Addressing MRSA infection and antibacterial resistance with peptoid polymers

Isoniazid potentiates tigecycline to kill methicillin-resistant Staphylococcus aureus

Therapeutic option for treating methicillin-resistant Staphylococcus aureus (MRSA) infection is urgently required since its resistance to a broad spectrum of currently available antibiotics. Here, we report that isoniazid is able to potentiate the killing efficacy of tigecycline to MRSA. The combination of isoniazid and tigecycline reduces the minimal inhibitory concentration of clinic MRSA strains to tigecycline. The killing activity of tigecycline is further confirmed by killing experiments and murine infection model. We further demonstrate the mechanism that isoniazid increases intracellular accumulation of tigecycline by promoting the influx but limiting the efflux of tigecycline through proton motive force. We also show that isoniazid and tigecycline synergize to increase the abundance of isoniazid-NAD adduct, which in turn damage cell membrane, possibly contributing to the disruption of PMF. Whereas phosphatidylethanolamine and cardiolipin are able to abrogate the synergistic effect of isoniazid plus tigecycline. Thus our study provides a new perspective that antibiotics, e.g. isoniazid, once recognized only to target Mycobacterium tuberculosis, can be repurposed as antibiotic adjuvant to tigecycline, expanding our choice of antibiotic-antibiotic combinations in treating bacterial infectious diseases.

Unraveling persistent bacteria: Formation, niches, and eradication strategies

Persistent bacteria (persisters) are phenotypic variants that emerge either randomly or in response to a range of adverse environmental conditions. Persistence represents a state whereby a subpopulation of microorganisms can spontaneously enter a "dormant" state in response to environmental factors, while simultaneously exhibiting elevated tolerance to antimicrobial agents. This review provides the current definition of bacterial persistence and summarizes the mechanisms of persisters formation as well as the various niches of bacterial persistence encountered in clinical practice. Strategies targeting persisters are outlined, including but not limited to direct killing, awakening of persistent bacteria, combined clearance, and inhibition of persistence formation, and we conclude by proposing challenges and solutions for addressing bacterial persistence in current clinical practice.

Synthesis and antimicrobial evaluation of novel quaternary quinolone derivatives with low toxicity and anti-biofilm activity

To overcome the increasing global drug resistance, the development of novel antimicrobial drugs is a top priority in the fight against multidrug resistant (MDR) and persistent bacteria. In this work, we report the synthesis of novel single quaternary quinolone antibacterial agents. The majority of the tested compounds exhibited significant antimicrobial efficacy against Gram-negative pathogens (E. coli and S. maltophilia). Notably, the selected compound (4e) was highly inhibitory with a MIC value of 0.25 μg/mL against E. coli. Additionally, compound 4e demonstrated excellent stability in complex biological fluids with low hemolytic activity (HC50 > 1280 μg/mL) and a significantly lower propensity to induce bacterial resistance. Encouragingly, 4e showed not only rapid bactericidal activity and inhibition of bacterial biofilms, but also low toxicity to erythrocytes and RAW 264.7 cells compared to the clinical drug ciprofloxacin. Mechanism studies have found that compound 4e has a relatively weak destructive effect on the cell membrane of E. coli. However, it can effectively inhibit the activity of glutathione (GSH), promote the massive accumulation of intracellular reactive oxygen species (ROS), and then disrupt the antioxidant defense system of bacteria, achieving a bactericidal effect. In addition, compound 4e has a certain binding effect with bacterial DNA.

Ultrasmall coinage metal nanoclusters as promising antibacterial agents: from design to applications

Ultrasmall coinage metal nanoclusters (MNCs, <3 nm) have emerged as a novel class of broad-spectrum antibacterials due to their unique physicochemical properties. The rapid advances in the design and applications of MNC-based antibacterials are made possible by the atomic-level core-shell engineering of MNCs. In this review, we initially explore the fundamental requirements for MNC-based antibacterials. Following this, we emphasize the significance of antibacterial modalities in the design and application of these agents by summarizing the key antibacterial modalities of MNCs and highlighting their mechanisms of action. We then outline the primary design strategies for MNC-based antibacterials. In the subsequent section, we provide an overview of the representative antibacterial applications of MNC-based antibacterials across various scenarios. Finally, we offer a comprehensive summary along with the current opportunities and challenges faced by MNC-based antibacterials. We believe that this review will illuminate the design of MNC-based antibacterials for future applications and inspire further innovative research in their development.

Chemical Innovations of Antimicrobial Polymers for Combating Antimicrobial Resistance

The global rise of antimicrobial resistance (AMR) has rendered many traditional antibiotics ineffective, leading to an urgent need for alternative therapeutic strategies. Antimicrobial polymers, with their ability to rapidly kill bacteria by disrupting or crossing membranes and/or targeting multiple microbial functions without inducing resistance, offer a promising solution. This perspective explores recent innovations in the design and synthesis of antimicrobial polymers, focusing on their chemical motifs, structural derivatives, and their applications in combating systemic and topical infections. We also highlight key challenges in translating these materials from laboratory research to clinical practice, including issues related to the high dose required, bioavailability and stability in systemic infection treatment, and ability to disperse and kill biofilms in localized infection management. By addressing these challenges, antimicrobial polymers could play a crucial role in the development of next-generation therapeutics to combat multidrug-resistant pathogens. This perspective attempts to summarize significant insights for the design and development of advanced antimicrobial polymers to overcome AMR, offering potential pathways to improve clinical outcomes in treating systemic and local infections.

Exploration of membrane-active cephalosporin derivatives as potent antibacterial agents against Staphylococcus aureus biofilms and persisters

Developing innovative antimicrobial agents is essential in the fight against drug-resistant bacteria, as well as biofilms and persistent bacteria. In this study, four series of amphiphilic cephalosporin derivatives were synthesized. Most of the compounds showed good activity against Gram-positive bacteria, among which membrane-active cephalosporin 15e showed high activity against Staphylococcus aureus. Furthermore, 15e can maintain antimicrobial activity in mammalian body fluids and does not develop detectable resistance. Antibacterial mechanism studies demonstrated that the compound 15e can destroy the bacterial cell membrane, causing leakage of intracellular nucleic acids and proteins. Moreover, it can also suppress bacterial metabolic activity and induce the accumulation of reactive oxygen species (ROS) in the bacteria. Of greater significance, compound 15e effectively prevented the formation of biofilms and eradicated established biofilms and persister cells. Notably, compound 15e exhibited potent in vivo antibacterial efficacy, which was better than cephalothin. These findings suggest that 15e has a potential to become a drug candidate for treating bacterial infections.

High Antibacterial Activity and Selectivity of Cationic Disubstituted Polypeptoids with Stable Helices and Enzymatic Resistance

High antibacterial activity, low mammalian cell toxicity, and serum stability are crucial parameters for designing efficient antibacterial materials under physiological conditions. This relies on a deep understanding of the structure-property relationship of antibacterial materials. In this study, a series of cationic amphiphilic disubstituted polypeptoids were synthesized by using ring-opening polymerization (ROP) followed by thiol-ene click reactions. This new class of peptidomimetic materials, with chiral centers at backbones and ammonium alkyl N-substituents, exhibited remarkably stable helical structures independent of pH, temperature, salt, and denaturing agents. The helical analogs were found to show higher antibacterial activity against both Gram-negative and Gram-positive strains than the racemic, nonhelical counterparts. The helical structure and the balance of cationic charges and hydrophobicity were key parameters to achieve high selectivity for bacteria over mammalian cells. Moreover, unlike poly(l-lysine), the disubstituted polypeptoids, with stable helices and enzymatic resistance, retained high antibacterial activity even in the presence of salts, human serum albumin (HSA), and protease trypsin at physiological concentrations. This study deepens our understanding of how structural elements correlate with antibacterial activity and selectivity. In addition, the helical and enzymatically stable disubstituted polypeptoids have shown promise as an attractive platform for the design of new antibacterial materials with high efficiency and low toxicity.

Bacterial Specific Recognition of Sulfonium Poly(Amino Acid) Adsorbents for Ultrafast MRSA Capture Against Bloodstream Infection

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections pose significant health risks, potentially leading to severe conditions such as bacteremia. Developing effective treatments to eliminate resistant bacteria from the bloodstream, simultaneously mitigate infection-related complications, and reduce mortality remains challenging. Herein, microspheres are synthesized with bacterial elimination and inflammation prevention by crosslinked sulfonium poly(amino acids). As-synthesized microsphere, PM1 0.6B MS, exhibits an ultrafast adsorption efficiency of 0.41 × 108 CFU mg-1 min-1 for MRSA, which positions the highest index among the reported resin and inorganic adsorptions. This bacterial-specific and efficient capture of PM1 0.6B MS is attributed to its strong interactions with teichoic acids in MRSA (Ka: 1.8 × 105 M-1) rather than acting with phospholipids of mammalian cells. Unlike the present resin-based adsorbent, for example, heparin-modified polyethylene in the only commercial Seraph® 100, PM1 0.6B MS kills adsorbed bacteria within 1 h and can be reused by simple treatment. Meanwhile, PM1 0.6B MS also shows good hemocompatibility and longer thrombin activation time to reduce the risk of thrombosis and hemolysis. In vivo experiments further confirm the abilities of PM1 0.6B MS to prevent inflammation by removing bacteria. This adsorbent is a promising candidate for early treating life-threatening bloodstream infections, potentially preventing bacteremia and subsequent organ damage.

Activated platelet membrane vesicles for broad-spectrum bacterial pulmonary infections management

The development of new antibiotics has lagged behind the rapid evolution of bacterial resistance, prompting the exploration of alternative antimicrobial strategies. Host-directed therapy (HDT) has emerged as a promising approach by harnessing innate immune system's natural defense mechanisms, which reduces reliance on antibiotics, and mitigates the development of resistance. Building on the important role of platelets in host immunity, activated platelet membrane vesicles (PLTv) are developed here as a host-directed therapy for broad-spectrum antibacterial infection management, leveraging several key mechanisms of action. PLTv neutralizes bacterial toxins, thereby reducing cytotoxicity. The presence of platelet receptors on PLTv enables them to act as decoys, binding bacteria through receptor interactions and facilitating their phagocytosis by neutrophils and macrophages. Additionally, PLTv bound to bacteria promote the formation of neutrophil extracellular traps (NETs), enhancing the immune system's ability to trap and kill bacteria. In mouse models of pulmonary infections caused by the Methicillin-resistant Staphylococcus aureus, P. aeruginosa, and A. baumannii, administration of PLTv significantly reduces bacterial counts in the lungs and protects against mortality. Taken together, the present work highlights PLTv as a promising host-directed therapy for combating broad-spectrum pulmonary drug-resistant bacterial infections, leveraging their ability to neutralize toxins, act as decoys, promote phagocytosis, and facilitate NETs formation.

Single or double lipid-modified ultra-short antimicrobial peptides for treating infections caused by resistant bacteria

Unmodified ultra-short antimicrobial peptides (AMPs) have difficulty attaining high antimicrobial activity and low toxicity concurrently. Our previous studies have shown that single-site lipid modification can enhance the antimicrobial activity of AMPs. However, research on multi-site modification is scarce. This study designed and synthesized a series of single/double-site lipid-modified ultra-short AMPs. Particularly, the new single-site lipid-modified AMP C12 (C12-KKWW-NH2) and double-site lipid-modified AMP DC8 [(C8)2-KKKWW-NH2] showed high bacterial membrane selectivity and presented high stability. It is worth noting that C12 and DC8 exert excellent antibacterial effects on clinically resistant bacteria and have an extremely low resistance tendency. When combined with conventional antibiotics, they show synergistic antibacterial activity against resistant bacteria and curb the resistance of the antibiotics. Additionally, the novel ultra-short AMPs reveal non-receptor-mediated membrane bactericidal mechanisms and can kill the tested bacteria rapidly. Moreover, both C12 and DC8 have high antibacterial activity and low toxicity in vivo. These results suggest that both single-site and multi-site lipid modifications can produce highly efficient AMPs.

Synchronous Sterilization and Immunoreaction Termination for Corneal Transparency Protection in Treating Pseudomonas aeruginosa Induced Bacterial Keratitis

In the treatment of infectious keratitis, therapeutic strategies often prioritize enhancing bactericidal efficacy. However, endotoxins released from Gram-negative bacteria cause inflammatory reaction, leading to corneal structural damage and scar formation. Given that polymyxin B (PMB) can bind and neutralize lipopolysaccharide (LPS), this study employs large-pore mesoporous silica nanoparticles (lMSNs) grafted with PMB as carriers for cationic antibacterial carbon quantum dots (CQDs) to prepare CQD@lMSN-PMB, which enables synchronous sterilization and endotoxin neutralization. In the acidic infectious microenvironment, the accelerated release of CQDs eliminates 99.88% bacteria within 2 h, effectively substituting immune mediated sterilization. Notably, CQD@lMSN-PMB exhibits exceptional LPS neutralization performance (2.22 µg LPS/mg CQD@lMSN-PMB) due to its high specific surface area. In an infectious keratitis model, inflammation subsides significantly within the first day of CQD@lMSN-PMB intervention and is completely resolved by day 3. By day 2, interleukin-1β, interleukin-6 and tumor necrosis factor-α in CQD@lMSN-PMB group decrease by 86.99%, 91.15%, and 77.56%, respectively, compared to the CQDs-only sterilization group. Ultimately, corneal integrity and transparency are preserved, with suppressed expressions of fibrosis-related factors including matrix metalloproteinase 9, transforming growth factor-β and α-smooth muscle actin. Therefore, this synchronous sterilization and endotoxin neutralization strategy outperforms monotherapy strategies focused solely on sterilization or endotoxin neutralization.

Laser-assisted thermoelectric-enhanced hydrogen peroxide biosensors based on Ag2Se nanofilms for sensitive detection of bacterial pathogens

Thermoelectric (TE) materials can convert the heat produced during biochemical reactions into electrical signals, enabling the self-powered detection of biomarkers. In this work, we design and fabricate a simple Ag2Se nanofilm-based TE biosensor to precisely quantify hydrogen peroxide (H2O2) levels in liquid samples. A chemical reaction involving horseradish peroxidase, ABTS and H2O2 in the specimens produces a photothermal agent-ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) free radical, which triggers the heat fluctuations at the TE sensor through the photo-thermal effect, eventually enabling the sensing of H2O2. Consequently, the constructed sensor can achieve a detection limit of 0.26 μM by a three-leg TE device design. Further investigations suggest that the application of our TE sensor can be extended in testing H2O2 in beverages (including milk, soda water, and lemonade) and evaluating the load of bacterial pathogens relevant to dental diseases and infections including Streptococcus sanguinis and Methicillin-resistant Staphylococcus aureus with high analytical accuracy. This strategy utilizes the combination of high thermoelectric performance with chemical reactions to realize a straightforward and accurate biomarker detection method, making it suitable for applications in medical diagnostics, personalized health monitoring, and the food industry.

Methicillin-Resistant Staphylococcus aureus T144: A Hypervirulent Model Strain for Infection Models

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) presents a major public health challenge due to its multidrug resistance and high virulence. Developing representative model strains is crucial for systematically assessing pathogenesis and antimicrobial therapies. Methods: The highly virulent MRSA strain T144, isolated from pigs, was characterized through whole-genome sequencing and antimicrobial susceptibility testing. Infection models were successfully established in Galleria mellonella and mice to evaluate virulence. A mouse lung infection model was specifically developed to assess bacterial load dynamics, immune responses, and the efficacy of vancomycin treatment. Results: MRSA T144 demonstrated broad-spectrum antibiotic resistance and high mortality rates in both Galleria mellonella and mouse models. Whole-genome sequencing identified multiple virulence-associated genes, including hemolysins and enterotoxins. The concentration of 7 × 108 CFUs was optimized for establishing the mouse lung infection model. In the mouse lung infection model, MRSA T144 demonstrated rapid bacterial proliferation within the first 24 h, followed by a slower growth rate. Significant changes in immune markers were observed, with elevated levels of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-17a, TNF-α) and decreased IL-10 levels. Vancomycin treatment significantly improved survival rates and reduced bacterial load, confirming the model's utility for antimicrobial efficacy studies. Conclusions: The successful establishment of MRSA T144 infection models provides a robust platform for investigating bacterial dynamics, immune responses, and antimicrobial efficacy against highly virulent MRSA strains. These findings highlight the potential of MRSA T144 as a valuable model for developing novel therapeutic strategies.

Chitosan and gelatin based sprayable hydrogels incorporating photothermal and long-acting antibiotic sterilization for infected wound management with shape adaptability

Severe skin damage resulting from acute trauma is often accompanied by uncontrolled bleeding, microbial infections, and delayed wound healing. Herein, multifunctional sprayable hydrogels (CT-CS-ZIF@CIP Gel) were developed for wound management by incorporating antibacterial nanoplatforms (CT-CS-ZIF@CIP) into photocurable gels consisting of chitosan methacrylate and gallic acid grafted gelatin. The nanoplatform was initially constructed by sequentially loading Cu2Se (CS) and ciprofloxacin-decorated zeolitic imidazolate framework-8 (ZIF@CIP) onto Cu-doped Ti MOF (CT), in which CS served as a photothermal agent, ZIF enabled pH-responsive release of CIP, and CT acted as carriers for CS and ZIF@CIP. The hydrogel precursor can be sprayed onto wound surface and photocured quickly, allowing hydrogel to fit the wound shape and form a protective barrier onsite. The resultant hydrogel exhibited excellent hemostatic ability, adhesion properties, cytocompatibility and toxin adsorption capacity. By integrating CS for short-term photothermal therapy with CIP for long-acting chemotherapy, the CT-CS-ZIF@CIP Gel demonstrated 100 % sterilization of three bacterial strains. Furthermore, moderate release of zinc and copper ions promoted wound healing. The therapeutic efficacy of hydrogel was validated in an infected cutaneous mouse model. Overall, this work presents a versatile sprayable hydrogel that can be flexibly applied to irregular dynamic wounds for safe and effective wound management.

Self-assembling peptide with dual function of cell penetration and antibacterial as a nano weapon to combat intracellular bacteria

Intracellular bacterial infections and antimicrobial resistance are threatening global public health systems. Antimicrobial peptides are a potential solution to combat bacterial resistance, but the design of self-assembled nanopeptides with dual functions of cell penetration and antibacterial properties to combat intracellular bacteria remains a challenge. Here, we propose a strategy to develop self-assembled nanopeptides with dual functions through the chimerization of self-assembled core, hydrophobic motif, and cell-permeable unit. The optimal nanopeptides, F3FT and N3FT, exhibited potent antibacterial activity and excellent biocompatibility. Crucially, F3FT and N3FT are able to efficiently penetrate cells and eliminate intracellular bacteria and sniping inflammation. Moreover, F3FT and N3FT kill bacteria mainly by disrupting bacterial cell membranes and inducing excessive accumulation of reactive oxygen species. F3FT and N3FT have exhibited good safety and potent therapeutic potential in vivo. This scheme of constructing nanopeptides through multifunctional domains design provides a paradigm for dealing with escalating of intracellular bacteria and antimicrobial resistance.

Structure-Guided Development of ClpP Agonists with Potent Therapeutic Activities against Staphylococcus aureus Infection

Peritonitis caused by Staphylococcus aureus poses a severe threat to patients with end-stage renal failure. Treating multidrug-resistant S. aureus infections requires the use of antibiotics with diverse mechanisms of action. Caseinolytic protease P (ClpP) is a promising antibacterial target; however, selective activation of S. aureus ClpP (SaClpP) over human ClpP (HsClpP) remains challenging. We previously identified (R)-ZG197 as a selective SaClpP agonist, but its potency was suboptimal. Herein, we develop (R)-ZG197 analogs through a structure-guided approach and examine their structure-activity relationships. Notably, ZY39 demonstrates improved activation of SaClpP and superior binding affinity. Interestingly, while ZY39 facilitates the enzymatic hydrolysis of SaClpP and HsClpP in vitro, it does not target HsClpP in cellular environments. Furthermore, ZY39 effectively inhibits the growth of multidrug-resistant S. aureus strains and shows excellent therapeutic efficacy in a murine model of peritonitis. These findings highlight ZY39 as a promising SaClpP agonist for combating staphylococcal infections.

A Conjugated Oligomer with Drug Efflux Pump Inhibition and Photodynamic Therapy for Synergistically Combating Resistant Bacteria

High expression of drug efflux pump makes antibiotics ineffective against bacteria, leading to drug-resistant strains and even the emergence of "superbugs". Herein, we design and synthesize a dual functional o-nitrobenzene (NB)-modified conjugated oligo-polyfluorene vinylene (OPFV) photosensitizer, OPFV-NB, which can depress efflux pump activity and also possesses photodynamic therapy (PDT) for synergistically overcoming drug-resistant bacteria. Upon light irradiation, the OPFV-NB can produce aldehyde active groups to covalently bind outer membrane proteins, such as tolerant colicin (TolC), blocking drug efflux of bacteria. The minimum inhibitory concentration of antibiotic model chloramphenicol (CHL) is reduced about 64 times, significantly resensitizing drug-resistant bacteria to antibiotics. Also, the probe can produce highly efficient reactive oxygen species (ROS) under light irradiation. Consequently, the unimolecular OPFV-NB-based system demonstrates insusceptibility to antibiotic resistance while maintaining significant antimicrobial effects (100%) against drug-resistant bacteria. More importantly, in vivo assays corroborate that the combined system greatly accelerates wound healing by eradicating the bacterial population, dampening inflammation, and promoting angiogenesis. Overall, the OPFV-NB not only counteracts antibiotic resistance but also holds tremendous PDT efficiency, which provides a promising therapeutic strategy for combating drug-resistant bacteria and treating bacteria-infected wounds.

Natural agents derived Pickering emulsion enabled by silica nanoparticles with enhanced antibacterial activity against drug-resistant bacteria

The emergence of antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) has become a global health challenge due to the overuse of antibiotics. Natural substances including enzymes and essential oils have shown great potential as alternative treatment options. However, the combinational use of these natural agents remains challenging due to the denaturation of enzymes upon direct contact with oil. In this study, we report the design of a Pickering emulsion containing two natural antibacterial agents, lysozyme and tea tree oil, stabilized by fractal silica nanoparticles. In this design, the enzyme activity is kept and the volatility problem of tea tree oil is mitigated. Due to synergistic bacterial cell wall digestion and membrane disruption functions, potent bactericidal efficacy in vitro against drug-resistant bacteria is achieved. The therapeutic potential is further demonstrated in a wound healing model with drug-resistant bacteria infection, better than a synthetic antibiotic, Ampicillin. This study opens new avenues for the development of natural product-based antimicrobial treatments with promising application potential.

Recent advances in peptoids as promising antimicrobial agents to target diverse microbial species

The emergence of multidrug-resistant microbial species has become a global health concern, calling for novel antimicrobial agents. Peptoids, a class of synthetic peptidomimetics with unique structural properties, exhibit antimicrobial activity against a broad-spectrum of microbes, in addition to their stability to enzymatic degradation, selectivity, and relative ease of synthesis. Thus, peptoids have great potential in combating various drug-resistant pathogenic microbes. This review provides a comprehensive analysis of the recent advances in utilizing peptoids as effective antimicrobial agents against a wide range of bacteria, fungi, viruses, and parasites. In addition, some of the synthetic strategies and antimicrobial mechanisms are discussed. The imperfections of antimicrobial peptoids and the defects in current antimicrobial peptoids research are pointed out and promising directions for future development in peptoids are highlighted, to pave the way for innovating better antimicrobial peptoids to address the challenges posed by multidrug-resistant microbial species.

Intrinsic antimicrobial resistance: Molecular biomaterials to combat microbial biofilms and bacterial persisters

The escalating rise in antimicrobial resistance (AMR) coupled with a declining arsenal of new antibiotics is imposing serious threats to global public health. A pervasive aspect of many acquired AMR infections is that the pathogenic microorganisms exist as biofilms, which are equipped with superior survival strategies. In addition, persistent and recalcitrant infections are seeded with bacterial persister cells at infection sites. Together, conventional antibiotic therapeutics often fail in the complete treatment of infections associated with bacterial persisters and biofilms. Novel therapeutics have been attempted to tackle AMR, biofilms, and persister-associated complex infections. This review focuses on the progress in designing molecular biomaterials and therapeutics to address acquired and intrinsic AMR, and the fundamental microbiology behind biofilms and persisters. Starting with a brief introduction of AMR basics and approaches to tackling acquired AMR, the emphasis is placed on various biomaterial approaches to combating intrinsic AMR, including (1) semi-synthetic antibiotics; (2) macromolecular or polymeric biomaterials mimicking antimicrobial peptides; (3) adjuvant effects in synergy; (4) nano-therapeutics; (5) nitric oxide-releasing antimicrobials; (6) antimicrobial hydrogels; (7) antimicrobial coatings. Particularly, the structure-activity relationship is elucidated in each category of these biomaterials. Finally, illuminating perspectives are provided for the future design of molecular biomaterials to bypass AMR and cure chronic multi-drug resistant (MDR) infections.

Discovery of novel dihydropyrrolidone-thiadiazole compound crosstalk between the YycG/F two-component regulatory pathway and cell membrane homeostasis to combat methicillin-resistant Staphylococcus aureus

The rapid emergence and spread of multidrug-resistant (MDR) Gram-positive pathogens present a significant challenge to global healthcare. Methicillin-resistant Staphylococcus aureus (MRSA) is a particular concern because of its high resistance to most antibiotics. Based on our previously reported chemical structure of compound 62, a series of novel derivatives were synthesized and evaluated for their antibacterial activities. We found that some of these derivatives displayed effective antibacterial activity against Gram-positive pathogens, with minimal cytotoxicity (CC50>100 μM) and hemolytic activity (HC50>200 μM). Among these derivatives, the minimum inhibitory concentration (MIC) of 62-7c against Gram-positive bacterial isolates ranged from 6.25 to 25 μM. This derivative also exhibited significant synergistic antibacterial effects with daptomycin both in vitro and in vivo, with an ability to eradicate planktonic and persister cells of MRSA. Additionally, 62-7c inhibited biofilm formation and eradicated mature biofilms of MRSA. Mechanistic studies revealed that 62-7c inhibited the YycG kinase activity and disrupted the cell membrane by binding to cardiolipin (CL), leading to cell death. Importantly, no development of drug resistance was observed even after 20 serial passages. Furthermore, 62-7c exhibited high biosafety and potent effectiveness in combating infections in both mouse pneumonia and mouse wound models infected with MRSA. Thus, our study revealed that 62-7c has the potential to serve as a novel antibacterial agent for treating MRSA infections.

Antibacterial activity of a silver-incorporated vancomycin-modified mesoporous silica against methicillin-resistant Staphylococcus aureus

Since conventional antibiotics are almost ineffective on methicillin-resistant Staphylococcus aureus (MRSA) strains, designing their antibacterial alternatives is necessary. Besides, the use of vancomycin is applied for specific detection of the bacteria. Silver-incorporated vancomycin-modified mesoporous silica nanoparticles (MSNs@Van@Ag NPs) were designed for detection and treatment of MRSA bacteria. Mesoporous silica nanoparticles (MSNs) were synthesized through the template method, modified with vancomycin, and finally incorporated with silver nanoparticles (Ag NPs). The MSNs@Van@Ag NPs with a homogenously spherical shape, average size of 50-100 nm, surface area of 955.8 m2/g, and thermal stability up to 200°C were successfully characterized. The amount of Ag incorporated into the MSNs@Van@Ag was calculated at 3.9 ppm and the release amount of Ag was received at 2.92 ppm (75%) after 100 h. The in vitro antibacterial susceptibility test showed the MIC of 100 μg mL-1 for MSNs@Van and 50 μg mL-1 for MSNs@Van@Ag, showing in vitro enhanced effect of Ag and vancomycin in the bactericidal process. An in vivo acute pneumonia model was performed and biochemical assays and pathological studies confirmed the nanomedicine's short-term safety for in vivo application. Cytokine assay using ELISA showed that MSN@Van@Ag causes a reduction of pro-inflammatory cytokines and bacterial proliferation leading to alleviation of inflammatory response.

Synergistic berberine chloride and Curcumin-Loaded nanofiber therapies against Methicillin-Resistant Staphylococcus aureus Infection: Augmented immune and inflammatory responses in zebrafish wound healing

BACKGROUND

Wound healing pivots on a finely orchestrated inflammatory cascade, critical for tissue repair. Chronic wounds, compounded by persistent inflammation and susceptibility to infection, pose formidable clinical challenges. Nanofiber dressings offer promising avenues for wound care, yet their interaction with inflammation and infection remains elusive. We aim to delineate the inflammatory cascade preceding wound closure and assess Cu@Bbc nanofibers' therapeutic efficacy in mitigating inflammation and combating infection. Their unique attributes suggest promise in modulating inflammation, fostering tissue regeneration, and preventing microbial colonization. Investigating the intricate interplay between nanofiber scaffolds, inflammation, and infection may unveil mechanisms of enhanced wound healing. Our findings could stimulate the development of tailored dressings, urgently needed for effective wound management amidst immune dysregulation, infection, and inflammation.

METHODS

In this investigation, we synthesized Cu@Bbc nanofibers, incorporating curcumin and berberine chloride, for wound healing applications. We evaluated their individual and combined antibacterial, anti-biofilm, and antioxidant activities, alongside binding affinity with pro-inflammatory cytokines through molecular docking. Morphological characterization was conducted via SEM, FTIR assessed functional groups, and wettability contact angle measured hydrophobic properties. The physical properties, including tensile strength, swelling behavior, and thermal stability, were evaluated using tensile testing, saline immersion method and thermogravimetric analysis. Biodegradability of the nanofibers was assessed through a soil burial test. Biocompatibility was determined via MTT assay, while wound healing efficacy was assessed with in vitro scratch assays. Controlled drug release and antibacterial activity against MRSA were examined, with in vivo assessment in a zebrafish model elucidating inflammatory responses and tissue remodeling.

RESULTS

In this study, the synergistic action of curcumin and berberine chloride exhibited potent antibacterial efficacy against MRSA, with significant anti-mature biofilm disruption. Additionally, the combination demonstrated heightened antioxidant potential. Molecular docking studies revealed strong binding affinity with pro-inflammatory cytokines, suggesting a role in expediting the inflammatory response crucial for wound healing. Morphological analysis confirmed nanofiber quality, with drug presence verified via FTIR spectroscopy. Cu@Bbc demonstrated higher tensile strength, optimal swelling behavior, and robust thermal stability as evaluated through tensile testing and thermogravimetric analysis. Additionally, the Cu@Bbc nanofiber showed enhanced biodegradability, as confirmed by the soil burial test. Biocompatibility assessments showed favorable compatibility, while in vitro studies demonstrated potent antibacterial activity. In vivo zebrafish experiments revealed accelerated wound closure, re-epithelialization, and heightened immune response, indicative of enhanced wound healing.

CONCLUSION

In summary, our investigation highlights the efficacy of Cu@Bbc nanofibers, laden with curcumin and berberine chloride, in displaying robust antibacterial and antioxidant attributes while also modulating immune responses and inflammatory cascades essential for wound healing. These results signify their potential as multifaceted wound dressings for clinical implementation.

Gellan gum-based multifunctional hydrogel with enduring sterilization and ROS scavenging for infected wound healing

The progression of severe skin injury healing can be easily impeded by bacterial infections and the resultant overproduction of reactive oxygen species (ROS) within the wound microenvironment. In this study, we developed a multifunctional antibacterial hydrogel by integrating gallium ion-tannic acid and polydopamine particles into gellan gum via a facile heat-cooling process. By harnessing the synergistic effects of polydopamine for short-term photothermal therapy and gallium ion for long-term chemotherapy, the hydrogel obtained shows outstanding antibacterial activities. Sustained release of gallium ion and tannic acid ensures a prolonged sterilization along with ROS-scavenging benefits. Moreover, this hydrogel demonstrates superior cytocompatibility, hemostatic properties, as well as capabilities including promoting cell migration, and adsorption to bacterial cells and toxin. The therapeutic efficacy of the hydrogel was validated using a mouse model of MRSA-induced cutaneous infections. Overall, this work introduces a straightforward yet highly efficient multifunctional hydrogel platform that combines synergetic antibacterial actions, ROS scavenging, and hemostasis to enhance the healing of bacteria-associated wounds.

Advancements of Porphyrin-Derived Nanomaterials for Antibacterial Photodynamic Therapy and Biofilm Eradication

The threat posed by antibiotic-resistant bacteria and the challenge of biofilm formation has highlighted the inadequacies of conventional antibacterial therapies, leading to increased interest in antibacterial photodynamic therapy (aPDT) in recent years. This approach offers advantages such as minimal invasiveness, low systemic toxicity, and notable effectiveness against drug-resistant bacterial strains. Porphyrins and their derivatives, known for their high molar extinction coefficients and singlet oxygen quantum yields, have emerged as crucial photosensitizers in aPDT. However, their practical application is hindered by challenges such as poor water solubility and aggregation-induced quenching. To address these limitations, extensive research has focused on the development of porphyrin-based nanomaterials for aPDT, enhancing the efficacy of photodynamic sterilization and broadening the range of antimicrobial activity. This review provides an overview of various porphyrin-based nanomaterials utilized in aPDT and biofilm eradication in recent years, including porphyrin-loaded inorganic nanoparticles, porphyrin-based polymer assemblies, supramolecular assemblies, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Additionally, insights into the prospects of aPDT is offered, highlighting its potential for practical implementation.

Carboxymethyl chitosan nanoparticle-modulated cationic hydrogels doped with copper ions for combating bacteria and facilitating wound healing

The simultaneous administration of antibacterial treatment and acceleration of tissue regeneration are crucial for the effective healing of infected wounds. In this work, we developed a facile hydrogel (PCC hydrogel) through coordination and hydrogen interactions by polymerizing acrylamide monomers in the presence of carboxymethyl chitosan nanoparticles and copper ions. The prepared PCC hydrogel demonstrated effective bacterial capture from wound exudation and exhibited a potent bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Furthermore, slow release of copper ions from the hydrogel facilitated wound healing by promoting cell migration, collagen deposition and angiogenesis. Additionally, the PCC hydrogel possessed excellent biocompatibility and hemostatic properties. The practical effectiveness of PCC hydrogel in addressing bacterial infections and facilitating wound healing was verified using a mouse model of MRSA-induced wound infections. Overall, this work presents a simple yet efficient multifunctional hydrogel platform that integrates antibacterial activity, promotion of wound healing, and hemostasis for managing bacteria-associated wounds.

Mimics of Host Defense Peptides Derived from Dendronized Polylysines for Antibacterial and Anticancer Therapy

Bacteria in tumor microenvironments promote carcinogenesis and trigger complications, suggesting the significance of intervening in bacterial growth in cancer treatment. Here, dendrimer-derived mimics (DMs) of host defense peptides (HDPs) were designed for antibacterial and anticancer therapy, which feature a dendronized polylysine core and polycaprolactone arms. DMs displayed not only remarkable activities against Staphylococcus aureus and human lung cancer cells, but also exceptional selectivity. The membranolytic mechanism revealed by morphology analysis explained their low susceptibility to induce resistance. Further, the optimized DM inhibited tumor growth in the subcutaneous tumor model when administered via intraperitoneal injection and exhibited negligible toxicity to tissues. Overall, we combined the superiority of dendrimers and the mechanism from HDPs to design agents with dual antibacterial and anticancer activities that possess great potential for clinical oncology therapy.

High Therapeutic Index α-Helical AMPs and Their Therapeutic Potential on Bacterial Lung and Skin Wound Infections

Antimicrobial peptides (AMPs) possess strong antibacterial activity and low drug resistance, making them ideal candidates for bactericidal drugs for addressing the issue of traditional antibiotic resistance. In this study, a template (G(XXKK)nI, G = Gly; X = Leu, Ile, Phe, or Trp; n = 2, 3, or 4; K = Lys; I = Ile.) was employed for the devised of a variety of novel α-helical AMPs with a high therapeutic index. The AMP with the highest therapeutic index, WK2, was ultimately chosen following a thorough screening process. It demonstrates broad-spectrum and potent activity against both standard and multidrug-resistant bacteria, while also showing low hemolysis and rapid and efficient time-kill kinetics. Additionally, WK2 exhibits excellent efficacy in treating mouse models of Klebsiella pneumonia-induced lung infections and methicillin-resistant Staphylococcus aureus (MRSA)-induced skin wound infections while demonstrating good safety profiles in vivo. In conclusion, the template-based design methodology for novel AMPs with high therapeutic indices offers new insights into addressing antibiotic resistance problems. WK2 represents a promising antimicrobial agent.

Assessing the Influence of Urine pH on the Efficacy of Ciprofloxacin and Fosfomycin in Immunocompetent and Immunocompromised Murine Models of Escherichia coli and Klebsiella pneumoniae Infection in the Lower Urinary Tract

In vitro studies have suggested that acidic pH may reduce and increase the efficacy of ciprofloxacin and fosfomycin, respectively, when used to treat Escherichia coli and Klebsiella pneumoniae infections. We assessed the effects of acidic, neutral, and alkaline urine pH on the efficacy of optimized ciprofloxacin and fosfomycin dosages in UTI murine model of E. coli and K. pneumoniae. Immunocompetent and immunocompromised mice with adjusted urine pH were inoculated with E. coli and K. pneumoniae strains, and the efficacy was assessed based on the bacterial concentrations in tissues and fluids at 72 h, with respect to untreated controls. At acidic urine pH, both antimicrobials were effective, achieving similar reductions in E. coli concentrations in the kidneys in immunocompetent and immunocompromised mice and in K. pneumoniae in immunocompetent mice. At a neutral urine pH, both therapies reduced the presence of E. coli in the kidneys of immunocompetent mice. However, in immunocompromised mice, antimicrobials were ineffective at treating E. coli infection in the kidneys at a neutral urine pH and showed reduced efficacy against K. pneumoniae at both acidic and neutral urine pH. The results showed no correlation between urine pH and antimicrobial efficacy, suggesting that the reduced effectiveness is associated with the animals' immunocompetence status.

Fluoroamphiphilic polymers exterminate multidrug-resistant Gram-negative ESKAPE pathogens while attenuating drug resistance

ESKAPE pathogens are a panel of most recalcitrant bacteria that could "escape" the treatment of antibiotics and exhibit high incidence of drug resistance. The emergence of multidrug-resistant (MDR) ESKAPE pathogens (particularly Gram-negative bacteria) accounts for high risk of mortality and increased resource utilization in health care. Worse still, there has been no new class of antibiotics approved for exterminating the Gram-negative bacteria for more than 50 years. Therefore, it is urgent to develop novel antibacterial agents with low resistance and potent killing efficacy against Gram-negative ESKAPE pathogens. Herein, we present a class of fluoropolymers by mimicking the amphiphilicity of cationic antimicrobial peptides. Our optimal fluoroamphiphilic polymer (PD45HF5) displayed selective antimicrobial ability for all MDR Gram-negative ESAKPE pathogens, low resistance, high in vitro cell selectivity, and in vivo curative efficacy. These findings implied great potential of fluoroamphiphilic cationic polymers as promising antibacterial agents against MDR Gram-negative ESKAPE bacteria and alleviating antibiotic resistance.

Helicity-directed recognition of bacterial phospholipid via radially amphiphilic antimicrobial peptides

The fundamental differences in phospholipids between bacterial and mammalian cell membranes present remarkable opportunities for antimicrobial design. However, it is challenging to distinguish bacterial anionic phospholipid phosphatidylglycerol (PG) from mammalian anionic phosphatidylserine (PS) with the same net charge. Here, we report a class of radially amphiphilic α helix antimicrobial peptides (RAPs) that can selectively discriminate PG from PS, relying on the helix structure. The representative RAP, L10-MMBen, can direct the rearrangement of PG vesicles into a lamellar structure with its helix axis parallel to the PG membrane surface. The helical structure imparts both the thermodynamic and kinetic advantages of L10-MMBen/PG assembly, and the hiding of hydrophobic regions in RAPs is crucial for PG recognition. L10-MMBen exhibits high selectivity against bacteria depending on PG recognition, showing low in vivo toxicity and significant treatment efficacy in mice infection models. Our study introduces a helicity-direct bacterial phospholipid recognition paradigm for designing highly selective antimicrobial peptides.

Amino Acid-Conjugated Polymer-Silver Bromide Nanocomposites for Eradicating Polymicrobial Biofilms and Treating Burn Wound Infections

The rise in antimicrobial resistance, the increasing occurrence of bacterial, and fungal infections, and the challenges posed by polymicrobial biofilms necessitate the exploration of innovative therapeutic strategies. Silver-based antimicrobials have garnered attention for their broad-spectrum activity and multimodal mechanisms of action. However, their effectiveness against single-species or polymicrobial biofilms remains limited. In this study, we present the fabrication of polymer-silver bromide nanocomposites using amino acid conjugated polymers (ACPs) through a green and water-based in situ technique. The nanocomposite architecture facilitated prolonged and controlled release of the active components. Remarkably, the nanocomposites exhibited broad-spectrum activity against multidrug-resistant (MDR) human pathogenic bacteria (MIC = 2-16 μg/mL) and fungi (MIC = 1-8 μg/mL), while displaying no detectable toxicity to human erythrocytes (HC50 > 1024 μg/mL). In contrast to existing antimicrobials and silver-based therapies, the nanocomposite effectively eradicated bacterial, fungal, and polymicrobial biofilms, and prevented the development of microbial resistance due to their membrane-active properties. Furthermore, the lead polymer-silver bromide nanocomposite demonstrated a 99% reduction in the drug-resistant Pseudomonas aeruginosa burden in a murine model of burn wound infection, along with excellent in vivo biocompatibility.

AI-guided few-shot inverse design of HDP-mimicking polymers against drug-resistant bacteria

Host defense peptide (HDP)-mimicking polymers are promising therapeutic alternatives to antibiotics and have large-scale untapped potential. Artificial intelligence (AI) exhibits promising performance on large-scale chemical-content design, however, existing AI methods face difficulties on scarcity data in each family of HDP-mimicking polymers (<102), much smaller than public polymer datasets (>105), and multi-constraints on properties and structures when exploring high-dimensional polymer space. Herein, we develop a universal AI-guided few-shot inverse design framework by designing multi-modal representations to enrich polymer information for predictions and creating a graph grammar distillation for chemical space restriction to improve the efficiency of multi-constrained polymer generation with reinforcement learning. Exampled with HDP-mimicking β-amino acid polymers, we successfully simulate predictions of over 105 polymers and identify 83 optimal polymers. Furthermore, we synthesize an optimal polymer DM0.8iPen0.2 and find that this polymer exhibits broad-spectrum and potent antibacterial activity against multiple clinically isolated antibiotic-resistant pathogens, validating the effectiveness of AI-guided design strategy.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

Unique aminothiazolyl coumarins as potential DNA and membrane disruptors towards Enterococcus faecalis

Aminothiazolyl coumarins as potentially new antimicrobial agents were designed and synthesized in an effort to overcome drug resistance. Biological activity assay revealed that some target compounds exhibited significantly inhibitory efficiencies toward bacteria and fungi including drug-resistant pathogens. Especially, aminothiazolyl 7-propyl coumarin 8b and 4-dichlorobenzyl derivative 11b exhibited bactericidal potential (MBC/MIC = 2) toward clinically drug-resistant Enterococcus faecalis with low cytotoxicity to human lung adenocarcinoma A549 cells, rapidly bactericidal effects and no obvious bacterial resistance development against E. faecalis. The preliminary antibacterial action mechanism studies suggested that compound 11b was able to disturb E. faecalis membrane effectively, and interact with bacterial DNA isolated from resistant E. faecalis through noncovalent bonds to cleave DNA, thus inhibiting the growth of E. faecalis strain. Further molecular modeling indicated that compounds 8b and 11b could bind with SER-1084 and ASP-1083 residues of gyrase-DNA complex through hydrogen bonds and hydrophobic interactions. Moreover, compound 11b showed low hemolysis and in vivo toxicity. These findings of aminothiazolyl coumarins as unique structural scaffolds might hold a large promise for the treatments of drug-resistant bacterial infection.

Biomimetic protein structural transitions regulate activation and inhibition of the broad-spectrum bactericidal activity of cationic nanoparticles

The development of cationic polymers as alternative materials to antibiotics necessitates addressing the challenge of balancing their antimicrobial activity and toxicity. Here we propose a precise switching strategy inspired by biomimetic voltage-gated ion channels, enabling controlled activation and inhibition of cationic antimicrobial functions through protein conformational transitions in diverse physiological environments. Following thermodynamic studies on the specific recognition between mannose end groups on polycations and concanavalin A (ConA), we synthesized a type of ConA-polycation nanoparticle. The nanoparticle was inhibited under neutral conditions, with cationic moieties shielded by ConA's β-sheet. This shielding suppresses their antimicrobial activity, thereby ensuring satisfactory biocompatibility. In mildly acidic environments, however, the transition of a portion of ConA to an α-helix conformation exposed cations at the particle periphery, activating antibacterial functionality. Compared to inhibited nanoparticles, those in the activated state exhibited a 32-256 times reduction in the minimum bactericidal concentration against bacteria and fungi (2-16 µg/mL). In a murine acute pulmonary infection model, intravenous administration of inhibited nanoparticles effectively reduced bacterial counts by 4-log within 12 h. The biomimetic design, regulating cationic antimicrobial functionality through the alteration in protein secondary structure, significantly retards bacterial resistance development, holding great promise for intelligent antimicrobial materials. STATEMENT OF SIGNIFICANCE: Cationic antimicrobial polymers exhibit advantages distinct from antibiotics due to their lower propensity for resistance development. However, the presence of cationic moieties also poses a threat to healthy cells and tissues, significantly constraining their potential for clinical applications. To address this challenge, we propose a biomimetic strategy that mimics voltage-gated ion channels to activate the antimicrobial functionality of cations selectively in bacterial environments through the conformational transitions of proteins between β-sheets and α-helices. In healthy tissues, the antimicrobial functionality is inhibited, ensuring satisfactory biocompatibility. Antimicrobial cationic materials capable of intelligent switching between an activated state and an inhibited state in response to environmental changes offer an effective strategy to prevent the development of resistance and mitigate potential side effects.

A Hemoglobin Bionics-Based System for Combating Antibiotic Resistance in Chronic Diabetic Wounds via Iron Homeostasis Regulation

Owing to the increased tissue iron accumulation in patients with diabetes, microorganisms may activate high expression of iron-involved metabolic pathways, leading to the exacerbation of bacterial infections and disruption of systemic glucose metabolism. Therefore, an on-demand transdermal dosing approach that utilizes iron homeostasis regulation to combat antimicrobial resistance is a promising strategy to address the challenges associated with low administration bioavailability and high antibiotic resistance in treating infected diabetic wounds. Here, it is aimed to propose an effective therapy based on hemoglobin bionics to induce disturbances in bacterial iron homeostasis. The preferred "iron cargo" is synthesized by protoporphyrin IX chelated with dopamine and gallium (PDGa), and is delivered via a glucose/pH-responsive microneedle bandage (PDGa@GMB). The PDGa@GMB downregulates the expression levels of the iron uptake regulator (Fur) and the peroxide response regulator (perR) in Staphylococcus aureus, leading to iron nutrient starvation and oxidative stress, ultimately suppressing iron-dependent bacterial activities. Consequently, PDGa@GMB demonstrates insusceptibility to genetic resistance while maintaining sustainable antimicrobial effects (>90%) against resistant strains of both S. aureus and E. coli, and accelerates tissue recovery (<20 d). Overall, PDGa@GMB not only counteracts antibiotic resistance but also holds tremendous potential in mediating microbial-host crosstalk, synergistically attenuating pathogen virulence and pathogenicity.

Histatin 5-Inspired Short-Chain Peptides Selectively Combating Pathogenic Fungi with Multifaceted Mechanisms

Short-chain antifungal peptides (AFPs) inspired by histatin 5 have been designed to address the problem of antifungal drug resistance. These AFPs demonstrate remarkable antifungal activity, with a minimal inhibitory concentration as low as 2 µg mL-1. Notably, these AFPs display a strong preference for targeting fungi rather than bacteria and mammalian cells. This is achieved by binding the histidine-rich domains of the AFPs to the Ssa1/2 proteins in the fungal cell wall, as well as the reduced membrane-disrupting activity due to their low amphiphilicity. These peptides disrupt the nucleus and mitochondria once inside the cells, leading to reactive oxygen species production and cell damage. In a mouse model of vulvovaginal candidiasis, the AFPs demonstrate not only antifungal activity, but also promote the growth of beneficial Lactobacillus spp. This research provides valuable insights for the development of fungus-specific AFPs and offers a promising strategy for the treatment of fungal infectious diseases.

Degradable Microneedle Patch with Photothermal-Promoted Bacteria-Infected Wound Healing and Microenvironment Remodeling

Bacteria-infected wound healing is one of the most challenging issues in health management that is attracting worldwide concerns. Despite great achievements with antibiotics, emergence of antibiotic-resistance retarded the wound healing process and also led to severe outcomes. Exploration of novel antibiotics together with amelioration of wound healing efficacy is desirable. Herein, a degradable microneedle patch (AAZH@MNs) was fabricated through incorporating near-infrared light responsive photothermal agents for sustained bacteria killing and prevention of biofilm formation. In addition, the antibacterial microneedle patch could even remold the microenvironment of bacteria-infected wounds through an antibacterial effect, significantly facilitating the wound healing process.

A multifunctional thermosensitive hydrogel based on phototherapy for promoting the healing of dental extraction wounds

Post-extraction wound infections are a common complication of dental extractions. More specifically, infection in the alveolar socket after tooth extraction accelerates the resorption and destruction of the alveolar bone, and ultimately affects the final restoration results. Currently, the main clinical treatment approaches applied to the socket after tooth extraction include mechanical wound debridement, chemical rinses (e.g., chlorhexidine), filling of the extraction socket with absorbent gelatin sponges, and the systemic application of antibiotics. However, these traditional treatment modalities have some limitations and their therapeutic effects are unsatisfactory. In this study, a phototherapeutic temperature-sensitive hydrogel material was constructed for injection using a tea polyphenol (TP)-modified poly-N-isopropylacrylamide (PNIPAM) hydrogel skeleton loaded with the photosensitiser indocyanine green (ICG). The resulting PNIPAM-TP/ICG system exhibited an excellent injectability and temperature-sensitive properties. In addition, it stopped haemorrhaging and acted as a wound astringent. The hydrogel steadily released ICG into the oral environment to exert photothermal/photodynamic effects along with synergistic antibacterial and anti-inflammatory properties when combined with tea polyphenols. In vivo experiments demonstrated that the application of PNIPAM-TP/ICG to infected dental extraction wounds in rats rapidly stopped the bleeding and accelerated wound healing. Overall, this study describes a drug-loaded, temperature-sensitive hydrogel for the treatment of open wound infections, and shows promise as a reference for the treatment of tooth extraction wounds.

Innovative peptide architectures: advancements in foldamers and stapled peptides for drug discovery

INTRODUCTION

Peptide foldamers play a critical role in pharmaceutical research and biomedical applications. This review highlights recent (post-2020) advancements in novel foldamers, synthetic techniques, and their applications in pharmaceutical research.

AREAS COVERED

The authors summarize the structures and applications of peptide foldamers such as α, β, γ-peptides, hydrocarbon-stapled peptides, urea-type foldamers, sulfonic-γ-amino acid foldamers, aromatic foldamers, and peptoids, which tackle the challenges of traditional peptide drugs. Regarding antimicrobial use, foldamers have shown progress in their potential against drug-resistant bacteria. In drug development, peptide foldamers have been used as drug delivery systems (DDS) and protein-protein interaction (PPI) inhibitors.

EXPERT OPINION

These structures exhibit resistance to enzymatic degradation, are promising for therapeutic delivery, and disrupt crucial PPIs associated with diseases such as cancer with specificity, versatility, and stability, which are useful therapeutic properties. However, the complexity and cost of their synthesis, along with the necessity for thorough safety and efficacy assessments, necessitate extensive research and cross-sector collaboration. Advances in synthesis methods, computational modeling, and targeted delivery systems are essential for fully realizing the therapeutic potential of foldamers and integrating them into mainstream medical treatments.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA-induced Sepsis and Chronic Wound Infection

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad-spectrum and low resistance tendency. Herein, a library of fluoro-lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non-fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co-assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA-induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug-resistant bacterial infections.

Nanomaterials with Enzyme-like Properties for Combatting Foodborne Pathogen Infections: Classifications, Mechanisms, and Applications in Food Preservation

During the transportation and storage of food, foodborne spoilage caused by bacterial and biofilm infection is prone to occur, leading to issues such as short shelf life, economic loss, and sensory quality instability. Therefore, the development of novel and efficient antibacterial agents capable of efficiently inhibiting bacteria throughout various stages of food processing, transportation, and storage is strongly recommended by researchers. The emergence of nanozymes is considered to be an effective candidate for inhibiting foodborne bacteria agents in the food industry. As potent antibacterial agents, nanozymes have the advantages of low cost, high stability, strong broad-spectrum antibacterial ability, and biocompatibility. Herein, we aim to summarize the classification status of various nanozymes. Furthermore, the general catalytic bacteriostatic mechanism of nanozymes against intracellular bacteria, planktonic bacteria, and biofilm activities are highlighted, mainly concerning the destruction of cell walls and/or membranes, reactive oxygen species regulation, HOBr/Cl generation, damage of intracellular components, and so forth. In particular, the review focuses on the pivotal role of nanozymes as antibacterial agents and delivery vehicles in the fields of food preservation applications. We look forward to the future prospects, especially in the field of food preservation, to promote broader applications based on antimicrobial nanozymes.

Staphylococcus haemolyticus: An updated review on nosocomial infections, antimicrobial resistance, virulence, genetic traits, and strategies for combating this emerging opportunistic pathogen

Staphylococcus haemolyticus, a key species of the Staphylococcus genus, holds significant importance in healthcare-associated infections, due to its notable resistance to antimicrobials, like methicillin, and proficient biofilms-forming capabilities. This coagulase-negative bacterium poses a substantial challenge in the battle against nosocomial infections. Recent research has shed light on Staph. haemolyticus genomic plasticity, unveiling genetic elements responsible for antibiotic resistance and their widespread dissemination within the genus. This review presents an updated and comprehensive overview of the clinical significance and prevalence of Staph. haemolyticus, underscores its zoonotic potential and relevance in the one health framework, explores crucial virulence factors, and examines genetics features contributing to its success in causing emergent and challenging infections. Additionally, we scrutinize ongoing studies aimed at controlling spread and alternative approaches for combating it.

Injectable Phage-Loaded Microparticles Effectively Release Phages to Kill Methicillin-Resistant Staphylococcus aureus

The increasing prevalence of bacterial multidrug antibiotic resistance has led to a serious threat to public health, emphasizing the urgent need for alternative antibacterial therapeutics. Lytic phages, a class of viruses that selectively infect and kill bacteria, offer promising potential as alternatives to antibiotics. However, injectable carriers with a desired release profile remain to be developed to deliver them to infection sites. To address this challenge, phage-loaded microparticles (Phage-MPs) have been developed to deliver phages to the infection site and release phages for an optimal therapeutic effect. The Phage-MPs are synthesized by allowing phages to be electrostatically attached onto the porous polyethylenimine-modified silk fibroin microparticles (SF-MPs). The high specific surface area of SF-MPs allows them to efficiently load phages, reaching about 1.25 × 1010 pfu per mg of microparticles. The Phage-MPs could release phages in a controlled manner to achieve potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Unlike the diffuse biodistribution of free phages post-intraperitoneal injection, Phage-MPs could continuously release phages to effectively boost the local phage concentration at the bacterial infection site after they are intraperitoneally injected into an abdominal MRSA-infected mouse model. In a mouse abdominal MRSA infection model, Phage-MPs significantly reduce the bacterial load in major organs, achieving an efficient therapeutic effect. Furthermore, Phage-MPs demonstrate outstanding biocompatibility both in vitro and in vivo. Overall, our research lays the foundation for a new generation of phage-based therapies to combat antibiotic-resistant bacterial infections.

Multifunctional fucoidan-loaded Zn-MOF-encapsulated microneedles for MRSA-infected wound healing

Infected wound healing remains a challenging task in clinical practice due to several factors: (I) drug-resistant infections caused by various pathogens, (II) persistent inflammation that hinders tissue regeneration and (III) the ability of pathogens to persist intracellularly and evade antibiotic treatment. Microneedle patches (MNs), recognized for their effecacious and painless subcutaneous drug delivery, could greatly enhance wound healing if integrated with antibacterial functionality and tissue regenerative potential. A multifunctional agent with subcellular targeting capability and contained novel antibacterial components, upon loading onto MNs, could yield excellent therapeutic effects on wound infections. In this study, we sythesised a zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) loaded with low molecular weight fucoidan (Fu) and further coating by hyaluronic acid (HA), obtained a multifunctional HAZ@Fu NPs, which could hinders Methicillin-resistant Staphylococcus aureus (MRSA) growth and promotes M2 polarization in macrophages. We mixed HAZ@Fu NPs with photocrosslinked gelatin methacryloyl (GelMA) and loaded it into the tips of the MNs (HAZ@Fu MNs), administered to mice model with MRSA-infected full-thickness cutaneous wounds. MNs are able to penetrate the skin barrier, delivering HAZ@Fu NPs into the dermal layer. Since cells within infected tissues extensively express the HA receptor CD44, we also confirmed the HA endows the nanoparticles with the ability to target MRSA in subcellular level. In vitro and in vivo murine studies have demonstrated that MNs are capable of delivering HAZ@Fu NPs deep into the dermal layers. And facilitated by the HA coating, HAZ@Fu NPs could target MRSA surviving at the subcellular level. The effective components, such as zinc ions, Fu, and hyaluronic acid could sustainably released, which contributes to antibacterial activity, mitigates inflammation, promotes epithelial regeneration and fosters neovascularization. Through the RNA sequencing of macrophages post co-culture with HAZ@Fu, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis reveals that the biological functionalities associated with wound healing could potentially be facilitated through the PI3K-Akt pathway. The results indicate that the synergistic application of HAZ@Fu NPs with biodegradable MNs may serve as a significant adjunct in the treatment of infected wounds. The intricate mechanisms driving its biological effects merit further investigation.

Repurposing cinacalcet suppresses multidrug-resistant Staphylococcus aureus by disruption of cell membrane and inhibits biofilm by targeting IcaR

BACKGROUND

MDR Staphylococcus aureus infections, along with the severity of biofilm-associated infections, continue to threaten human health to a great extent. It necessitates the urgent development of novel antimicrobial and antibiofilm agents.

OBJECTIVES

To reveal the mechanism and target of cinacalcet as an antibacterial and antimicrobial agent for S. aureus.

METHODS

Screening of non-antibiotic drugs for antibacterial and antibiofilm properties was conducted using a small-molecule drug library. In vivo efficacy was assessed through animal models, and the antibacterial mechanism was studied using quantitative proteomics, biochemical assays, LiP-SMap, BLI detection and gene knockout techniques.

RESULTS

Cinacalcet, an FDA-approved drug, demonstrated antibacterial and antibiofilm activity against S. aureus, with less observed development of bacterial resistance. Importantly, cinacalcet significantly improved survival in a pneumonia model and bacterial clearance in a biofilm infection model. Moreover, the antibacterial mechanism of cinacalcet mainly involves the destruction of membrane-targeted structures, alteration of energy metabolism, and production of reactive oxygen species (ROS). Cinacalcet was found to target IcaR, inhibiting biofilm formation through the negative regulation of IcaADBC.

CONCLUSIONS

The findings suggest that cinacalcet has potential for repurposing as a therapeutic agent for MDR S. aureus infections and associated biofilms, warranting further investigation.

Self-supporting noncovalent Choline Alginate/Tannic acid/Ag antibacterial films for strawberry preservation

Packaging materials with peculiar antibacterial properties can shield off and inhibit microorganism proliferation, thus achieving packaging goals such as fresh-keeping, good hygiene, and biosafety. Especially, antibacterial films made of biocompatible substances have received wide attentions, which could effectively extend the shelf life, enhance food security, and guarantee economic benefits. Herein, a self-supporting hybrid antibacterial film was prepared based on non-covalently linked choline hydroxide (ChOH) and alginic acid (HAlg). Then tannic acid (TA) and silver ions were added to improve the mechanical and antimicrobial properties of this hybrid film. The rich hydroxyl groups from TA not only form multiple hydrogen bonds with ChAlg, but can also in situ reduce silver ions to silver nanoparticles, which were confirmed with various characterizations. In addition, the quantitative antibacterial test proved that the antibacterial rate was significantly improved after adding silver ions, reaching >60 %. In an actual storage test, we found that choline cation (Ch+) captured in antibacterial film by electrostatic interaction could achieve sustained release, i.e. sustainable bacteriostasis, and keep strawberries fresh for 48 h at room temperature. This work offers a new strategy for preparing antibacterial films via non-covalent weak interactions, explored an alternative antibacterial film for food packaging applications.

Design, synthesis and antibacterial evaluation of low toxicity amphiphilic-cephalosporin derivatives

Global public health is facing a serious problem as a result of the rise in antibiotic resistance and the decline in the discovery of new antibiotics. In this study, two series of amphiphilic-cephalosporins were designed and synthesized, several of which showed good antibacterial activity against both Gram-positive and Gram-negative bacteria. Structure-activity relationships indicated that the length of the hydrophobic alkyl chain significantly affects the antibacterial activity against Gram-negative bacteria. The best compound 2d showed high activity against drug-susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MICs of 0.5 and 2-4 μg/mL, respectively. Furthermore, 2d remained active in complex mammalian body fluids and had a longer post-antibiotic effect (PAE) than vancomycin. Mechanism studies indicated that compound 2d lacks membrane-damaging properties and can target penicillin-binding proteins to disrupt bacterial cell wall structure, inhibit the metabolic activity and induce the accumulation of reactive oxygen species (ROS) in bacteria. Compound 2d showed minimal drug resistance and was nontoxic to HUVEC and HBZY-1 cells with CC50 > 128 μg/mL. These findings suggest that 2d is a promising drug candidate for treating bacterial infections.

Clinically Approved Ferric Maltol: A Potent Nanozyme with Added Effect for High-Efficient Catalytic Disinfection

Nanozyme has been proven to be an attractive and promising candidate to alleviate the current pressing medical problems. However, the unknown clinical safety and limited function beyond the catalysis of the most reported nanozymes cannot promise an ideal therapeutic outcome in further clinical application. Herein, we find that ferric maltol (FM), a clinically approved iron supplement synthesized through a facile scalable method, exhibits excellent peroxidase-like activity than natural horseradish peroxidase-like (HRP) and commonly reported Fe-based nanozymes, and also shows high antibacterial performance for methicillin-resistant Staphylococcus aureus (MRSA) elimination (100%) and wound disinfection. In addition, with added effects inherited from contained maltol, FM can accelerate skin barrier recovery. Therefore, the exploration of FM as a safe and desired nanozyme provides a timely alternative to current antibiotic therapy against drug-resistant bacteria.