Polymers as advanced antibacterial and antibiofilm agents for direct and combination therapies

Bioactive coating provides antimicrobial protection through immunomodulation and phage therapeutics

Medical implant-associated infections (IAI) is a growing threat to patients undergoing implantation surgery. IAI prevention typically relies on medical implants endowed with bactericidal properties achieved through surface modifications with antibiotics. However, the clinical efficacy of this traditional paradigm remains suboptimal, often necessitating revision surgery and posing potentially lethal consequences for patients. To bolster the existing anti-IAI arsenal, we propose herein a chitosan-based bioactive coating, i.e., ChitoAntibac, which exerts bacteria-inhibitory effects either through immune modulation or phage-directed microbial clearance, without relying on conventional antibiotics. The immuno-stimulating effects and phage-induced bactericidal properties can be tailored by engineering the loading dynamic of macrophage migration inhibitory factor (MIF), which polarizes macrophages towards the proinflammatory subtype (M1) with enhanced bacterial phagocytosis, and Staphylococcal Phage K, resulting in rapid and targeted pathogenic clearance (>99.99%) in less than 8 h. Our innovative antibacterial coating opens a new avenue in the pursuit of effective IAI prevention through immuno-stimulation and phage therapeutics.

Providing insight into the mechanism of action of cationic lipidated oligomers using metabolomics

The increasing resistance of clinically relevant microbes against current commercially available antimicrobials underpins the urgent need for alternative and novel treatment strategies. Cationic lipidated oligomers (CLOs) are innovative alternatives to antimicrobial peptides and have reported antimicrobial potential. An understanding of their antimicrobial mechanism of action is required to rationally design future treatment strategies for CLOs, either in monotherapy or synergistic combinations. In the present study, metabolomics was used to investigate the potential metabolic pathways involved in the mechanisms of antibacterial activity of one CLO, C12-o-(BG-D)-10, which we have previously shown to be effective against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. The metabolomes of MRSA ATCC 43300 at 1, 3, and 6 h following treatment with C12-o-(BG-D)-10 (48 µg/mL, i.e., 3× MIC) were compared to those of the untreated controls. Our findings reveal that the studied CLO, C12-o-(BG-D)-10, disorganized the bacterial membrane as the first step toward its antimicrobial effect, as evidenced by marked perturbations in the bacterial membrane lipids and peptidoglycan biosynthesis observed at early time points, i.e., 1 and 3 h. Central carbon metabolism and the biosynthesis of DNA, RNA, and arginine were also vigorously perturbed, mainly at early time points. Moreover, bacterial cells were under osmotic and oxidative stress across all time points, as evident by perturbations of trehalose biosynthesis and pentose phosphate shunt. Overall, this metabolomics study has, for the first time, revealed that the antimicrobial action of C12-o-(BG-D)-10 may potentially stem from the dysregulation of multiple metabolic pathways.IMPORTANCEAntimicrobial resistance poses a significant challenge to healthcare systems worldwide. Novel anti-infective therapeutics are urgently needed to combat drug-resistant microorganisms. Cationic lipidated oligomers (CLOs) show promise as new antibacterial agents against Gram-positive pathogens like methicillin-resistant Staphylococcus aureus (MRSA). Understanding their molecular mechanism(s) of antimicrobial action may help design synergistic CLO treatments along with monotherapy. Here, we describe the first metabolomics study to investigate the killing mechanism(s) of CLOs against MRSA. The results of our study indicate that the CLO, C12-o-(BG-D)-10, had a notable impact on the biosynthesis and organization of the bacterial cell envelope. C12-o-(BG-D)-10 also inhibits arginine, histidine, central carbon metabolism, and trehalose production, adding to its antibacterial characteristics. This work illuminates the unique mechanism of action of C12-o-(BG-D)-10 and opens an avenue to design innovative antibacterial oligomers/polymers for future clinical applications.

Lipase and pH-responsive diblock copolymers featuring fluorocarbon and carboxyl betaine for methicillin-resistant staphylococcus aureus infections

The emergence of multidrug-resistant bacteria along with their resilient biofilms necessitates the development of creative antimicrobial remedies. We designed versatile fluorinated polymer micelles with surface-charge-switchable properties, demonstrating enhanced efficacy against Methicillin-Resistant Staphylococcus Aureus (MRSA) in planktonic and biofilm states. Polymethacrylate diblock copolymers with pendant fluorocarbon chains and carboxyl betaine groups were prepared using reversible addition-fragmentation chain transfer polymerization. Amphiphilic fluorinated copolymers self-assembled into micelles, encapsulating ciprofloxacin in their cores (CIP@FCBMs) for antibacterial and antibiofilm applications. As a control, fluorine-free copolymer micelles loaded with ciprofloxacin (CIP@BCBMs) were prepared. Although both CIP@FCBMs and CIP@BCBMs exhibited pH-responsive surface charges and lipase-triggered drug release, CIP@FCBMs exhibited powerful antimicrobial and antibiofilm activities in vitro and in vivo, attributed to superior serum stability, higher drug loading, enhanced fluorination-facilitated cellular uptake, and lipase-triggered drug release. Collectively, reversing surface charge, on-demand antibiotic release, and fluorination-mediated nanoparticles hold promise for treating bacterial infections and biofilms.

Emerging polymeric materials for treatment of oral diseases: design strategy towards a unique oral environment

Oral diseases are prevalent but challenging diseases owing to the highly movable and wet, microbial and inflammatory environment. Polymeric materials are regarded as one of the most promising biomaterials due to their good compatibility, facile preparation, and flexible design to obtain multifunctionality. Therefore, a variety of strategies have been employed to develop materials with improved therapeutic efficacy by overcoming physicobiological barriers in oral diseases. In this review, we summarize the design strategies of polymeric biomaterials for the treatment of oral diseases. First, we present the unique oral environment including highly movable and wet, microbial and inflammatory environment, which hinders the effective treatment of oral diseases. Second, a series of strategies for designing polymeric materials towards such a unique oral environment are highlighted. For example, multifunctional polymeric materials are armed with wet-adhesive, antimicrobial, and anti-inflammatory functions through advanced chemistry and nanotechnology to effectively treat oral diseases. These are achieved by designing wet-adhesive polymers modified with hydroxy, amine, quinone, and aldehyde groups to provide strong wet-adhesion through hydrogen and covalent bonding, and electrostatic and hydrophobic interactions, by developing antimicrobial polymers including cationic polymers, antimicrobial peptides, and antibiotic-conjugated polymers, and by synthesizing anti-inflammatory polymers with phenolic hydroxy and cysteine groups that function as immunomodulators and electron donors to reactive oxygen species to reduce inflammation. Third, various delivery systems with strong wet-adhesion and enhanced mucosa and biofilm penetration capabilities, such as nanoparticles, hydrogels, patches, and microneedles, are constructed for delivery of antibiotics, immunomodulators, and antioxidants to achieve therapeutic efficacy. Finally, we provide insights into challenges and future development of polymeric materials for oral diseases with promise for clinical translation.

Bavachin Rejuvenates Sensitivity of Colistin against Colistin-Resistant Gram-Negative Bacteria

The emergence of plasmid-mediated colistin resistance threatens the efficacy of colistin as a last-resort antibiotic used to treat infection caused by Gram-negative bacteria (GNB). Given the shortage of new antibiotics, the discovery of adjuvants to existing antibiotics is a promising strategy to combat infections caused by multidrug-resistant (MDR) GNB. This study was designed to investigate the potential synergistic antibacterial activity of bavachin, a bioactive compound extracted from the Psoralea Fructus, combined with colistin against MDR GNB. Herein, the synergistic efficacy in vitro and the therapeutic efficacy of colistin combined with bavachin in vivo were evaluated. The synergistic mechanism was detected by fluorescent probe and the transcript levels of mcr-1. Bavachin combined with colistin showed an excellent synergistic activity against GNB, as the FICI ≤ 0.5. In contrast to colistin alone, combination therapy dramatically increased the survival rate of Galleria mellonella and mice in vivo. Moreover, the combination of bavachin and colistin significantly reduced the amount of bacterial biofilm formation, improved the membrane disruption of colistin and inhibited mcr-1 transcription. These findings show that bavachin is a potential adjuvant of colistin, which may provide a new strategy to combat colistin-resistant bacteria infection with lower doses of colistin.

Synthesis and antibacterial properties of fluorinated biodegradable cationic polyesters

Antimicrobial peptide-mimicking antibacterial polymers represent a practical strategy to conquer the ever-growing threat of antimicrobial resistance. Herein, we report the syntheses and antibacterial performance of degradable amphiphilic cationic polyesters containing pendent quaternary ammonium motifs and hydrophobic alkyl or fluoroalkyl groups. These polyesters were conveniently prepared from poly(3-methylene-1,5-dioxepan-2-one) via highly efficient one-pot successive thiol-Michael addition reactions. The antibacterial activity of these polyesters against S. aureus and E. coli and their hemolytic activity toward red blood cells were evaluated; some of them showed moderate antibacterial activity and selectivity against Gram-positive S. aureus. The membrane disruption mechanism of these cationic polyesters was briefly explored by monitoring the bacteria killing kinetics and SEM observations. Moreover, the effects of cationic/hydrophobic ratio and the incorporation of fluoroalkyl groups on the antibacterial activity and selectivity of the polyesters were demonstrated.

Adopting the "Missile boats-Aircraft carrier" strategy via human-contact friendly oxidized starch to achieve rapid-sustainably antibacterial paperboards

Polysaccharide-based antibacterial agents have received tremendous attention for the facile fabrication, low toxicity, and high compatibility with carbohydrate polymers. However, the antimicrobial mechanism, activity, and cytotoxicity for human-contact paperboards of oxidized starch (OST) with high carboxyl content, has not been explored. Herein, OST-27- 75 with 27- 75 wt% carboxyl contents were fabricated by H2O2 and coated on paperboards. Strikingly, OST-55 coating layer (16 g/m2) did not exfoliate from paperboard and possessed the rapid-sustainable antibacterial performance against Staphylococcus aureus and Escherichia coli. The soluble and insoluble components of OST-55 (OST55-S: OST55-IS mass ratio = 1: 2.1) presented different antimicrobial features and herein they were characterized by GC-MS, FT-IR, H-NMR, XRD, bacteriostatic activities, biofilm formation inhibition and intracellular constituent leakage to survey the antibacterial mechanism. The results revealed OST55-S displayed an amorphous structure and possessed superior antibacterial activity against S. aureus (MIC = 4 mg/mL) and E. coli (MIC = 8 mg/mL). Distinctively, OST55-S could rapidly ionize [H+] like "missile boats" from small molecule saccharides, while OST55-IS polyelectrolyte could continuously and slowly release for [H+] like an "aircraft carrier" to inhibit biofilm formation and disrupt cell structure. Eventually, the "Missile boats-Aircraft carrier" strategy provided a green methodology to fabricate polymeric antibacterial agents and expanded the use of cellulose-based materials.

Fabrication of chitosan/fibrin-armored multifunctional silver nanocomposites to improve antibacterial and wound healing activities

A wound healing substitute promotes rapid tissue regeneration and protects wound sites from microbial contamination. The silver-based antiseptic frequently moist skin stains, burns and irritation, penetrates deep wounds and protects against pathogenic infections. Thus, we formulated a novel fibrin/chitosan encapsulated silver nanoparticle (CH:F:SPG-CH:SNP) composites bandage accelerating the polymicrobial wound healing. Electrospinning method was employed to form the nano-porous, inexpensive, and biocompatible smart bandages. The structural, functional, and mechanical properties were analyzed for the prepared composites. The biological capacity of prepared CH:F:SPG-CH:SNP bandage was assessed against NIH-3 T3 fibroblast and HaCaT cell lines. In vitro hemolytic assays using red blood cells were extensively studied and explored the low hemolytic effect (4.5 %). In addition, the improved drug delivery nature captured for the CH:F:SPG-CH:SNP composite bandage. Antibacterial experiments were achieved against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Lactobacillus bulgaricus using zone inhibition method. Moreover, in-vivo wound healing efficacy of fabricated smart bandage was evaluated on the albino Wistar rats which revealed the significant improvement on the postoperative abdomen wounds.

A significant antibiofilm and antimicrobial activity of chitosan-polyacrylic acid nanoparticles against pathogenic bacteria

Chitosan is known to exert antimicrobial activity without the need for any chemical modification; however, new derivatives of chitosan can be created to target multi-drug resistant bacteria. In this study, chitosan (CS) was cross-linked with sodium tripolyphosphate to form nanoparticles, which were then coated with polyacrylic acid (PAA). The SEM images revealed that the CS-PAA nanoparticles had spherical shapes with smooth surfaces and the size of the dried nanoparticles was approximately 222 nm. Biofilm formation was significantly inhibited by 0.5 mg/mL of CS-PAA. In-situ optical microscopy showed that CS-PAA nanoparticles inhibited the bacterial biofilm formation in Campylobacter jejuni, Pseudomonas aeruginosa, and Escherichia coli after a single treatment with 40 μg. Additionally, 20 µg of CS-PAA nanoparticles demonstrated antibacterial activity against the growth of C. jejuni, P. aeruginosa, and E. coli with notable inhibitory zones of 9, 12, and 13 mm, respectively (P < 0.01). The development of a novel and ecofriendly method for the preparation of chitosan nanoparticles through an interaction of chitosan with PAA shows promise tool to combat bacterial infections and validates effective antibacterial and antibiofilm properties against antibiotic resistant pathogens.

Structure-activity relationship of drug conjugated polymeric materials against uropathogenic bacteria colonization under in vitro and in vivo settings

The human world has been plagued with different kinds of bacterial infections from time immemorial. The increased development of resistance towards commercial antibiotics has made these bacterial infections an even more critical challenge. Bacteria have modified their mode of interactions with different types of commercial drugs by bringing changes to the receptor proteins or by other resisting mechanisms like drug efflux. Various chemical approaches have been made to date to fight against these smart adapting species. Towards this, we hypothesize chemically modifying the commercial antibacterial drugs in order to deceive the bacteria and destroy the bacterial biomass. In this study, different molecular weight polyethyleneimines are taken and conjugated with some well-known commercial drugs like penicillin and chloramphenicol to explore their antibacterial properties against some of the laboratory and uro-pathogenic strains of Gram-positive and Gram-negative bacteria. A detailed structure-activity relationship of these polymeric prodrug-like materials has been evaluated to determine the optimum formulation. The standardized system not only shows significant ∼90% bacterial killing in liquid broth culture, but also demonstrates promising bacterial inhibition towards biofilm formation for the pathogenic strains on inanimate surfaces like urinary catheters and on an in vivo mouse skin abrasion model. The reported bioactive polymeric materials can be successfully used for widespread therapeutic applications with promising medical relevance.

Antibiotic adjuvants: synergistic tool to combat multi-drug resistant pathogens

The rise of multi-drug resistant (MDR) pathogens poses a significant challenge to the field of infectious disease treatment. To overcome this problem, novel strategies are being explored to enhance the effectiveness of antibiotics. Antibiotic adjuvants have emerged as a promising approach to combat MDR pathogens by acting synergistically with antibiotics. This review focuses on the role of antibiotic adjuvants as a synergistic tool in the fight against MDR pathogens. Adjuvants refer to compounds or agents that enhance the activity of antibiotics, either by potentiating their effects or by targeting the mechanisms of antibiotic resistance. The utilization of antibiotic adjuvants offers several advantages. Firstly, they can restore the effectiveness of existing antibiotics against resistant strains. Adjuvants can inhibit the mechanisms that confer resistance, making the pathogens susceptible to the action of antibiotics. Secondly, adjuvants can enhance the activity of antibiotics by improving their penetration into bacterial cells, increasing their stability, or inhibiting efflux pumps that expel antibiotics from bacterial cells. Various types of antibiotic adjuvants have been investigated, including efflux pump inhibitors, resistance-modifying agents, and compounds that disrupt bacterial biofilms. These adjuvants can act synergistically with antibiotics, resulting in increased antibacterial activity and overcoming resistance mechanisms. In conclusion, antibiotic adjuvants have the potential to revolutionize the treatment of MDR pathogens. By enhancing the efficacy of antibiotics, adjuvants offer a promising strategy to combat the growing threat of antibiotic resistance. Further research and development in this field are crucial to harness the full potential of antibiotic adjuvants and bring them closer to clinical application.

Ring-opening metathesis polymerization of N-methylpyridinium-fused norbornenes to access antibacterial main-chain cationic polymers

Cationic polymers have been identified as a promising type of antibacterial molecules, whose bioactivity can be tuned through structural modulation. Recent studies suggest that the placement of the cationic groups close to the core of the polymeric architecture rather than on appended side chains might improve both their bioactivity and selectivity for bacterial cells over mammalian cells. However, antibacterial main-chain cationic polymers are typically synthesized via polycondensations, which do not afford precise and uniform molecular design. Therefore, accessing main-chain cationic polymers with high degrees of molecular tunability hinges upon the development of controlled polymerizations tolerating cationic motifs (or cation progenitors) near the propagating species. Herein, we report the synthesis and ring-opening metathesis polymerization (ROMP) of N-methylpyridinium-fused norbornene monomers. The identification of reaction conditions leading to a well-controlled ROMP enabled structural diversification of the main-chain cationic polymers and a study of their bioactivity. This family of polyelectrolytes was found to be active against both Gram-negative (Escherichia coli) and Gram-positive (Methicillin-resistant Staphylococcus aureus) bacteria with minimal inhibitory concentrations as low as 25 µg/mL. Additionally, the molar mass of the polymers was found to impact their hemolytic activity with cationic polymers of smaller degrees of polymerization showing increased selectivity for bacteria over human red blood cells.

Antimicrobial polymer-siRNA polyplexes as a dual-mode platform for the treatment of wound biofilm infections

Treatment of wound biofilm infections faces challenges from both pathogens and uncontrolled host immune response. Treating both issues through a single vector would provide enhanced wound healing. Here, we report the use of a potent cationic antimicrobial polymer to generate siRNA polyplexes for dual-mode treatment of wound biofilms in vivo. These polyplexes act both as an antibiofilm agent and a delivery vehicle for siRNA for the knockdown of biofilm-associated pro-inflammatory MMP9 in host macrophages. The resulting polyplexes were effective in vitro, eradicating MRSA biofilms and efficiently delivering siRNA to macrophages in vitro with concomitant knockdown of MMP9. These polyplexes were likewise effective in an in vivo murine wound biofilm model, significantly reducing bacterial load in the wound (∼99% bacterial clearance) and reducing MMP9 expression by 80% (qRT-PCR). This combination therapeutic strategy dramatically reduced wound purulence and significantly expedited wound healing. Taken together, these polyplexes provide an effective and translatable strategy for managing biofilm-infected wounds.

Hierarchical assembly of foldable polymers and applications in organic optoelectronics and antibacterial or antiviral materials

Aggregation of amphiphilic polymers in block-selective solvents produces different nanostructures, which have been studied extensively for wide-ranging applications. Nevertheless, such immiscibility-driven aggregation does not endow them with the desired structural precision, predictability or surface functional group exposure, which significantly impact their functional applications. More recently, biomimetic folded structures of synthetic macromolecules (mostly oligomers) have come to the fore, but such studies have been limited to probe the secondary structures. In this article, we have collated hierarchical structures of foldamers, especially highlighting our recent contribution to the field of chain-folding regulated assembly of segmented polyurethanes (PUs) and their functional applications. A series of such PUs have been discussed, which contain a segmented hydrocarbon backbone and alternately placed pendant solvophilic groups. In either water or highly non-polar solvents (TCE, MCH), depending on the nature of the pendant group, they exhibit folded structures stabilized by intra-chain H-bonding. Hierarchical assembly of such folded chains by inter-chain H-bonding and/or π-stacking leads to the formation of well-defined nanostructures with functional applications ranging from organic optoelectronics to biomaterials. For example, a segmented PU with appended naphthalene-diimide (NDI) chromophores showed a pleated structure in MCH, which helped in organization of the NDI chromophores within π-stacking distance. Such folded polymer chains eventually produced nanotubular structures with excellent electron mobility. They also showed efficient intercalation of the pyrene (Py) donor by NDI-Py charge-transfer interaction and in this case the mixed nanotubular structure exhibited prominent room-temperature ferroelectricity. On the other hand, having cationic functionalities as the pendant groups such chain-folding regulated assembly produced unilamellar polymersomes with excellent antibacterial activity with very low minimum inhibitory concentrations (<10 μg mL-1). Replacing the pendant amine functionality with sulphate groups made these polyurethanes highly potent antiviral materials. In the absence of the alternating connectivity of the solvophobic and solvophilic segments or rigid hydrocarbon backbone, such folding propensity is destroyed, leading to structural collapse. While significant efforts have been made in correlating primary structures of wide-ranging polymers with their functional applications, this article demonstrates the direct correlation between the secondary structures of polymers and their functional properties.

A DNA Origami-based Bactericide for Efficient Healing of Infected Wounds

Bacteria infection is a significant obstacle in the clinical treatment of exposed wounds facing widespread pathogens. Herein, we report a DNA origami-based bactericide for efficient anti-infection therapy of infected wounds in vivo. In our design, abundant DNAzymes (G4/hemin) can be precisely organized on the DNA origami for controllable generation of reactive oxygen species (ROS) to break bacterial membranes. After the destruction of the membrane, broad-spectrum antibiotic levofloxacin (LEV, loaded in the DNA origami through interaction with DNA duplex) can be easily delivered into the bacteria for successful sterilization. With the incorporation of DNA aptamer targeting bacterial peptidoglycan, the DNA origami-based bactericide can achieve targeted and combined antibacterial therapy for efficiently promoting the healing of infected wounds. This tailored DNA origami-based nanoplatform provides a new strategy for the treatment of infectious diseases in vivo.

Antimicrobial-loaded biodegradable nanoemulsions for efficient clearance of intracellular pathogens in bacterial peritonitis

Intracellular pathogenic bacteria use immune cells as hosts for bacterial replication and reinfection, leading to challenging systemic infections including peritonitis. The spread of multidrug-resistant (MDR) bacteria and the added barrier presented by host cell internalization limit the efficacy of standard antibiotic therapies for treating intracellular infections. We present a non-antibiotic strategy to treat intracellular infections. Antimicrobial phytochemicals were stabilized and delivered by polymer-stabilized biodegradable nanoemulsions (BNEs). BNEs were fabricated using different phytochemicals, with eugenol-loaded BNEs (E-BNEs) affording the best combination of antimicrobial efficacy, macrophage accumulation, and biocompatibility. The positively-charged polymer groups of the E-BNEs bind to the cell surface of macrophages, facilitating the entry of eugenol that then kills the intracellular bacteria without harming the host cells. Confocal imaging and flow cytometry confirmed that this entry occurred mainly via cholesterol-dependent membrane fusion. As eugenol co-localized and interacted with intracellular bacteria, antibacterial efficacy was maintained. E-BNEs reversed the immunosuppressive effects of MRSA on macrophages. Notably, E-BNEs did not elicit resistance selection after multiple exposures of MRSA to sub-therapeutic doses. The E-BNEs were highly effective against a murine model of MRSA-induced peritonitis with better bacterial clearance (99 % bacteria reduction) compared to clinically-employed treatment with vancomycin. Overall, these findings demonstrate the potential of E-BNEs in treating peritonitis and other refractory intracellular infections.

Facial amphiphilic naphthoic acid-derived antimicrobial polymers against multi-drug resistant gram-negative bacteria and biofilms

Inspired by the facial amphiphilic nature and antimicrobial efficacy of many antimicrobial peptides, this work reported facial amphiphilic bicyclic naphthoic acid derivatives with different ratios of charges to rings that were installed onto side chains of poly(glycidyl methacrylate). Six quaternary ammonium-charged (QAC) polymers were prepared to investigate the structure-activity relationship. These QAC polymers displayed potent antibacterial activity against various multi-drug resistant (MDR) gram-negative pathogens such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Polymers demonstrated low hemolysis and high antimicrobial selectivity. Additionally, they were able to eradicate established biofilms and kill metabolically inactive dormant cells. The membrane permeabilization and depolarization results indicated a mechanism of action through membrane disruption. Two lead polymers showed no resistance from MDR-P. aeruginosa and MDR-K. pneumoniae. These facial amphiphiles are potentially a new class of potent antimicrobial agents to tackle the antimicrobial resistance for both planktonic and biofilm-related infections.

Antimicrobial polymer-loaded hydrogels for the topical treatment of multidrug-resistant wound biofilm infections

Integration of antimicrobial polymeric nanoparticles into hydrogel materials presents a promising strategy to address multidrug-resistant biofilm infections. Here we report an injectable hydrogel loaded with engineered cationic antimicrobial polymeric nanoparticles (PNPs) for the effective topical treatment of severe wound biofilm infections. The PNPs demonstrated biofilm penetration and disruption, resulting in the eradication of resistant and persister cells that reside within the biofilm. Significantly, PNPs did not elicit resistance development even after multiple exposures to sub-therapeutic doses. In vitro studies showed PNPs significantly reduced prolonged inflammation due to infection and promoted fibroblast migration. These PNPs were then incorporated into Poloxamer 407 (P407) hydrogels and utilized as an inert carrier for PNPs to provide a controlled and sustained topical release of the antimicrobial nanoparticles at the wound area. In vivo studies using a mature (4-day) wound biofilm infection in a murine model mimicking severe human wound infections demonstrated provided 99% bacterial biofilm clearance and significantly enhanced wound healing. Overall, this work demonstrated the efficacy and selectivity of the antimicrobial polymer-loaded hydrogel platform as a topical treatment for difficult-to-treat wound biofilm infections.

Self-Healing Antimicrobial Silicones-Mechanisms and Applications

Organosilicon polymers (silicones) are an important part of material chemistry and a well-established commercial product segment with a wide range of applications. Silicones are of enduring interest due to their unique properties and utility. Recently, new application areas for silicone-based materials have emerged, such as stretchable electronics, wearable stress sensors, smart coatings, and soft robotics. For this reason, research interest over the past decade has been directed towards new methods of crosslinking and increasing the mechanical strength of polyorganosiloxanes. The introduction of self-healing mechanisms may be a promising alternative for such high-value materials. This approach has gained both growing research interest and a rapidly expanding range of applications. Inherent extrinsic and intrinsic self-healing methods have been used in the self-healing of silicones and have resulted in significant advances in polymer composites and coatings, including multicomponent systems. In this review, we present a summary of research work dedicated to the synthesis and applications of self-healing hybrid materials containing polysiloxane segments, with a focus on antimicrobial and antifouling coatings.

Facially Amphiphilic Bile Acid-Functionalized Antimicrobials: Combating Pathogenic Bacteria, Fungi, and Their Biofilms

We report facially amphiphilic bile acid-based antimicrobials with a broad spectrum of activity against both bacterial and fungal pathogens and negligible detrimental effects on mammalian cells. Two lead compounds eliminated dormant subpopulations of various bacterial species, unlike conventional antibiotics. The lead compounds were also effective in eradicating biofilms of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Candida albicans. Additionally, these compounds substantially inhibited the formation of fungal biofilms (C. albicans). Mechanistic investigations revealed the membrane-active nature and endogenous reactive oxygen species (ROS) induction ability of these compounds. Finally, no detectable resistance was developed by the bacterial strains against this class of membrane-targeting antimicrobials.

Advances in Material Modification with Smart Functional Polymers for Combating Biofilms in Biomedical Applications

Biofilms as living microorganism communities are found anywhere, and for the healthcare sector, these constitute a threat and allied mechanism for health-associated or nosocomial infections. This review states the basis of biofilms and their formation. It focuses on their relevance for the biomedical sector, generalities, and the major advances in modified or new synthesized materials to prevent or control biofilm formation in biomedicine. Biofilm is conceptualized as an aggregate of cells highly communicated in an extracellular matrix, which the formation obeys to molecular and genetic basis. The biofilm offers protection to microorganisms from unfavorable environmental conditions. The most frequent genera of microorganisms forming biofilms and reported in infections are Staphylococcus spp., Escherichia spp., and Candida spp. in implants, heart valves, catheters, medical devices, and prostheses. During the last decade, biofilms have been most commonly related to health-associated infections and deaths in Europe, the United States, and Mexico. Smart, functional polymers are materials capable of responding to diverse stimuli. These represent a strategy to fight against biofilms through the modification or synthesis of new materials. Polypropylene and poly-N-isopropyl acrylamide were used enough in the literature analysis performed. Even smart polymers serve as delivery systems for other substances, such as antibiotics, for biofilm control.

pH Window for High Selectivity of Ionizable Antimicrobial Polymers toward Bacteria

Antimicrobial polymers exhibit great potential for treating drug-resistant bacteria; however, designing antimicrobial polymers that can selectively kill bacteria and cause relatively low toxicity to normal tissues/cells remains a key challenge. Here, we report a pH window for ionizable polymers that exhibit high selectivity toward bacteria. Ionizable polymer PC6A showed the greatest selectivity (131.6) at pH 7.4, exhibiting low hemolytic activity and high antimicrobial activity against bacteria, whereas a very high or low protonation degree (PD) produced relatively low selectivity (≤35.6). Bactericidal mechanism of PC6A primarily comprised membrane lysis without inducing drug resistance even after consecutive incubation for 32 passages. Furthermore, PC6A demonstrated synergistic effects in combination with antibiotics at pH 7.4. Hence, this study provides a strategy for designing selective antimicrobial polymers.

Amphiphilic Nano-Swords for Direct Penetration and Eradication of Pathogenic Bacterial Biofilms

Bacterial biofilms are major causes of persistent and recurrent infections and implant failures. Biofilms are formable by most clinically important pathogens worldwide, such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, causing recalcitrance to standard antibiotic therapy or anti-biofilm strategies due to amphiphilic impermeable extracellular polymeric substances (EPS) and the presence of resistant and persistent bacteria within the biofilm matrix. Herein, we report our design of an oligoamidine-based amphiphilic "nano-sword" with high structural compacity and rigidity. Its rigid, amphiphilic structure ensures effective penetration into EPS, and the membrane-DNA dual-targeting mechanism exerts strong bactericidal effect on the dormant bacterial persisters within biofilms. The potency of this oligoamidine is shown in two distinct modes of application: it may be used as a coating agent for polycaprolactone to fully inhibit surface biofilm growth in an implant-site mimicking micro-environment; meanwhile, it cures model mice of biofilm infections in various ex vivo and in vivo studies.

Design of Quorum Sensing Inhibitor-Polymer Conjugates to Penetrate Pseudomonas aeruginosa Biofilms

Antimicrobial resistance (AMR) is a global threat to public health with a forecast of a negative financial impact of one trillion dollars per annum, hence novel therapeutics are urgently needed. The resistance of many bacteria against current drugs is further augmented by the ability of these microbes to form biofilms where cells are encased in a slimy extracellular matrix and either adhered to a surface or forming cell aggregates. Biofilms form physiochemical barriers against the penetration of treatments such as small molecule antibacterials, rendering most treatments ineffective. Pseudomonas aeruginosa, a priority pathogen of immediate concern, controls biofilm formation through multiple layers of gene regulation pathways including quorum sensing (QS), a cell-to-cell signaling system. We have recently reported a series of inhibitors of the PqsR QS regulator from this organism that can potentiate the action of antibiotics. However, these QS inhibitors (QSIs) have shown modest effects on biofilms in contrast with planktonic cultures due to poor penetration through the biofilm matrix. To enhance the delivery of the inhibitors, a small library of polymers was designed as carriers of a specific QSI, with variations in the side chains to introduce either positively charged or neutral moieties to aid penetration into and through the P. aeruginosa biofilm. The synthesized polymers were evaluated in a series of assays to establish their effects on the inhibition of the Pqs QS system in P. aeruginosa, the levels of inhibitor release from polymers, and their impact on biofilm formation. A selected cationic polymer-QSI conjugate was found to penetrate effectively through biofilm layers and to release the QSI. When used in combination with ciprofloxacin, it enhanced the biofilm antimicrobial activity of this antibiotic compared to free QSI and ciprofloxacin under the same conditions.

Piezoelectric Nanozyme for Dual-Driven Catalytic Eradication of Bacterial Biofilms

Catalytic nanomedicine can in situ catalytically generate bactericidal species under external stimuli to defend against bacterial infections. However, bacterial biofilms seriously impede the catalytic efficacy of traditional nanocatalysts. In this work, MoSe2 nanoflowers (NFs) as piezoelectric nanozymes were constructed for dual-driven catalytic eradication of multi-drug-resistant bacterial biofilms. In the biofilm microenvironment, the piezoelectricity of MoSe2 NFs was cascaded with their enzyme-mimic activity, including glutathione oxidase-mimic and peroxidase-mimic activity. As a result, the oxidative stress in the biofilms was sharply elevated under ultrasound irradiation, achieving a 4.0 log10 reduction of bacterial cells. The in vivo studies reveal that the MoSe2 NFs efficiently relieve the methicillin-resistant Staphylococcus aureus bacterial burden in mice under the control of ultrasound at a low power density. Moreover, because of the surface coating of antioxidant poly(ethyleneimine), the dual-driven catalysis of MoSe2 NFs was retarded in normal tissues to minimize the off-target damage and favor the wound healing process. Therefore, the cascade of piezoelectricity and enzyme-mimic activity in MoSe2 NFs reveals a dual-driven strategy for improving the performance of catalytic nanomaterials in the eradication of bacterial biofilms.

Designer co-beta-peptide copolymer selectively targets resistant and biofilm Gram-negative bacteria

New antimicrobials are urgently needed to combat Gram-negative bacteria, particularly multi-drug resistant (MDR) and phenotypically resistant biofilm species. At present, only sequence-defined alpha-peptides (e.g. polymyxin B) can selectively target Gram-negative bacterial lipopolysaccharides. We show that a copolymer, without a defined sequence, shows good potency against MDR Gram-negative bacteria including its biofilm form. The tapered blocky co-beta-peptide with controlled N-terminal hydrophobicity (#4) has strong interaction with the Gram-negative bacterial lipopolysaccharides via its backbone through electrostatic and hydrogen bonding interactions but not the Gram-positive bacterial and mammalian cell membranes so that this copolymer is non-toxic to these two latter cell types. The new #4 co-beta-peptide selectively kills Gram-negative bacteria with low cytotoxicity both in vitro and in a mouse biofilm wound infection model. This strategy provides a new concept for the design of Gram-negative selective antimicrobial peptidomimetics against MDR and biofilm species.

Chemical Basis of Combination Therapy to Combat Antibiotic Resistance

The antimicrobial resistance crisis is a global health issue requiring discovery and development of novel therapeutics. However, conventional screening of natural products or synthetic chemical libraries is uncertain. Combination therapy using approved antibiotics with inhibitors targeting innate resistance mechanisms provides an alternative strategy to develop potent therapeutics. This review discusses the chemical structures of effective β-lactamase inhibitors, outer membrane permeabilizers, and efflux pump inhibitors that act as adjuvant molecules of classical antibiotics. Rational design of the chemical structures of adjuvants will provide methods to impart or restore efficacy to classical antibiotics for inherently antibiotic-resistant bacteria. As many bacteria have multiple resistance pathways, adjuvant molecules simultaneously targeting multiple pathways are promising approaches to combat multidrug-resistant bacterial infections.

Glycopolymers against pathogen infection

Pathogens including viruses, bacteria, fungi, and parasites continue to shape our lives in profound ways every day. As we have learned to live in parallel with pathogens, we have gained a better understanding of the rules of engagement for how they bind, adhere, and invade host cells. One such mechanism involves the exploitation of host cell surface glycans for attachment/adhesion, one of the first steps of infection. This knowledge has led to the development of glycan-based diagnostics and therapeutics for the treatment and prevention of infection. One class of compounds that has become increasingly important are the glycopolymers. Glycopolymers are macromolecules composed of a synthetic scaffold presenting carbohydrates as side chain motifs. Glycopolymers are particularly attractive because their properties can be tuned by careful choice of the scaffold, carbohydrate/glycan, and overall presentation. In this review, we highlight studies over the past ten years that have examined the role of glycopolymers in pathogen adhesion and host cell infection, biofilm formation and removal, and drug delivery with the aim of examining the direct effects of these macromolecules on pathogen engagement. In addition, we also examine the role of glycopolymers as diagnostics for the detection and monitoring of pathogens.

Theranostic FRET Gate to Visualize and Quantify Bacterial Membrane Breaching

Designing new antimicrobial-cum-probes to study real-time bacterial membrane breaching and concurrently developing inquisitorial image-based analytical tools is essential for the treatment of infectious diseases. An array of aggregation-induced emission (AIE) polymers (donor) consisting of neutral, anionic, and cationic charges were designed and employed as antimicrobial theranostic gatekeepers for the permeabilization of the peptidoglycan layer-adherable crystal violet (CV, acceptor). An AIE-active tetraphenylethylene (TPE)-tagged polycaprolactone biodegradable platform was chosen, and their self-assembled tiny amphiphilic nanoparticles were employed as a gatekeeper in the construction of bacterial membrane-reinforced fluorescent resonance energy transfer (FRET) probes. Electrostatic adhering of the cationic AIE polymer and subsequent gate opening aided fluorescent FRET probe activation on the membrane of Gram-negative bacteria, Escherichia coli. The selective photoexcitation energy transfer process in confocal microscopy experiments facilitated the building of a visualization-based FRET assay for the quantification of bactericidal activity. Nonantimicrobial AIE polymers (neutral and anionic) did not breach the bacterial membrane, resulting in no FRET signal. Detailed photophysical studies were done to establish the FRET probe mechanism, and a proof of concept was established.

Peptidoglycan-Directed Chemical Ligation for Selective Inhibition on Gram-Positive Bacteria

Microbicides with distinct antibacterial mechanisms show potential to combat multi-drug resistance bacteria. We herein report peptidoglycan-directed chemical ligation (PGCL) between alkyne-bearing vancomycin and an azide-tagged cationic polymer. The former binds peptidoglycan and inhibits peptidoglycan crosslinking, while the latter interferes the integrity of the bacterial membrane. PGCL results in enhanced bactericidal activity against Gram-positive Staphylococcus aureus (S. aureus) over Gram-negative Escherichia coli (E. coli). These data indicate the potential of PGCL to selectively and synergistically inhibit Gram-positive pathogens via dual modality antibacterial mechanisms of peptidoglycan-inhibiting antibiotics and bacterial membrane-disrupting polycations.

Elucidating the role of multivalency, shape, size and functional group density on antibacterial activity of diversified supramolecular nanostructures enabled by templated assembly

With the increased prevalence of antibiotic-resistant infections, there is an urgent need to develop novel antibacterial materials. In addition, gaining a complete understanding of the structural features that impart activity toward target microorganisms is essential to enable materials optimisation. Here we have reported a rational design to fabricate antibacterial supramolecular nanoparticles with variable shape, size and cationic group density, by exploiting noncovalent interactions between a shape determining template amphiphile and a cationic amphiphile to introduce charge on the nanoparticle surface. We have shown that the monomeric cationic amphiphile alone showed poor antibacterial activity, whereas nanostructures formed by co-assembling the complementary units showed significantly enhanced antibacterial efficiency. Further, the systematic variation of several structural parameters such as shape, spacing between the cationic groups and size of these nanostructures allowed us to elicit the role of each parameter on the overall antibacterial properties. Finally, we investigated the origin of the differing antibacterial activity of these nanoparticles having different shape and size but with the same molecular composition, by comparing the thermodynamic parameters of their binding interactions with a bacterial membrane mimic.

Synthesis of sustainable eugenol/hydroxyethylmethacrylate-based polymers with antioxidant and antimicrobial properties

Eugenol is a phenolic monoterpenoid, emplyed in this study to obtain bio-based antimicrobial and antioxidant methacrylate polymers.

Enzyme-triggered smart antimicrobial drug release systems against bacterial infections

The rapid emergence and spread of drug-resistant bacteria, as one of the most pressing public health threats, are declining our arsenal of available antimicrobial drugs. Advanced antimicrobial drug delivery systems that can achieve precise and controlled release of antimicrobial agents in the microenvironment of bacterial infections will retard the development of antimicrobial resistance. A variety of extracellular enzymes are secreted by bacteria to destroy physical integrity of tissue during their invasion of host body, which can be utilized as stimuli to trigger "on-demand" release of antimicrobials. In the past decade, such bacterial enzyme responsive drug release systems have been intensively studied but few review has been released. Herein, we systematically summarize the recent progress of smart antimicrobial drug delivery systems triggered by bacteria secreted enzymes such as lipase, hyaluronidase, protease and antibiotic degrading enzymes. The perspectives and existing key issues of this field will also be discussed to fuel the innovative research and translational application in the future.

Tackling Antibiotic Resistance: Influence of Aliphatic Branches on Broad-Spectrum Antibacterial Polytriazoles against ESKAPE Group Pathogens

One of the most important threats to public health is the appearance of multidrug-resistant pathogenic bacteria, since they are the cause of a high number of deaths worldwide. Consequently, the preparation of new effective antibacterial agents that do not generate antimicrobial resistance is urgently required. We report on the synthesis of new linear cationic antibacterial polytriazoles that could be a potential source of new antibacterial compounds. These polymers were prepared by thermal- or copper-catalyzed click reactions of azide and alkyne functions. The antibacterial activity of these materials can be modulated by varying the size or nature of their side chains, as this alters the hydrophilic/hydrophobic balance. Antibacterial activity was tested against pathogens of the ESKAPE group. The P3TD polymer, which has butylated side chains, was found to have the highest bactericidal activity. The toxicity of selected polytriazoles was investigated using human red blood cells and a human gingival fibroblast cell line. The propensity of prepared polytriazoles to induce resistance in certain bacteria was studied. Some of them were found to not produce resistance in methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa. The interaction of these polytriazoles with the Escherichia coli membrane produces both depolarization and disruption of the membrane.

Recent Advances in the Development of Lipid-, Metal-, Carbon-, and Polymer-Based Nanomaterials for Antibacterial Applications

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Two plus One: Combination Therapy Tri-systems Involving Two Membrane-Disrupting Antimicrobial Macromolecules and Antibiotics

The escalating issue of multidrug-resistant (MDR) bacteria indicates the urgent need for new and effective strategies to combat this global health challenge. Here, we describe a new combinatorial approach that can be put forward for experimental therapy application against MDR bacteria. Specifically, we have developed a tri-system that includes the coadministration of two different membrane-disrupting-type antimicrobial agents─a synthetic antimicrobial polymer P and an antimicrobial peptide (AMP) colistin methanesulfonate (Col)─in conjunction with an antibiotic [doxycycline (Dox), rifampicin (Rif), or azithromycin (Azi)]. Traditionally, the administration of membrane-disrupting antimicrobial agents causes toxicity, but, in comparison, we demonstrated synergy and biocompatibility using this combinatorial approach. Checkerboard assays showed the occurrence of synergistic interactions in Col-Dox-P, Col-Rif-P, and Col-Azi-P tri-systems against wild-type and MDR Pseudomonas aeruginosa, with the Col-Dox-P system being the most effective. The ability to synergize thus enables the use of a lower dosage in combinations compared to the standalone agents. The tri-systems not only demonstrated bacteriostatic activity but were also bactericidal. For example, the Col-Dox-P system (at 8, 4, and 8 μg mL^-1, respectively) and the Col-Rif-P system (at 4, 8, and 16 μg mL^-1, respectively) were able to kill >99.999% of planktonic P. aeruginosa cells within 3 h of treatment. More importantly, an improvement of the therapeutic/selectivity index was achieved via combination therapy. Taking the Col-Dox-P system as an example, its biocompatibility with murine embryonic fibroblast cells was found to be comparable to that of polymer P alone despite the synergistic enhancement in antimicrobial activity of the combination. This resulted in a significant increase in selectivity by 16-fold for the Col-Dox-P combination system compared to P alone. Furthermore, the broad applicability of this tri-system strategy was demonstrated via the successful application of the AMP melittin in place of Col or P. Overall, this study sheds new insights on the application of membrane-disrupting antimicrobial agents in combination therapy and their potential for safer clinical use. Additionally, the information gathered in this study could inform the development of future combination therapy systems involving the simultaneous employment of multiple AMPs with antibiotics.

Characterization, Properties and Antimicrobial Activity of Radiation Induced Phosphorus-Containing PVA Hydrogels

Function modification of polyvinyl alcohol (PVA) having phosphorus-containing heterocyclic compounds is believed to have thermal and biological applications in the area of polymers. The synthesis of phosphorus-containing PVA (P-PVA) was performed using γ-radiation. The chemical structure of the composite polymer is confirmed by spectroscopic techniques of FT-IR, 1H, 13C, and 31P-NMR. Photosensitive properties of polymers were investigated by ultraviolet spectroscopy. Thermal studies are assigned using the Differential Scanning Calorimeter (DSC) and thermogravimetric analysis (TGA). Data display that P-PVA has more thermal stability than PVA. The surface morphology of the prepared hydrogels was performed using scanning electron microscopy (SEM). Quantitative elemental analysis of the P-PVA hydrogel was done through energy-dispersive X-ray spectroscopy (EDX). Antimicrobial activity of the prepared hydrogels using different fungi such as Aspergillus fumigatus, Geotrichum candidum, Candida albicans, and Syncephal-astrum racemosum, in addition to bacteria such as Staphylococcus aureus, Bacillis subtilis (as gram-positive bacteria), Pseudomonas aeruginosa, and Escherichia coli (as gram-negative bacteria), was studied. The phosphorus-contained PVA hydrogels were found to have antimicrobial activity against various fungi and bacteria compared to pure PVA hydrogels.

Facile Preparation of Polysaccharide-Polypeptide Conjugates via a Biphasic Solution Ring-Opening Polymerization

Polysaccharide-polypeptide conjugates have gained a broad interest in mimicking the structure and bioactivity of peptidoglycans or proteoglycans for biomedical applications. Efficient and precise preparation of the conjugates is challenging and unresolved, mainly because of the mismatched solubility between polysaccharide initiators and N-carboxyanhydrides (NCAs), which frequently results in competing side reactions and oligomeric polypeptide chain. Herein, we report a facile and efficient strategy to prepare the conjugates with well-controlled polypeptide chain length (l_p) directly from unmodified polysaccharides via a biphasic solution ring-opening polymerization. The effect of l_p on surface antibacterial properties has been investigated. Elongating the l_p can significantly potentiate the antibiofilm property of the conjugate coatings. Our results may provide opportunities to develop various polypeptide-based conjugates with well-defined structures toward versatile uses.

Self-Healing Thiolated Pillar[5]arene Films Containing Moxifloxacin Suppress the Development of Bacterial Biofilms

Polymer self-healing films containing fragments of pillar[5]arene were obtained for the first time using thiol/disulfide redox cross-linking. These films were characterized by thermogravimetric analysis and differential scanning calorimetry, FTIR spectroscopy, and electron microscopy. The films demonstrated the ability to self-heal through the action of atmospheric oxygen. Using UV–vis, 2D 1H-1H NOESY, and DOSY NMR spectroscopy, the pillar[5]arene was shown to form complexes with the antimicrobial drug moxifloxacin in a 2:1 composition (logK11 = 2.14 and logK12 = 6.20). Films containing moxifloxacin effectively reduced Staphylococcus aureus and Klebsiella pneumoniae biofilms formation on adhesive surfaces.

Cationic porphyrin-based nanoparticles for photodynamic inactivation and identification of bacteria strains

The emergence of antibiotic drug resistance has undermined the efficacy of antibiotics, and is becoming a severe threat to public health. To combat antibiotic drug resistance and to replace traditional antibiotic treatment, an alternative strategy based on antibacterial photodynamic therapy (APDT), which has broad applicability, high efficiency and less potential of developing antibiotic drug resistance, has been developed. In this work, the cationic porphyrin-based nanoparticles (NPs) were prepared by epoxy-amine chain extension polymerization of diepoxy-terminated poly(ethylene glycol) (PEG) and tetraamino-containing porphyrin, followed by quaternization with methyl iodine and butyl bromide. The as-obtained cationic porphyrin NPs preserved the photophysical properties of porphyrin derivatives, and can efficiently generate singlet oxygen (¹O₂) under 635 nm laser irradiation. The cationic porphyrin-based NPs displayed intrinsic antibacterial properties, and exhibited strong APDT effect on Gram-positive bacteria by destroying the bacterial cell membranes. Upon incubation with different bacterial strains, it was found that they could be utilized to identify Gram-positive bacteria by observing the sedimentation behavior of their mixtures, and visualizing their co-cultured and centrifugal bacteria cakes. In addition, the cationic porphyrin-based NPs had good hemocompatibility and low dark cytotoxicity.

Atomic-Resolution Structures and Mode of Action of Clinically Relevant Antimicrobial Peptides

Global rise of infections and deaths caused by drug-resistant bacterial pathogens are among the unmet medical needs. In an age of drying pipeline of novel antibiotics to treat bacterial infections, antimicrobial peptides (AMPs) are proven to be valid therapeutics modalities. Direct in vivo applications of many AMPs could be challenging; however, works are demonstrating encouraging results for some of them. In this review article, we discussed 3-D structures of potent AMPs e.g., polymyxin, thanatin, MSI, protegrin, OMPTA in complex with bacterial targets and their mode of actions. Studies on human peptide LL37 and de novo-designed peptides are also discussed. We have focused on AMPs which are effective against drug-resistant Gram-negative bacteria. Since treatment options for the infections caused by super bugs of Gram-negative bacteria are now extremely limited. We also summarize some of the pertinent challenges in the field of clinical trials of AMPs.