Evaluation of Novel Antibacterial N-Halamine Nanoparticles Prodrugs towards Susceptibility of Escherichia coli Induced by DksA Protein

Novel N-halamine nanoparticles potentially useful for killing pathogenic bacteria, i.e., SiO2@PS/N-halamine NPs, were successfully synthesized via the immobilization of N-halamines onto the polystyrene-coated silica nanoparticles (SiO2@PS NPs). The effect of reaction conditions, i.e., chlorination temperature, bleaching concentration, chlorination time, on the oxidative chlorine content in the products was systematically investigated. The antibacterial activity of the products was tested via the modified plate counting methd using Escherichia coli (E. coli) as a model bacterium. The possible mechanism of the antibacterial action of the products was also studied using scanning electron microscopy combined with a inhibition zone study. The antimicrobial capability of the products was well controlled by tuning the oxidative chlorine content in the products. More importantly, the role of DksA protein in the susceptibility of E. coli against the products was proven using a time-kill assay. This in-depth investigation of the sensitivity of E. coli towards N-halamine NPs provides a systematic understanding of the utility of N-halamines for deactivating bacteria or even disease control

An N-Halamine/Graphene Oxide-Functionalized Electrospun Polymer Membrane That Inactivates Bacteria on Contact and by Releasing Active Chlorine

The emergence of antibiotic-resistant “superbugs” in recent decades has led to widespread illness and death and is a major ongoing public health issue. Since traditional antimicrobials and antibiotics are in many cases showing limited or no effectiveness in fighting some emerging pathogens, there is an urgent need to develop and explore novel antibacterial agents that are both powerful and reliable. Combining two or more antibiotics or antimicrobials has become a hot topic in antibacterial research. In this contribution, we report on using a simple electrospinning technique to create an N-halamine/graphene oxide-modified polymer membrane with excellent antibacterial activity. With the assistance of advanced techniques, the as-obtained membrane was characterized in terms of its chemical composition, morphology, size, and the presence of active chlorine. Its antibacterial properties were tested with Escherichia coli (E. coli) as the model bacteria, using the colony-counting method. Interestingly, the final N-halamine/graphene oxide-based antibacterial fibrous membrane inactivated E. coli both on contact and by releasing active chlorine. We believe that the synergistic antimicrobial action of our as-fabricated fibrous membrane should have great potential for utilization in water disinfection, air purification, medical and healthcare products, textile products, and other antibacterial-associated fields

Synthesis, Characterization, and Bactericidal Evaluation of Chitosan/Guanidine Functionalized Graphene Oxide Composites

In response to the wide spread of microbial contamination induced by bacterial pathogens, the development of novel materials with excellent antibacterial activity is of great interest. In this study, novel antibacterial chitosan (CS) and polyhexamethylene guanidine hydrochloride (PHGC) dual-polymer-functionalized graphene oxide (GO) (GO-CS-PHGC) composites were designed and easily fabricated. The as-prepared materials were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectrometer (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA) and Raman spectroscopy. Their antibacterial capability towards bacterial strains was also studied by incubating both Gram-negative bacteria and Gram-positive bacteria in their presence. More significantly, the synergistic antibacterial action of the three components was assayed, and the findings implied that the as-prepared GO-CS-PHGC shows enhanced antibacterial activity when compared to its single components (GO, CS, PHGC or CS-PHGC) and the mixture of individual components. Not only Gram-negative bacteria but also Gram-positive bacteria are greatly inhibited by GO-CS-PHGC composites. The minimum inhibitory concentration (MIC) value of GO-CS-PHGC against E. coli was 32 μg/mL. With the powerful antibacterial activity as well as its low cost and facile preparation, GO-CS-PHGC has potential applications as a novel antibacterial agent in a wide range of biomedical uses

Application of Molecularly Imprinted Polymers in Plant Natural Products: Current Progress and Future Perspectives

Abstract Plants, as a large and complex system, are rich in a variety of natural bioactive constituents. It is crucial to enrich, isolate, purify and detect these natural products. Molecularly imprinted polymers (MIPs) are a class of polymers prepared by molecularly imprinted technology (MIT) that have specific recognition sites and are complementary to templates in shape, size, and binding groups. The synthesis and polymerization mechanism of MIPs are introduced. A variety of preparation methods for MIPs have been developed. MIPs can be classified into three types: non‐covalent molecularly imprinted, covalent molecularly imprinted, and semi‐covalent molecularly imprinted. MIPs usually consists of five parts: template, functional monomer, cross‐linker, initiator, and solvent/reagent. With the advantages of high‐specificity binding ability, MIPs have shown excellent efficacy in the separation, enrichment, and purification of plant active products, such as flavonoids, polyphenols, terpenoids, and other components, especially as specific adsorbent materials. Due to the high selectivity to target the analytes, MIPs have also been used as sensors to detect the bioactive constituents in plants. Undeniably, MIPs still face undeniable limitations in the application of plant natural products. The development of MIPs with high selectivity, strong affinity, cost‐effectiveness, sensitivity, and environmental friendliness are valuable and promising

Active iodine regulated in cow dung biochar-based hydrogel combined with PDT/PTT for MRSA infected wound therapy

Iodine has been successed in combating bacteria over a century, but its toxic effects on human skin tissues and cells have been overlooked. In this work, a cow dung biochar-based polyvinyl alcohol/polyvinylpyrrolidone hydrogel (BCPP) was designed to in situ produce iodine on-demand and regulate its release via the light triggering strategy for the infected wound therapy. Benefiting from the reactive oxygen species (ROS) generation and the photothermal conversion properties of cow dung biochar (BC), the as-prepared hydrogel in situ transformed iodide into active iodine under the visible (Vis) light irradiation and regulated the release of active iodine under the near-infrared (NIR) light irradiation. The active iodine combined with photodynamic and photothermal effects of BCPP endowed hydrogel excellent antibacterial effects on ampicillin-resistant Escherichia coli (AREC) and methicillin-resistant Staphylococcus aureus (MRSA) while showing low toxicity to the mammalian cells. The in vivo wound therapy test results demonstrated that this hydrogel resisted MRSA infection, accelerated the healing process, and promoted epithelial regeneration