Intrinsic Antibacterial Activity Research Articles

Pyridinium‐Yne Click Polymerization: A Facile Strategy toward Functional Poly(Vinylpyridinium Salt)s with Multidrug‐Resistant Bacteria Killing Ability

Polymeric materials with antibacterial properties hold great promise for combating multidrug‐resistant bacteria, which pose a significant threat to public health. However, the synthesis of most antibacterial polymers typically involves complicated and time‐consuming procedures. In this study, we demonstrate a simple and efficient strategy for synthesizing functional poly(vinylpyridinium salt)s via pyridinium‐yne click polymerization. This click polymerization could proceed with high atom economy under mild conditions without any external catalyst, yielding soluble and thermally stable poly(vinylpyridinium salt)s with satisfactory molecular weights and well‐defined structures in excellent yields. Additionally, the incorporation of luminescent units such as fluorene, tetraphenylethylene, and triphenylamine into the polymer backbone confers excellent aggregation‐enhanced emission properties upon the resulting polymers, rendering them suitable for bacterial staining. Moreover, the existence of pyridinium salt imparts intrinsic antibacterial activity against multidrug‐resistant bacteria to the polymers, enabling them to effectively inhibit wound bacterial infection and significantly expedite the healing process. This work not only provides an efficient method to prepare antibacterial polymers, but also opens up the possibility of various applications of polymers in healthcare and other antibacterial fields.

Pyridinium-Yne Click Polymerization: A Facile Strategy toward Functional Poly(Vinylpyridinium Salt)s with Multidrug-Resistant Bacteria Killing Ability.

Polymeric materials with antibacterial properties hold great promise for combating multidrug-resistant bacteria, which pose a significant threat to public health. However, the synthesis of most antibacterial polymers typically involves complicated and time-consuming procedures. In this study, we demonstrate a simple and efficient strategy for synthesizing functional poly(vinylpyridinium salt)s via pyridinium-yne click polymerization. This click polymerization could proceed with high atom economy under mild conditions without any external catalyst, yielding soluble and thermally stable poly(vinylpyridinium salt)s with satisfactory molecular weights and well-defined structures in excellent yields. Additionally, the incorporation of luminescent units such as fluorene, tetraphenylethylene, and triphenylamine into the polymer backbone confers excellent aggregation-enhanced emission properties upon the resulting polymers, rendering them suitable for bacterial staining. Moreover, the existence of pyridinium salt imparts intrinsic antibacterial activity against multidrug-resistant bacteria to the polymers, enabling them to effectively inhibit wound bacterial infection and significantly expedite the healing process. This work not only provides an efficient method to prepare antibacterial polymers, but also opens up the possibility of various applications of polymers in healthcare and other antibacterial fields.

Tannic acid-crosslinked gelatin composite microspheres adsorbed with CQAS or Ca2+ for rapid hemostasis

In the case of massive blood loss due to natural disasters and wars, timely and rapid hemostasis is of great significance to improve the survival rate of injured people. Nevertheless, uncontrolled, noncompressible, and irregular bleeding wounds remain a giant challenge for rapid hemostasis. In this study, the tannic acid-crosslinked gelatin was first obtained by Michael addition reaction, and then the tannic acid-crosslinked gelatin composite microspheres (TGMs) were prepared by the emulsion cross-linking method. TGMs could significantly improve the water absorption and hemostatic performance compared with single component gelatin microspheres (GMs). Increasing the water absorption ratio and introducing blood coagulation factors into composite materials are simple and effective strategies to enhance the hemostatic properties. Therefore, chitosan quaternary ammonium salt (CQAS) and Ca2+ were electrostatic adsorbed to obtain two kinds of functional TGMs, which were respectively CQAS-absorbed TGMs (T2GMs-CQAS) and calcium ion-absorbed TGMs (T2GMs-Ca2+). Notably, T2GMs-CQAS, and T2GMs-Ca2+ could absorb water rapidly within 3seconds, in addition, especially the water absorption ratio of T2GMs-CQAS could reach 2.95 times compared with GMs. Benefited from rapid water absorption, coagulation pathway activation, and red blood cells aggregation of T2GMs-CQAS and T2GMs-Ca2+, resulting in rapid blood coagulation in vitro. In addition, CQAS and Ca2+ provided strong and intrinsic antibacterial activity due to positive charge. Moreover, in the tail amputation and liver hemostatic models, T2GMs-CQAS and T2GMs-Ca2+ demonstrated superior hemostatic effects compared to commercial Yunnan Baiyao®. In conclusion, T2GMs-CQAS and T2GMs-Ca2+ have potential applications as hemostatic dressings in uncontrolled, noncompressible, and irregular bleeding wounds.

Arg-biodynamers as antibiotic potentiators through interacting with Gram-negative outer membrane lipopolysaccharides

Antimicrobial resistance is becoming more prominent day after day due to a number of mechanisms by microbes, especially the sophisticated biological barriers of bacteria, especially in Gram-negatives. There, the lipopolysaccharides (LPS) layer is a unique component of the outer leaflet of the outer membrane which is highly impermeable and prevents antibiotics from passing passively into the intracellular compartments. Biodynamers, a novel class of dynamically bio-responsive polymers, may open new perspectives to overcome this particular barrier by accommodating various secondary structures and form supramolecular structures in such bacterial microenvironments. Generally, bio-responsive polymers are not only candidates as bio-active molecules against bacteria but also carriers via their interactions with the cargo. Singh et al. (2019) [1] Based on their dynamicity, design flexibility, biodegradability, biocompatibility, and pH-responsiveness, we investigated the potential of two peptide-based biodynamers for improving antimicrobial drug delivery. By a range of experimental methods, we discovered a greater affinity of Arg-biodynamers for bacterial membranes than for mammalian membranes as well as an enhanced LPS targeting on the bacterial membrane, opening perspectives for enhancing the delivery of antimicrobials across the Gram-negative bacterial cell envelope. This could be explained by the change of the secondary structure of Arg-biodynamers into a predominant β-sheet character in the LPS microenvironment, by contrast to the α-helical structure typically observed for most lipid membrane-permeabilizing peptides. In comparison to poly-L-arginine, the intrinsic antibacterial activity of Arg-biodynamers was nearly unchanged, but its toxicity against mammalian cells was >128-fold reduced. When used in bacterio as an antibiotic potentiator, however, Arg-biodynamers improved the minimum inhibitory concentration (MIC) against Escherichia coli by 32 times compared to colistin alone. Similar effect has also been observed in two stains of Pseudomonas aeruginosa. Arg-biodynamers may therefore represent an interesting option as an adjuvant for antibiotics against Gram-negative bacteria and to overcome antimicrobial resistance.

Synthesis and characterization of a dithiodiglycolic acid-incorporated poly(glycerol sebacate) exhibiting lipase resistance and antibacterial properties

Poly(glycerol sebacate) (PGS), a crosslinked network synthesized by polycondensation of glycerol and sebacic acid, has found successful utilization in various tissue engineering applications because of its biocompatibility, ease of synthesis, surface-erosion biodegradability, rubber-like elasticity, and adjustable mechanical properties. However, its fast in vivo degradation and lack of intrinsic antibacterial activity may be a concern for specific applications. The functional groups of glycerol and sebacic acid can react with those of other monomers, offering unlimited possibilities for generating new crosslinked networks tailored for particular purposes. Herein, we synthesized a series of poly(glycerol sebacate dithiodiglycolate) (PGSDTG) by incorporation of dithiodiglycolic acid (DTG) in the synthesis of PGS. PGSDTG exhibited the reduced stiffness, sensitive to glutathione (GSH), resistance to lipase degradation, and inhibition of the adhesion and growth of bacteria. The PGSDTG containing 45.6 wt% of DTG exhibited the lowest degradation rate with more than 80 % of PGSDTG weight remained at day 28 and the lowest bacterial inactivation rates of 99.2 ± 0.5 % and 82.5 ± 11.0 % against S. aureus and E. coli. This study suggested that PGSDTG may serve as a suitable antibacterial scaffold material for repairing or regenerating tissues characterized by a slow healing rate.

Surface Modification of Hydroxyapatite Coating for Enhanced Antibiotic Therapy

A major strategy to combat implant-associated infections is to develop implant coatings with intrinsic antibacterial activity. Since hydroxyapatite (HAp) coatings and antibiotic administration are commonly used in clinical settings, developing HAp-coated implants with localized antibiotic-releasing properties has attracted popularity. Considering the antibacterial metal species (Ag, Zn, Cu, etc.) in metal–organic frameworks and their drug delivery capacity, in this study, a gentamicin-loaded zeolitic imidazolate framework-8 nanolayer was deposited on a plasma-sprayed HAp coating (HAp/ZIF-8@Gent), which served as a Gent and Zn2+ reservoir. The investigation on the binding interaction between ZIF-8 and HAp indicated that the growth of ZIF-8 was through a Zn2+ seed layer on the HAp coating via an adsorption–replacement mechanism, instead of simple physical adsorption. The HAp/ZIF-8@Gent coating exhibited a sustained drug-release property, and the cumulative concentration of released Gent reached 239.8 ± 7.1 μg/mL on day 8. Compared to the HAp-Zn and HAp/ZIF-8 coatings, the HAp/ZIF-8@Gent coating exhibited significantly higher antibacterial activity against E. coli. This was ascribed to the combined antibacterial effects of Zn2+ and Gent. The cytocompatibility of the HAp/ZIF-8@Gent coating was confirmed via cell proliferation. Above all, the ZIF-8-modified HAp coating with localized delivery of Gent and Zn2+ possessed excellent antibacterial activity and acceptable cytocompatibility, showing potential in mitigating implant-associated infections.

Investigation of Siderophore-Platinum(IV) Conjugates Reveals Differing Antibacterial Activity and DNA Damage Depending on the Platinum Cargo.

The growing threat of bacterial infections coupled with the dwindling arsenal of effective antibiotics has heightened the urgency for innovative strategies to combat bacterial pathogens, particularly Gram-negative strains, which pose a significant challenge due to their outer membrane permeability barrier. In this study, we repurpose clinically approved anticancer agents as targeted antibacterials. We report two new siderophore-platinum(IV) conjugates, both of which consist of an oxaliplatin-based Pt(IV) prodrug (oxPt(IV)) conjugated to enterobactin (Ent), a triscatecholate siderophore employed by Enterobacteriaceae for iron acquisition. We demonstrate that l/d-Ent-oxPt(IV) (l/d-EOP) are selectively delivered into the Escherichia coli cytoplasm, achieving targeted antibacterial activity, causing filamentous morphology, and leading to enhanced Pt uptake by bacterial cells but reduced Pt uptake by human cells. d-EOP exhibits enhanced potency compared to oxaliplatin and l-EOP, primarily attributed to the intrinsic antibacterial activity of its non-native siderophore moiety. To further elucidate the antibacterial activity of Ent-Pt(IV) conjugates, we probed DNA damage caused by l/d-EOP and the previously reported cisplatin-based conjugates l/d-Ent-Pt(IV) (l/d-EP). A comparative analysis of these four conjugates reveals a correlation between antibacterial activity and the ability to induce DNA damage. This work expands the scope of Pt cargos targeted to the cytoplasm of Gram-negative bacteria via Ent conjugation, provides insight into the cellular consequences of Ent-Pt(IV) conjugates in E. coli, and furthers our understanding of the potential of Pt-based therapeutics for antibacterial applications.

Design of new zwitterionic microparticles with intrinsic antibacterial activity

AbstractThe crosslinked porous microparticles based on glycidyl methacrylate, N‐vinylimidazole, and triethylene glycol dimethacrylate (molar ratio between monomers 40:30:30) obtained in the presence of three porogenic agents (toluene, n‐butyl acetate, and toluene:n‐butyl acetate mixture, 1:1, v/v) are used as precursors in the polymer analogous reactions with some betainizing agents (sodium monochloroacetate, acrylic acid, methacrylic acid and 1,3–propane sultone) in order to introduce the carboxybetaine/sulfobetaine groups to the tertiary nitrogen atom from the imidazole ring. ATR–FTIR spectroscopy is used to highlight the presence of carboxybetaine/sulfobetaine groups on the structure of the microparticles, but also to calculate the degree of betainization (55.91%–90.2%) The zwitterionic microparticles are characterized by scanning electron and atomic force microscopies, equilibrium swelling ratio as a function of pH values, swelling kinetics, ion exchange capacities and particle size distribution. Also, the parameters of porous structure (pore diameter, pore volume, porosity, and specific surface area) are determined by mercury porosimetry. The antibacterial properties of Gram‐positive (Enterococcus faecalis and Staphylococcus aureus) and Gram‐negative (Escherichia coli and Klebsiella pneumoniae) bacteria are evaluated. It is found that the zwitterionic structures containing a shorter length alkyl chain between ionic groups exhibit excellent antibacterial activity of about 80%–92%.

Reimagining Chitosan‐Based Antimicrobial Biomaterials to Mitigate Antibiotic Resistance and Alleviate Antibiotic Overuse: A Review

AbstractThis paper reports recent advancements in chitosan‐based antimicrobial biomaterials that aim to address the issue of antimicrobial resistance (AMR). Today, AMR is one of the most significant public health challenges the world is facing. To combat the overuse of antibiotics, a range of materials, including advanced nanosized polymers, have been explored as potential antimicrobial agents. In this direction, chitosan scores highly because of its unique combination of properties such as biodegradability, biocompatibility, bioactivity, non‐toxic, and, most importantly, its intrinsic antibacterial and antifungal activity. Herein, an overview of chitosan and its derivatives as potential alternatives to conventional antimicrobial therapeutics is reported. This review starts with understanding the AMR mechanism, which is critical for developing suitable materials for treating infectious diseases. Then, the inherent characteristics, modes of antimicrobial action, and factors that impact the antimicrobial effectiveness of chitosan and its derivatives are discussed. The authors further summarize various clinical trial results of chitosan‐based materials as antimicrobial agents. Finally, various antimicrobial applications of chitosan‐based materials are reported. In summary, this review offers new insights into the design of chitosan‐based sustainable materials for various antimicrobial applications.

Oligo(ethylene glycol) methyl ether methacrylate based hydrogel with intrinsic antibacterial activity against Pseudomonas aeruginosa as a model of a major wound infecting human pathogen

Wound dressings represent the first important defense line against potentially life-threatening infections. Successful materials should unify efficiency, simplicity of production with the ease of application. Cationic polymers based on quaternary ammonium salt moieties along the polymer chain promise high efficacy against growth of relevant pathogens including drug-resistant strains. We present a novel and easy-to-handle wound dressing material based on the well-defined copolymers of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), using quaternization with 1,6-dibromohexane for hydrogel formation. The material obtained from this robust approach was perfectly biocompatible with human dermal fibroblasts and revealed an auspicious degree of intrinsic antibacterial activity against P. aeruginosa as a model pathogen for hospital-acquired infections. Formation of bacterial biofilms was prevented in early- and late-stages and even planktonic cells were killed upon gel contact. The rheological properties of the hydrogel materials were comprehensively characterized in both dry and swollen states. Excellent biological performance and appropriate viscoelastic properties qualify the hydrogels from our production approach as truly promising novel wound dressing materials with long-lasting and contact-active bactericidal activities. We believe that this charmingly simple procedure and the mechanical properties of the hydrogel may open new avenues towards cost-effective next-generation first-line wound-care materials.

Fabrication of antimicrobial cationic hydrogels driven by physically and chemically crosslinking for wound healing

The wound therapy based on antibiotic delivery inevitably leads to the emergence of drug resistance. Hydrogel biomaterials with inherent antibacterial activities have emerged as promising candidates for addressing this issue. However, developing an inherently antibacterial hydrogel through simple and facile strategies to promote localized wound infection healing remains a challenge. In this study, we successfully constructed antimicrobial cationic hydrogels with self-healing and injectable properties through physically and chemically dual-crosslinked networks. The networks were formed by the copolymers poly[(di(ethylene glycol) methyl ether methacrylate)-co-(4-formylphenyl methacrylate)-co-(2-(methacryloyloxy)ethyl]trimethylammonium chloride solution)] (PDFM) and poly[(di(ethylene glycol) methyl ether methacrylate)-co-(2-aminoethyl methacrylate hydrochloride)-co-(2-(((6-(6-methyl-4[1H]pyrimidionylureido) hexyl)carbamoyl)oxy)ethyl methacrylate)] (PDAU). The hydrogel systems effectively facilitate the regeneration and healing of infected wounds through the contact bactericidal feature of quaternary ammonium cations. The presence of Schiff base bonds in the injectable hydrogels imparts remarkable pH responsiveness and self-healing properties. In vitro experiments verified their intrinsic antibacterial activities along with their favorable cytocompatibility and hemocompatibility in both in vitro and in vivo. In addition, the hydrogel significantly accelerated the healing of bacterially infected in a full-thickness skin wound. This facilely prepared dual-crosslinked hydrogel, without antibiotics loading, holds significant prospects for treating infected wounds.

Antimicrobial and Antibiofilm Potential of PEGylated Chitosan-Based Nano-Antibiotics Against Multidrug-Resistant E Coli Strains

Antimicrobial and Antibiofilm Potential of PEGylated Chitosan-Based Nano-Antibiotics Against Multidrug-Resistant E Coli Strains

Investigating the Antibacterial Activities of Graphene Oxide Loaded Spiky Gold Nanocomposites via Chitosan linker

The graphene oxide (GO) loaded spiky gold (AuNS) nanocomposites were prepared by electrostatic interaction between negatively-charged GO nanosheets and positively-charged AuNS by the assistance of chitosan as linker molecules. The AuNS/GO nanocomposites exhibit a red-shift in the extinction spectra and a reduction in the zeta potential compared to those of the pristine AuNS due to the presence of oxygen-containing functional groups in GO. The bactericidal analysis demonstrates that the incorporation of GO greatly enhances the intrinsic antibacterial activities of AuNS. Besides, the AuNS with smaller size exhibit better bactericidal efficiency compared to that of AuNS with bigger size. Upon light irradiation, the AuNS/GO with the absorption peak close to the wavelength of excitation light (900 vs. 904 nm) demonstrates a noticeable improvement in the bactericidal efficiency which is attributed to the plasmon-induced photothermal effect. All these results suggest that the AuNS/GO nanocomposites can work as a promising functional material for both intrinsic and plasmon-induced antibacterial materials.

UPLC–QTOF-MS/MS analysis of saponin-enriched fractions from Calliandra umbellifera Benth and evaluation of antibacterial activity against multidrug-resistant bacteria

The genus Calliandra, rich in diterpenes, flavonoids, tannins and saponins, has several species with medicinal use. The species Calliandra umbellifera has abundant saponins in its composition, it is a glycoside that acts in defense against insects and pathogens. Due to these properties, saponins have been described to have antibacterial, antifungal, antiparasitic, anti-inflammatory and antiviral activity. Thus, the present work aimed to isolate the saponin-rich fraction of the Calliandra umbellifera species (FRSCu) and to evaluate the antibacterial activity against standard and multidrug-resistant bacterial species. The fraction was obtained from the preparation of the ethanolic extract of the species, being characterized by chromatography, using the method ultra-efficient liquid chromatography coupled to quadrupole/time of flight system (UPLC–QTOF-MS/MS). Minimum inhibitory concentration (MIC) assays were performed to verify the inhibition of bacterial growth for standard and multiresistant strains of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, as well as the evaluation of the activity when combined with the antibiotics: gentamicin, norfloxacin and ampicillin. The chemical analysis of FRSCu allowed the identification of the presence of phenolic compounds, flavonoids, condensed tannins and saponins. The intrinsic antibacterial activity of FRSCu did not show relevant results against the bacteria used. However, it showed promising results when combined with antibiotics, enhancing the effect of gentamicin against two gram-negative strains E. coli and P. aeruginosa and also when combined with norfloxacin against P. aeruginosa. Thus, this work presents an innovative and biotechnological potential that can contribute to future pharmaceutical formulations and knowledge about the C. umbellifera species.

I n vitro pharmacokinetics/pharmacodynamics of the β-lactamase inhibitor, durlobactam, in combination with sulbactam against Acinetobacter baumannii-calcoaceticus complex.

Infections caused by Acinetobacter baumannii are increasingly multidrug resistant and associated with high rates of morbidity and mortality. Sulbactam is a β-lactamase inhibitor with intrinsic antibacterial activity against A. baumannii. Durlobactam is a non-β-lactam β-lactamase inhibitor with an extended spectrum of activity compared to other inhibitors of its class. In vitro pharmacodynamic infection models were undertaken to establish the pharmacokinetic/pharmacodynamic (PK/PD) index and magnitudes associated with sulbactam and durlobactam efficacy and to simulate epithelial lining fluid (ELF) exposures at clinical doses to understand sulbactam-durlobactam activity with and without co-administration of a carbapenem. Hollow fiber infection models (HFIMs) and one-compartment systems were used to identify the PK/PD indices and exposure magnitudes associated of 1-log10 and 2-log10 colony-forming unit (CFU)/mL reductions. Sulbactam and durlobactam demonstrated PK/PD drivers of % time above the minimum inhibition concentration (%T > MIC) and area under the plasma concentration-time curve from time 0 to 24 h (AUC0-24)/MIC, respectively. Against a sulbactam-susceptible strain, sulbactam %T > MIC of 71.5 and 82.0 were associated with 1-log10 and 2-log10 CFU/mL reductions, respectively, in the HFIM. Against a non-susceptible strain, durlobactam restored the activity of sulbactam with an AUC0-24/MICs of 34.0 and 46.8 using a polysulfone cartridge to achieve a 1-log10 and 2-log10 CFU/mL reduction. These magnitudes were reduced to 13.8 and 24.2, respectively, using a polyvinylidene fluoride cartridge with a membrane pore size of 0.1 μm. In the one-compartment model, durlobactam AUC0-24/MIC to achieve 1-log10 and 2-log10 CFU/mL reduction were 7.6 and 33.4, respectively. Simulations of clinical ELF exposures in the HFIM showed cidal activity at MICs ≤4 µg/mL. Penicillin binding protein 3 mutant strains with MICs of 8 μg/mL may benefit from the addition of a carbapenem at clinical exposures.

In vivo dose response and efficacy of the β-lactamase inhibitor, durlobactam, in combination with sulbactam against the Acinetobacter baumannii-calcoaceticus complex.

Multi-drug resistant (MDR) Acinetobacter baumannii is emerging as a pathogen of increasing prevalence and concern. Infections associated with this Gram-negative pathogen are often associated with increased morbidity and mortality and few therapeutic options. The β-lactamase inhibitor sulbactam used commonly in combination with ampicillin demonstrates intrinsic antibacterial activity against A. baumannii acting as an inhibitor of PBP1 and PBP3, which participate in cell wall biosynthesis. The production of β-lactamases, particularly class D oxacillinases, however, has limited the utility of sulbactam resorting to increased doses and the need for alternate therapies. Durlobactam is a non-β-lactam β-lactamase inhibitor that demonstrates broad β-lactamase inhibition including class D enzymes produced by A. baumannii and has shown potent in vitro activity against MDR A. baumannii, particularly carbapenem-resistant isolates in susceptibility and pharmacodynamic model systems. The objective of this study is to evaluate the exposure-response relationship of sulbactam and durlobactam in combination using in vivo neutropenic thigh and lung models to establish PK/PD exposure magnitudes to project clinically effective doses. Utilizing established PK/PD determinants of %T>MIC and AUC/MIC for sulbactam and durlobactam, respectively, non-linear regressional analysis of drug exposure was evaluated relative to the 24-hour change in bacterial burden (log10 CFU/g). Co-modeling of the data across multiple strains exhibiting a broad range of MIC susceptibility suggested net 1-log10 CFU/g0 reduction can be achieved when sulbactam T>MIC exceeds 50% of the dosing interval and durlobactam AUC/MIC is 10. These data were ultimately used to support sulbactam-durlobactam dose selection for Phase 3 clinical trials.

Antibacterial hyaluronic acid hydrogels with enhanced self-healing properties via multiple dynamic bond crosslinking

The self-healing hydrogel offering intrinsic antibacterial activity is often required for the treatment of wounds because it can provide effective wound protection and prevent wound infection. Herein, antibacterial hyaluronic acid hydrogels with enhanced self-healing performances are prepared by multiple dynamic-bond crosslinking between aldehyde hyaluronic acid, 3, 3′- dithiobis (propionyl hydrazide) and fungal-sourced quaternized chitosan. Due to the formation of these different types of reversible interactions e.g. hydrazone bonds, disulfide bonds, and electrostatic interactions, the hyaluronic acid hydrogels can gel rapidly and exhibit excellent self-healing ability, which can heal completely within 1 h. Furthermore, the hydrogels show good antibacterial activity against E. coli and S. aureus with an inhibition ratio of ~100 % and above 75 %, respectively. Additionally, the hydrogels are cytocompatible, which makes them the potential for biomedical applications e.g. cell culture, tissue engineering, and wound dressing.

Crown ether-based porous organic polymer encapsulated Ag2[Fe(CN)5NO] composite towards ultra-low dose efficient sterilization and wound healing application

The exploration of safe and efficient antibiotic-free antimicrobial agents, harboring the capacities of concurrent antibacterial and wound healing, are highly desired to combat the drug-resistance bacteria. In this report, a nanord-like crown ether-based porous organic polymer (CEP-POP) with intrinsic antibacterial activity containing porphyrin unites, was facilely prepared, which was implemented as a carrier to deposit silver nitroprusside nanoparticles (abbreviated as AgNNPs), denoted as CEP-POP-AgNNP. CEP-POP-AgNNP could effectively address the issues of Ag-based bactericide, which not only significantly enhance the stability of Ag-based bactericide, but also greatly reduce the toxicity to normal tissues. Bacteriostatic study demonstrated CEP-POP-AgNNP could function as a broad-spectrum antibacterial agent with superb synergistic bactericidal activity, whose bactericide rate reached 97.7 ± 0.5 % and 90.7 ± 0.5 %, towards E. coli and S. aureus, respectively, at an extremely low inhibitory concentration (5 μg mL−1), far exceeding the as-reported POP-based antimicrobials. Meanwhile, in vivo experiment on mice validated CEP-POP-AgNNP could further enhance the wound healing in synergy with the antibacterial effect. Hence, this novel but simple Ag immobilization strategy paves a new avenue for the rational design of antibiotic-free antimicrobial agents.

Tunable fluorescent biomass-derived carbon dots for efficient antibacterial action and bioimaging

Carbon dots (CDs)-based antibacterial biomaterials offer great potential in addressing the severe threat of antibiotic-resistant bacteria to public health. Positively charged CDs usually adhere on bacterial membranes via electrostatic interactions, however, they may cause hemolysis and cytotoxicity, and dissatisfactory fluorescence emission restricts their applications in bioimaging. Herein, we developed a negatively charged tunable multicolor nitrogen and phosphorus co-doped CDs (N, P-CDs) from mango peel, a renewable food waste biomass. The N, P-CDs exhibit good biocompatibility and photostability, thus could be adopted to multicolor cell labeling in vitro. More importantly, the negatively charged N, P-CDs possess intrinsic antibacterial activity against E. coli and S. aureus, and antimicrobial mechanisms were investigated by real-time quantitative PCR (RT-qPCR). We found the different mechanisms of N, P-CDs against E. coli and S. aureus, the antibacterial mechanism of N, P-CDs against E. coli mainly involve inhibition of binary fission proliferation and transcription of genetic information, interference with carbon metabolism and sugar conversion, thus inducing growth arrest and cell death. For S. aureus, N, P-CDs could serve as quorum sensing (QS) inhibitor to disrupt QS system, inhibit biofilm formation, DNA replication, cell division, and signal transmission. Our study provides important insights into antibacterial mechanism of CDs at the molecular level, which may facilitate the further exploration and application of natural resources-based antibacterial biomaterials.

Durably and intrinsically antibacterial polyamide 6 (PA6) via backbone end-capping with high temperature-resistant imidazolium

The antibacterial polyamide 6 (PA6) material has attracted great research interest due to its wide application in food packaging, biomedical fields, functional textiles, and other fields. However, it is still a challenge to prepare intrinsically antibacterial PA6 with highly efficient and durably antibacterial activity via polymerization. Herein, the antibacterial imidazolium ionic liquid of 3-carboxymethyl-1-decyl imidazole chloride was designed and synthesized for adapting the polymerization and processing temperature of PA6. Then antibacterial PA6 (PA6-IL) was synthesized through hydrolyzed ring-opening copolymerization with imidazolium at the end of the backbones. Compared to physical blending or post-modification methods, antibacterial agents as end-capping reagents of polymer backbones endowed PA6 with intrinsic antibacterial activity. As expected, the obtained PA6-IL exhibited not just comparable physicochemical and mechanical properties to conventional PA6 but excellent antibacterial activity of low antibacterial time to 60 min and durability for 28 days. Additionally, the corresponding electrospun PA6-IL nanofibrous membranes showed homogenous morphology and remarkable hydrophilicity of 7.7° as well as the high-efficient antibacterial activity. Melt-spun PA6-IL microfibers revealed a smooth surface as well as enhanced tensile strength and increased breaking elongation compared to those of conventional PA6. The PA6-IL microfibers also behaved with excellent antibacterial efficiency and durability. Accordingly, this work provides a feasible and straightforward strategy to prepare durably and intrinsically antibacterial PA6 materials especially PA6 fibers, which can be widely applied in the textiles field.