendrimer-based selective autophagy-induction rescues ΔF508-CFTR and inhibits Pseudomonas aeruginosa infection in cystic fibrosis

Background

Cystic Fibrosis (CF) is a genetic disorder caused by mutation(s) in the CF-transmembrane conductance regulator (Cftr) gene. The most common mutation, ΔF508, leads to accumulation of defective-CFTR protein in aggresome-bodies. Additionally, Pseudomonas aeruginosa (Pa), a common CF pathogen, exacerbates obstructive CF lung pathology. In the present study, we aimed to develop and test a novel strategy to improve the bioavailability and potentially achieve targeted drug delivery of cysteamine, a potent autophagy-inducing drug with anti-bacterial properties, by developing a dendrimer (PAMAM-DEN)-based cysteamine analogue.

Results

We first evaluated the effect of dendrimer-based cysteamine analogue (PAMAM-DEN^CYS) on the intrinsic autophagy response in IB3-1 cells and observed a significant reduction in Ub-RFP and LC3-GFP co-localization (aggresome-bodies) by PAMAM-DEN^CYS treatment as compared to plain dendrimer (PAMAM-DEN) control. Next, we observed that PAMAM-DEN^CYS treatment shows a modest rescue of ΔF508-CFTR as the C-form. Moreover, immunofluorescence microscopy of HEK-293 cells transfected with ΔF508-CFTR-GFP showed that PAMAM-DEN^CYS is able to rescue the misfolded-ΔF508-CFTR from aggresome-bodies by inducing its trafficking to the plasma membrane. We further verified these results by flow cytometry and observed significant (p<0.05; PAMAM-DEN vs. PAMAM-DEN^CYS) rescue of membrane-ΔF508-CFTR with PAMAM-DEN^CYS treatment using non-permeabilized IB3-1 cells immunostained for CFTR. Finally, we assessed the autophagy-mediated bacterial clearance potential of PAMAM-DEN^CYS by treating IB3-1 cells infected with PA01-GFP, and observed a significant (p<0.01; PAMAM-DEN vs. PAMAM-DEN^CYS) decrease in intracellular bacterial counts by immunofluorescence microscopy and flow cytometry. Also, PAMAM-DEN^CYS treatment significantly inhibits the growth of PA01-GFP bacteria and demonstrates potent mucolytic properties.

Conclusions

We demonstrate here the efficacy of dendrimer-based autophagy-induction in preventing sequestration of ΔF508-CFTR to aggresome-bodies while promoting its trafficking to the plasma membrane. Moreover, PAMAM-DEN^CYS decreases Pa infection and growth, while showing mucolytic properties, suggesting its potential in rescuing Pa-induced ΔF508-CF lung disease that warrants further investigation in CF murine model.

A highly adhesive and naturally derived sealant

Conventional surgical techniques to seal and repair defects in highly stressed elastic tissues are insufficient. Therefore, this study aimed to engineer an inexpensive, highly adhesive, biocompatible, and biodegradable sealant based on a modified and naturally derived biopolymer, gelatin methacryloyl (GelMA). We tuned the degree of gelatin modification, prepolymer concentration, photoinitiator concentration, and crosslinking conditions to optimize the physical properties and adhesion of the photocrosslinked GelMA sealants. Following ASTM standard tests that target wound closure strength, shear resistance, and burst pressure, GelMA sealant was shown to exhibit adhesive properties that were superior to clinically used fibrin- and poly(ethylene glycol)-based glues. Chronic in vivo experiments in small as well as translational large animal models proved GelMA to effectively seal large lung leakages without the need for sutures or staples, presenting improved performance as compared to fibrin glue, poly(ethylene glycol) glue and sutures only. Furthermore, high biocompatibility of GelMA sealant was observed, as evidenced by a low inflammatory host response and fast in vivo degradation while allowing for adequate wound healing at the same time. Combining these results with the low costs, ease of synthesis and application of the material, GelMA sealant is envisioned to be commercialized not only as a sealant to stop air leakages, but also as a biocompatible and biodegradable hydrogel to support lung tissue regeneration.

Free and Nanoencapsulated Tobramycin: Effects on Planktonic and Biofilm Forms of Pseudomonas

Cystic fibrosis (CF) is a genetic disorder in which frequent pulmonary infections develop secondarily. One of the major pulmonary pathogens colonizing the respiratory tract of CF patients and causing chronic airway infections is Pseudomonasaeruginosa. Although tobramycin was initially effective against P. aeruginosa, tobramycin-resistant strains have emerged. Among the strategies for overcoming resistance to tobramycin and other antibiotics is encapsulation of the drugs in nanoparticles. In this study, we explored the antimicrobial activity of nanoencapsulated tobramycin, both in solid lipid nanoparticles (SLN) and in nanostructured lipid carriers (NLC), against clinical isolates of P. aeruginosa obtained from CF patients. We also investigated the efficacy of these formulations in biofilm eradication. In both experiments, the activities of SLN and NLC were compared with that of free tobramycin. The susceptibility of planktonic bacteria was determined using the broth microdilution method and by plotting bacterial growth. The minimal biofilm eradication concentration (MBEC) was determined to assess the efficacy of the different tobramycin formulations against biofilms. The activity of tobramycin-loaded SLN was less than that of either tobramycin-loaded NLC or free tobramycin. The minimum inhibitory concentration (MIC) and MBEC of nanoencapsulated tobramycin were slightly lower (1–2 logs) than the corresponding values of the free drug when determined in tobramycin-susceptible isolates. However, in tobramycin-resistant strains, the MIC and MBEC did not differ between either encapsulated form and free tobramycin. Our results demonstrate the efficacy of nanoencapsulated formulations in killing susceptible P. aeruginosa from CF and from other patients.

Biofunctionalization of surfaces using polyelectrolyte multilayers

Biomaterials play a central role in modern strategies in regenerative medicine and tissue engineering to restore the structure and function of damaged or dysfunctional tissue and to direct cellular behavior. Both biologically derived and synthetic materials have been extensively explored in this context. However, most materials when implanted into living tissue initiate a host response. Modern implant design therefore aims to improve implant integration while avoiding chronic inflammation and foreign body reactions, and thus loss of the intended implant function. Directing these processes requires an in-depth understanding of the immunological processes that take place at the interface between biomaterials and the host tissue. The physicochemical properties of biomaterial surfaces (charge, charge density, hydrophilicity, functional molecular domains, etc.) are decisive, as are their stiffness, roughness and topography. This review outlines specific strategies, using polyelectrolyte multilayers to modulate the interactions between biomaterial surfaces and biological systems. The described coatings have the potential to control the adhesion of proteins, bacteria and mammalian cells. They can be used to decrease the risk of bacterial infections occurring after implantation and to achieve better contact between biological tissue and implants. In summary, these results are important for further development and modification of surfaces from different medical implants.

Energy-triggered drug release from polymer nanoparticles for orthopedic applications

Sequestra, present in many cancers and orthopedic infections, provide a safe harbor for the development of drug resistance. In the face of burgeoning drug resistance, the importance of nanoscale, microenvironment-triggered drug delivery cannot be overestimated. Such strategies may preserve pharmaceutical efficacy and significantly alter the etiology of many orthopedic diseases. Although temperature-, pH- and redox-responsive nanoparticle-based systems have been extensively studied, local drug delivery from polymeric nanoparticles can be triggered by a variety of energy forms. This review offers an overview of the state of the field as well as a perspective on the safety and efficacy of ultrasound, hyperthermia and radio frequency-triggered internal delivery systems in a variety of applications.

Polymeric nanoparticles in development for treatment of pulmonary infectious diseases

Serious lung infections, such as pneumonia, tuberculosis, and chronic obstructive cystic fibrosis-related bacterial diseases, are increasingly difficult to treat and can be life-threatening. Over the last decades, an array of therapeutics and/or diagnostics have been exploited for management of pulmonary infections, but the advent of drug-resistant bacteria and the adverse conditions experienced upon reaching the lung environment urge the development of more effective delivery vehicles. Nanotechnology is revolutionizing the approach to circumventing these barriers, enabling better management of pulmonary infectious diseases. In particular, polymeric nanoparticle-based therapeutics have emerged as promising candidates, allowing for programmed design of multi-functional nanodevices and, subsequently, improved pharmacokinetics and therapeutic efficiency, as compared to conventional routes of delivery. Direct delivery to the lungs of such nanoparticles, loaded with appropriate antimicrobials and equipped with 'smart' features to overcome various mucosal and cellular barriers, is a promising approach to localize and concentrate therapeutics at the site of infection while minimizing systemic exposure to the therapeutic agents. The present review focuses on recent progress (2005-2015) important for the rational design of nanostructures, particularly polymeric nanoparticles, for the treatment of pulmonary infections with highlights on the influences of size, shape, composition, and surface characteristics of antimicrobial-bearing polymeric nanoparticles on their biodistribution, therapeutic efficacy, and toxicity. WIREs Nanomed Nanobiotechnol 2016, 8:842-871. doi: 10.1002/wnan.1401 For further resources related to this article, please visit the WIREs website.

Insights into host-pathogen interactions from state-of-the-art animal models of respiratory Pseudomonas aeruginosa infections

Pseudomonas aeruginosa is an important opportunistic pathogen that can cause acute respiratory infections in immunocompetent patients or chronic infections in immunocompromised individuals and in patients with cystic fibrosis. When acquiring the chronic infection state, bacteria are encapsulated within biofilm structures enabling them to withstand diverse environmental assaults, including immune reactions and antimicrobial therapy. Understanding the molecular interactions within the bacteria, as well as with the host or other bacteria, is essential for developing innovative treatment strategies. Such knowledge might be accumulated in vitro. However, it is ultimately necessary to confirm these findings in vivo. In the present Review, we describe state-of-the-art in vivo models that allow studying P. aeruginosa infections in molecular detail. The portrayed mammalian models exclusively focus on respiratory infections. The data obtained by alternative animal models which lack lung tissue, often provide molecular insights that are easily transferable to mammals. Importantly, these surrogate in vivo systems reveal complex molecular interactions of P. aeruginosa with the host. Herein, we also provide a critical assessment of the advantages and disadvantages of such models.

Inhalable Antimicrobials for Treatment of Bacterial Biofilm-Associated Sinusitis in Cystic Fibrosis Patients: Challenges and Drug Delivery Approaches

Bacterial biofilm-associated chronic sinusitis in cystic fibrosis (CF) patients caused by Pseudomonas aeruginosa infections and the lack of available treatments for such infections constitute a critical aspect of CF disease management. Currently, inhalation therapies to combat P. aeruginosa infections in CF patients are focused mainly on the delivery of antimicrobials to the lower respiratory tract, disregarding the sinuses. However, the sinuses constitute a reservoir for P. aeruginosa growth, leading to re-infection of the lungs, even after clearing an initial lung infection. Eradication of P. aeruginosa from the respiratory tract after a first infection has been shown to delay chronic pulmonary infection with the bacteria for up to two years. The challenges with providing a suitable treatment for bacterial sinusitis include: (i) identifying a suitable antimicrobial compound; (ii) selecting a suitable device to deliver the drug to the sinuses and nasal cavities; and (iii) applying a formulation design, which will mediate delivery of a high dose of the antimicrobial directly to the site of infection. This review highlights currently available inhalable antimicrobial formulations for treatment and management of biofilm infections caused by P. aeruginosa and discusses critical issues related to novel antimicrobial drug formulation design approaches.

Dry powder inhalable formulations for anti-tubercular therapy

Tuberculosis (TB) is an intracellular infectious disease caused by the airborne bacterium, Mycobacterium tuberculosis. Despite considerable research efforts, the treatment of TB continues to be a great challenge in part due to the requirement of prolonged therapy with multiple high-dose drugs and associated side effects. The delivery of pharmacological agents directly to the respiratory system, following the natural route of infection, represents a logical therapeutic approach for treatment or vaccination against TB. Pulmonary delivery is non-invasive, avoids first-pass metabolism in the liver and enables targeting of therapeutic agents to the infection site. Inhaled delivery also potentially reduces the dose requirement and the accompanying side effects. Dry powder is a stable formulation of drug that can be stored without refrigeration compared to liquids and suspensions. The dry powder inhalers are easy to use and suitable for high-dose formulations. This review focuses on the current innovations of inhalable dry powder formulations of drug and vaccine delivery for TB, including the powder production method, preclinical and clinical evaluations of inhaled dry powder over the last decade. Finally, the risks associated with pulmonary therapy are addressed. A novel dry powder formulation with high percentages of respirable particles coupled with a cost effective inhaler device is an appealing platform for TB drug delivery.

"The Good, the Bad and the Ugly" of Chitosans

The objective of this paper is to emphasize the fact that while consistent interest has been paid to the industrial use of chitosan, minor attention has been devoted to spread the knowledge of a good characterization of its physico-chemical properties. Therefore, the paper attempts to critically comment on the conflicting experimental results, highlighting the facts, the myths and the controversies. The goal is to indicate how to take advantage of chitosan versatility, to learn how to manage its variability and show how to properly tackle some unexpected undesirable features. In the sections of the paper various issues that relate chitosan properties to some basic features and to advanced solutions and applications are presented. The introduction outlines some historical pioneering works, where the chemistry of chitosan was originally explored. Thereafter, particular reference is made to analytical purity, characterization and chain modifications. The macromolecular characterization is mostly related to molecular weight and to degree of acetylation, but also refers to the conformational and rheological properties and solution stability. Then, the antimicrobial activity of chitosan in relation with its solubility is reviewed. A section is dedicated to the formulation of chitosan biomaterials, from gel to nanobeads, exploring their innovative application as active carrier nanoparticles. Finally, the toxicity issue of chitosan as a polymer and as a constructed nanomaterial is briefly commented in the conclusions.

Chronic lung infection by Pseudomonas aeruginosa biofilm is cured by L-Methionine in combination with antibiotic therapy

Bacterial biofilms are associated with 80-90% of infections. Within the biofilm, bacteria are refractile to antibiotics, requiring concentrations >1,000 times the minimum inhibitory concentration. Proteins, carbohydrates and DNA are the major components of biofilm matrix. Pseudomonas aeruginosa (PA) biofilms, which are majorly associated with chronic lung infection, contain extracellular DNA (eDNA) as a major component. Herein, we report for the first time that L-Methionine (L-Met) at 0.5 μM inhibits Pseudomonas aeruginosa (PA) biofilm formation and disassembles established PA biofilm by inducing DNase expression. Four DNase genes (sbcB, endA, eddB and recJ) were highly up-regulated upon L-Met treatment along with increased DNase activity in the culture supernatant. Since eDNA plays a major role in establishing and maintaining the PA biofilm, DNase activity is effective in disrupting the biofilm. Upon treatment with L-Met, the otherwise recalcitrant PA biofilm now shows susceptibility to ciprofloxacin. This was reflected in vivo, in the murine chronic PA lung infection model. Mice treated with L-Met responded better to antibiotic treatment, leading to enhanced survival as compared to mice treated with ciprofloxacin alone. These results clearly demonstrate that L-Met can be used along with antibiotic as an effective therapeutic against chronic PA biofilm infection.

Pseudomonas aeruginosa: arsenal of resistance mechanisms, decades of changing resistance profiles, and future antimicrobial therapies

Antimicrobial resistance is one of the most serious public health issues facing humans since the discovery of antimicrobial agents. The frequent, prolonged, and uncontrolled use of antimicrobial agents are major factors in the emergence of antimicrobial-resistant bacterial strains, including multidrug-resistant variants. Pseudomonas aeruginosa is a leading cause of nosocomial infections. The abundant data on the increased resistance to antipseudomonal agents support the need for global action. There is a paucity of new classes of antibiotics active against P. aeruginosa. Here, we discuss recent antibacterial resistance profiles and mechanisms of resistance by P. aeruginosa. We also review future potential methods for controlling antibiotic-resistant bacteria, such as phage therapy, nanotechnology and antipseudomonal vaccines.