N-Halamine-Containing Electrospun Fibers Kill Bacteria via a Contact/Release Co-Determined Antibacterial Pathway

Preparation and efficacy of antibacterial methacrylate monomer-based polymethyl methacrylate bone cement containing N-halamine compounds

Introduction

Our objective in this study was to prepare a novel type of polymethyl methacrylate (PMMA) bone cement, analyze its material properties, and evaluate its safety and antibacterial efficacy.

Methods

A halamine compound methacrylate antibacterial PMMA bone cement containing an N-Cl bond structure was formulated, and its material characterization was determined with Fourier transform infrared spectroscopy (FT-IR) and 1H-NMR. The antibacterial properties of the material were studied using contact bacteriostasis and releasing-type bacteriostasis experiments. Finally, in vitro and in vivo biocompatibility experiments were performed to analyze the toxic effects of the material on mice and embryonic osteoblast precursor cells (MC3T3-E1).

Results

Incorporation of the antibacterial methacrylate monomer with the N-halamine compound in the new antibacterial PMMA bone cement significantly increased its contact and releasing-type bacteriostatic performance against Staphylococcus aureus. Notably, at 20% and 25% additions of N-halamine compound, the contact and releasing-type bacteriostasis rates of bone cement samples reached 100% (p < 0.001). Furthermore, the new antibacterial bone cement containing 5%, 10%, and 15% N-halamine compounds showed good biocompatibility in vitro and in vivo.

Conclusion

In this study, we found that the novel antibacterial PMMA bone cement with N-halamine compound methacrylate demonstrated good contact and releasing-type bacteriostatic properties against S. aureus. In particular, bone cement containing a 15% N-halamine monomer exhibited strong antibacterial properties and good in vitro and in vivo biocompatibility.

Physical Contact-Triggered In Situ Reactivation of Antibacterial Hydrogels

In situ reactivation of hydrogels remains a long-standing key challenge in chemistry and materials science. Herein, we first report an ultraconvenient in situ renewable antibacterial hydrogel prepared via a facile physical contact-triggered strategy based on an ultrafast chlorine transfer pathway. We discover that the as-proposed hydrogel with a programmable 3D network cross-linked by noncovalent bonds and physical interactions can serve as a smart platform for selective active chlorine transfer at the hydrogel/hydrogel interface. Systematic experiments and density functional theory prove that the N-halamine glycopolymers integrated into the hydrogel system work as a specific renewable biocide, permitting the final hydrogel to be recharged in situ within 1 min under ambient conditions. Due to its strength and durability, pathogen specificity, and biocompatibility, coupled with its rapid in situ reactivation, this antibacterial hydrogel holds great potential for in vivo biomedical use and circulating water disinfection. We envision this proposed strategy will pave a new avenue for the development of in situ renewable smart hydrogels for real-world applications.

Electrospun Nanofibrous Membranes: A Versatile Medium for Waterproof and Breathable Application

Waterproof and breathable membranes that prevent liquid water penetration, while allowing air and moisture transmission, have attracted significant attention for various applications. Electrospun nanofiber materials with adjustable pore structures, easily tunable wettability, and good pore connectivity, have shown significant potential for constructing waterproof and breathable membranes. Herein, a systematic overview of the recent progress in the design, fabrication, and application of waterproof and breathable nanofibrous membranes is provided. The various strategies for fabricating the membranes mainly including one-step electrospinning and post-treatment of nanofibers are given as a starting point for the discussion. The different design concepts and structural characteristics of each type of waterproof and breathable membrane are comprehensively analyzed. Then, some representative applications of the membranes are highlighted, involving personal protection, desalination, medical dressing, and electronics. Finally, the challenges and future perspectives associated with waterproof and breathable nanofibrous membranes are presented.

Cost-effective fabrication, antibacterial application and cell viability studies of modified nonwoven cotton fabric

In the present work, nonwoven cotton fabric was modified for antibacterial applications using low-cost and eco-friendly precursors. The treatment of fabric with alkali leads to the formation of active sites for surface modification, followed by dip coating with silver nanoparticles and chitosan. The surface was chlorinated in the next step to transform amide (N-H) groups in chitosan into N-halamine (N-Cl). The modified and unmodified surfaces of the nonwoven cotton fabric have been characterized by FTIR, SEM, and XRD. The active chlorine loading is measured with iodine/sodium thiosulphate. The antimicrobial activity and cell toxicity assay were carried out with and without modifications of nonwoven cotton fabric. The antimicrobial efficacies of loaded fabric were evaluated against four bacterial species (Micrococcus luteus, Staphylococcus aureus, Enterobacter aerogenes, and E.coli). It was found that modified fabric exhibited superior efficiency against gram-positive and gram-negative bacterial strains as compared to their bulk counterparts upon exposure without affecting strength and integrity of fabric. The overall process is economical for commercial purposes. The modified fabric can be used for antimicrobial, health, and food packaging industries, and in other biomedical applications.

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.

Application of Electrospinning in Antibacterial Field

In recent years, electrospun nanofibers have attracted extensive attention due to their large specific surface area, high porosity, and controllable shape. Among the many applications of electrospinning, electrospun nanofibers used in fields such as tissue engineering, food packaging, and air purification often require some antibacterial properties. This paper expounds the development potential of electrospinning in the antibacterial field from four aspects: fiber morphology, antibacterial materials, antibacterial mechanism, and application fields. The effects of fiber morphology and antibacterial materials on the antibacterial activity and characteristics are first presented, then followed by a discussion of the antibacterial mechanisms and influencing factors of these materials. Typical application examples of antibacterial nanofibers are presented, which show the good prospects of electrospinning in the antibacterial field.

Long-lasting renewable antibacterial porous polymeric coatings enable titanium biomaterials to prevent and treat peri-implant infection

Peri-implant infection is one of the biggest threats to the success of dental implant. Existing coatings on titanium surfaces exhibit rapid decrease in antibacterial efficacy, which is difficult to promisingly prevent peri-implant infection. Herein, we report an N-halamine polymeric coating on titanium surface that simultaneously has long-lasting renewable antibacterial efficacy with good stability and biocompatibility. Our coating is powerfully biocidal against both main pathogenic bacteria of peri-implant infection and complex bacteria from peri-implantitis patients. More importantly, its antibacterial efficacy can persist for a long term (e.g., 12~16 weeks) in vitro, in animal model, and even in human oral cavity, which generally covers the whole formation process of osseointegrated interface. Furthermore, after consumption, it can regain its antibacterial ability by facile rechlorination, highlighting a valuable concept of renewable antibacterial coating in dental implant. These findings indicate an appealing application prospect for prevention and treatment of peri-implant infection.

Design of nanoengineered antibacterial polymers for biomedical applications

Pathogenic bacteria have become global threats to public health. Since the advent of antibiotics about 100 years ago, their use has been embraced with great enthusiasm because of their effective treatment of bacterial infections. However, the evolution of pathogenic bacteria with resistance to conventional antibiotics has resulted in an urgent need for the development of a new generation of antibiotics. The use of antimicrobial polymers offers the promise of enhancing the efficacy of antimicrobial agents. Of the various antibacterial polymers that effectively eradicate pathogenic bacteria, those that are nanoengineered have garnered significant research interest in their design and biomedical applications. Because of their high surface area and high reactivity, these polymers show greater antibacterial activity than conventional antibacterial agents, by inhibiting the growth or destroying the cell membrane of pathogenic bacteria. This review summarizes several strategies for designing nanoengineered antibacterial polymers, explores the factors that affect their antibacterial properties, and examines key features of their design. It then comments briefly on the future prospects for nanoengineered antibacterial polymers. This review thus provides a feasible guide to developing nanoengineered antibacterial polymers by presenting both broad and in-depth bench research, and it offers suggestions for their potential in biomedical applications.

Recent developments in antimicrobial and antifouling coatings to reduce or prevent contamination and cross-contamination of food contact surfaces by bacteria

Illness as the result of ingesting bacterially contaminated foodstuffs represents a significant annual loss of human quality of life and economic impact globally. Significant research investment has recently been made in developing new materials that can be used to construct food contacting tools and surfaces that might minimize the risk of cross-contamination of bacteria from one food item to another. This is done to mitigate the spread of bacterial contamination and resultant foodborne illness. Internet-based literature search tools such as Web of Science, Google Scholar, and Scopus were utilized to investigate publishing trends within the last 10 years related to the development of antimicrobial and antifouling surfaces with potential use in food processing applications. Technologies investigated were categorized into four major groups: antimicrobial agent-releasing coatings, contact-based antimicrobial coatings, superhydrophobic antifouling coatings, and repulsion-based antifouling coatings. The advantages for each group and technical challenges remaining before wide-scale implementation were compared. A diverse array of emerging antimicrobial and antifouling technologies were identified, designed to suit a wide range of food contact applications. Although each poses distinct and promising advantages, significant further research investment will likely be required to reliably produce effective materials economically and safely enough to equip large-scale operations such as farms, food processing facilities, and kitchens.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.

A comprehensive review on antimicrobial face masks: an emerging weapon in fighting pandemics

The world has witnessed several incidents of epidemics and pandemics since the beginning of human existence. The gruesome effects of microbial threats create considerable repercussions on the healthcare systems. The continually evolving nature of causative viruses due to mutation or re-assortment sometimes makes existing medicines and vaccines inactive. As a rapid response to such outbreaks, much emphasis has been placed on personal protective equipment (PPE), especially face mask, to prevent infectious diseases from airborne pathogens. Wearing face masks in public reduce disease transmission and creates a sense of community solidarity in collectively fighting the pandemic. However, excessive use of single-use polymer-based face masks can pose a significant challenge to the environment and is increasingly evident in the ongoing COVID-19 pandemic. On the contrary, face masks with inherent antimicrobial properties can help in real-time deactivation of microorganisms enabling multiple-use and reduces secondary infections. Given the advantages, several efforts are made incorporating natural and synthetic antimicrobial agents (AMA) to produce face mask with enhanced safety, and the literature about such efforts are summarised. The review also discusses the literature concerning the current and future market potential and environmental impacts of face masks. Among the AMA tested, metal and metal-oxide based materials are more popular and relatively matured technology. However, the repeated use of such a face mask may pose a danger to the user and environment due to leaching/detachment of nanoparticles. So careful consideration is required to select AMA and their incorporation methods to reduce their leaching and environmental impacts. Also, systematic studies are required to establish short-term and long-term benefits.

Highly Antibacterial Efficacy of a Cotton Fabric Treated with Piperazinyl Schiff Base

Due to the structure of hierarchical aligned cellulose fibrils, cotton fabric used in clothing possesses excellent moisture and thermal managements. Such structure yet may retain metabolic excrements and sebum secretions discharged from the human skin, which reproduce microorganisms harmful for human health. However, incorporating the antimicrobial coating into the cotton fabric can sufficiently resist the microorganism growth. In this work, a water-soluble antibacterial coating named N-(4-(allyloxy) benzylidene)-2-(piperazin-1-yl) ethanamine (NABPE) was synthesized to produce a rechargeable and fast sterilization cotton fiber fabric (M-cotton/NABPE). M-cotton/NABPE exhibited a high effective antibacterial activity, and the inhibition ratios against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 94 % and 93 %, respectively. Chlorination was performed with sodium hypochlorite solution to form N-Cl bond on the M-cotton/NABPE fabrics, resulting in a high biocidal efficacy of up to 100 % via contact killing for a duration of 5 min. After 25 washing cycles, the antibacterial fabric still maintained an antibacterial rate of 91.95 % and 92.15 % against E. coli and S. aureus, respectively. Furthermore, the fabrics showed integrated properties of excellent UV stability, long-term stability, robust rechargeable biocidal activity (chlorine recharging >5000 ppm) and washing durability. This research provides fundamental insights into the synthesis of the NABPE and prolonged biocidal efficacy of the M-cotton/NABPE, and thereby pave a pathway to incorporate an economic and environmental-friendly antibacterial coating suitable for finishing cotton fabric.

Antibacterial N-halamine fibrous materials

Pathogenic microbial contamination poses serious threats to human healthcare and economies worldwide, which instigates the booming development of challenging antibacterial materials. N-halamine fibrous materials (NFMs), as an important part of antibacterial materials, featuring structural continuity, good pore connectivity, rapid sterilization, rechargeable bactericidal activity, and safety to humans and environment, have received significant research attention. This review aims to present a systematic discussion of the recent advances in N-halamine antibacterial fibrous materials. We firstly introduce the chemical structures and properties of N-halamine materials. Subsequently, the developed NFMs can be categorized based on their fabrication strategies, including surface modification and one-step spinning. Then some representative applications of these fibrous materials are highlighted. Finally, challenges and future research directions of the materials are discussed in the hope of giving suggestions for the following studies.

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The chemical structures and properties of N-halamine materials are briefly introduced.

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Design and fabrication strategies of N-halamine fibrous materials are systematically reviewed.

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The functional applications of the N-halamine fibrous materials are discussed.

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Challenges and future research directions of the antibacterial N-halamine fibrous materials are provided.

A New Antibacterial N-Halamine Coating Based on Polydopamine

To prevent the formation of biofilms on material surfaces, the latter must have antibacterial properties. The aim of this study is to investigate the synthesis and the antibacterial effect of a new N-halamine coating based on polydopamine (PDA). The benefits of this coating are multiple, notably the green process used to prepare it and the wide variety of organic or inorganic materials that can be functionalized. First, the formation of the PDA coating by oxidative polymerization of dopamine in weak alkaline aqueous solution was studied and characterized. Then, these PDA films were exposed to a NaOCl solution in order to form chloramine functions into the coating, i.e., to immobilize oxidative chlorine on and into the coating. The PDA film chlorination was notably followed in situ by a quartz crystal microbalance (QCM). The influence of the NaOCl solution pH and concentration on chlorination kinetics and on PDA film degradation was evidenced. Finally, the antibacterial properties of the modified PDA coatings were highlighted by testing their antiadhesion and bactericidal properties toward the Escherichia coli bacterial strain.

Contact/Release Coordinated Antibacterial Cotton Fabrics Coated with N-Halamine and Cationic Antibacterial Agent for Durable Bacteria-Killing Application

Coating a cationic antibacterial layer on the surface of cotton fabric is an effective strategy to provide it with excellent antibacterial properties and to protect humans from bacterial cross-infection. However, washing with anionic detergent will inactivate the cationic antibacterial coating. Although this problem can be solved by increasing the amount of cationic antibacterial coating, excessive cationic antibacterial coating reduces the drapability of cotton fabric and affects the comfort of wearing it. In this study, a coordinated antibacterial coating strategy based on quaternary ammonium salt and a halogenated amine compound was designed. The results show that the antibacterial effect of the modified cotton fabric was significantly improved. In addition, after mechanically washing the fabric 50 times in the presence of anionic detergent, the antibacterial effect against Staphylococcus aureus and Escherichia coli was still more than 95%. Furthermore, the softness of the obtained cotton fabric showed little change compared with the untreated cotton fabric. This easy-to-implement and cost-effective approach, combined with the cationic contact and the release effect of antibacterial agents, can endow cotton textiles with durable antibacterial properties and excellent wearability.

Bactericidal and antifouling electrospun PVA nanofibers modified with a quaternary ammonium salt and zwitterionic sulfopropylbetaine

Bacterial adhesion and colonization on material surfaces have attracted great attention due to their potential threat to human health. Combining bactericidal and antifouling functions has been confirmed as an optimal strategy to prevent microbial infection. In this work, biodegradable electrospun polyvinyl alcohol (PVA) nanofibers were chosen due to its high specific area and abundant reactive hydroxyl groups. A quaternary ammonium salt (IQAS) and zwitterionic sulfopropylbetaine (ISB), both containing isocyanate (NCO) groups, were chemically bonded to the PVA nanofiber surface via a coupling reaction between the OH groups of the PVA nanofibers and the NCO groups of IQAS or ISB. The results indicated that the antimicrobial rates of PVA nanofibers modified by IQAS (0.5%) reached 99.9% against both gram-positive Staphylococcus aureus (S. aureus, ATCC 6538) and gram-negative Escherichia coli (E. coli, ATCC 25922). Additionally, the live/dead staining and cytotoxicity test indicated that the dual functional IQAS/ISB/PVA nanofibers exhibited excellent bactericidal and antifouling activities with low cytotoxicity. This work may provide practical guidelines to fabricate bactericidal and antifouling materials for healthcare applications, including but not limited to wound dressings, textile, food packaging and air filtration.

Pyrrolidone-based polymers capable of reversible iodine capture for reuse in antibacterial applications

Numerous emerging and re-emerging advanced materials have been successful in capturing iodine pollutants that pose an unprecedented global challenge to public health. However, little attention has been paid to the reutilization of the captured iodine. Herein, we report on a pyrrolidone-based polymer capable of reversible iodine capture for reutilization in antibacterial applications. The pyrrolidone-based polymer poly(N-vinyl-2-pyrrolidone-co-vinyl acetate), denoted as P(VAc-NVP), was synthesized facilely via a one-step radical copolymerization strategy, and the synthesis was regulated by step-by-step optimization, specifically by tuning the feed ratio of NVP to VAc. The as-synthesized P(VAc-NVP) copolymer functioned as an adsorbent for iodine in various solutions, including water/ethanol, cyclohexane, and petroleum ether, in addition to having the special capability of releasing iodine in the presence of starch or bacteria. This opens up a new horizon for its functional practical use as a flexible adsorbent to capture iodine for safe disposal. Interestingly, the P(VAc-NVP) copolymer, after adsorbing iodine, showed antibacterial ability against pathogenic bacteria, including Staphylococcus aureus and Escherichia coli, when a series of simulated and practical antibacterial assays were conducted. It is believed that this proposed strategy based on the synergism of iodine capture and antibacterial use should have great potential for environmental remediation and public healthcare.

Electrospun nanofibers of polyelectrolyte-surfactant complexes for antibacterial wound dressing application

The development of polyelectrolyte-surfactant complexes (PESCs) has attracted extensive research interest in different fields of applications. However, the liquid state of PESCs has limited their utility in applications where solid materials are required. In this study, novel antibacterial fibers were fabricated via electrospinning PESCs in the solid state without any additives. The PESCs were prepared in aqueous mixtures of pre-hydrolyzed polyacrylonitrile (HPAN), a polyelectrolyte, and cetyltrimethyl ammonium chloride (CTAC), an antibacterial cationic surfactant, by taking advantage of the self-aggregation behavior of the polyelectrolyte and surfactant, which increased the antibacterial agent loading ability and, thus, the antibacterial activity of polymers. By release-killing and contact-killing mechanisms, the as-spun PESC nanofibrous membranes exhibited strong antibacterial ability against both Gram-positive and Gram-negative bacteria, killing 5 log CFU of E. coli and S. aureus within a contact time as short as 30 min. Furthermore, PESCs were blended with polycaprolactone (PCL) to prepare composite nanofibrous membranes as a novel wound dressing, which showed excellent antibacterial activity and favorable cytocompatibility, with the mechanical strength high enough to satisfy the clinical application requirements. The PESC fibers with durable antibacterial activity presented in the current work would be promising for medical applications.

Host defense peptide mimicking poly-β-peptides with fast, potent and broad spectrum antibacterial activities

Microbial infections have always been serious challenges to human health considering that antibiotics almost inevitably induce microbial resistance. Therefore, it is urgent to develop a new antibacterial agent that is active against drug-resistant bacteria and is less susceptible to microbial resistance. In this work, a series of host defense peptide (HDP) mimicking antibacterial poly-β-peptides were synthesized, characterized and evaluated for their biological activities. The best poly-β-peptide within this study (20 : 80 Bu : DM) displays potent and broad spectrum antibacterial activity against antibiotic-resistant super bugs and low toxicity toward mammalian cells. Moreover, these poly-β-peptides are bactericidal and kill bacteria very fast within 5 min. An antimicrobial resistance test demonstrated that bacteria develop no resistance toward the selected poly-β-peptides even over 1000 generations. Our studies demonstrate that random copolymers of heterochiral poly-β-peptides, without the need for defined secondary structures, can mimic the antimicrobial HDP. These results imply the potential application of these poly-β-peptides as new antimicrobial agents to tackle drug resistant antimicrobial infections.

Novel ZnO/N-halamine-Mediated Multifunctional Dressings as Quick Antibacterial Agent for Biomedical Applications

Cutaneous hemorrhage often occurs in daily life which may cause infection and even amputation. This research aims to develop a novel chitosan dressing impregnated with ZnO/N-halamine hybrid nanoparticles for quick antibacterial performance, outstanding hemostatic potential, high porosity, and favorable swelling property through combining sonication and lyophilization processing. After 30 days of storage, about 90% bacterial cell viability loss could be observed toward both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7 within 30 min of contact by colony counting method. The hybrids assembled much more platelet and red blood cell as compared with pure chitosan control. Moreover, the lower blooding clotting index value gave evidence that these composites could control hemorrhaging and reduce the probability of wound infection. No potential skin irritation and toxicity were detected using in vitro cytocompatibility and a skin stimulation test. Therefore, this work demonstrated a facile and cost-effective approach for the preparation of N-halamine-based hybrid sponges which show promising application for wound dressings.

Electrospun Sesbania Gum-Based Polymeric N-Halamines for Antibacterial Applications

Microorganism pollution induced by pathogens has become a serious concern in recent years. In response, research on antibacterial N-halamines has made impressive progress in developing ways to combat this pollution. While synthetic polymer-based N-halamines have been widely developed and in some cases even commercialized, N-halamines based on naturally occurring polymers remain underexplored. In this contribution, we report for the first time on a strategy for developing sesbania gum (SG)-based polymeric N-halamines by a four-step approach Using SG as the initial polymer, we obtained SG-based polymeric N-halamines (abbreviated as cSG-PAN nanofibers) via a step-by-step controllable synthesis process. With the assistance of advanced techniques, the as-synthesized cSG-PAN nanofibers were systematically characterized in terms of their chemical composition and morphology. In a series of antibacterial and cytotoxicity evaluations, the as-obtained cSG-PAN nanofibers displayed good antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as low cytotoxicity towards A549 cells. We believe this study offers a guide for developing naturally occurring polymer-based antibacterial N-halamines that have great potential for antibacterial applications.

Rechargeable polyamide-based N-halamine nanofibrous membranes for renewable, high-efficiency, and antibacterial respirators

Emerging infectious diseases (EIDs) have been acknowledged as a major public health concern worldwide. Unfortunately, most protective respirators used to prevent EID transmission suffer from the disadvantage of lacking antimicrobial activity, leading to an increased risk of cross-contamination and post-infection. Herein, we report a novel and facile strategy to fabricate rechargeable and biocidal air filtration materials by creating advanced N-halamine structures based on electrospun polyamide (PA) nanofibers. Our approach can endow the resultant nanofibrous membranes with powerful biocidal activity (6 log CFU reduction against E. coli), an ultrahigh fine particle capture efficiency of 99.999% (N100 level for masks), and can allow the antibacterial efficacy and air filtration performance to be renewed in a one-step chlorination process, which has never been reported before. More importantly, for the first time, we revealed the synergistic effect involving the intrinsic structure of polymers and the assembling structure of nanofibers on the chlorination capacity. The successful fabrication of such a fascinating membrane can provide new insights into the development of nanofibrous materials in a multifunctional, durable, and renewable form.

Sesbania Gum-Supported Hydrophilic Electrospun Fibers Containing Nanosilver with Superior Antibacterial Activity

In this contribution, we report for the first time on a new strategy for developing sesbania gum-supported hydrophilic fibers containing nanosilver using electrospinning (SG-Ag/PAN electrospun fibers), which gives the fibers superior antibacterial activity. Employing a series of advanced technologies-scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy, and contact angle testing-we characterized the as-synthesized SG-Ag/PAN electrospun fibers in terms of morphology, size, surface state, chemical composition, and hydrophilicity. By adjusting the synthesis conditions, in particular the feed ratio of sesbania gum (SG) and polyacrylonitrile (PAN) to Ag nanoparticles (NPs), we regulated the morphology and size of the as-electrospun fibers. The fibers' antibacterial properties were examined using the colony-counting method with two model bacteria: Escherichia coli (a Gram-negative bacterium) and Staphylococcus aureus (a Gram-positive bacterium). Interestingly, compared to Ag/PAN and SG-PAN electrospun fibers, the final SG-Ag/PAN showed enhanced antibacterial activity towards both of the model bacteria due to the combination of antibacterial Ag NPs and hydrophilic SG, which enabled the fibers to have sufficient contact with the bacteria. We believe this strategy has great potential for applications in antibacterial-related fields.

Reactions of phenolic compounds with monomeric N-halamines and mesoporous material-supported N-halamines

The reactions of a monomeric N-halamine, 1-chloro-5,5-dimethylhydantoin (MCDMH), and a mesoporous material-supported N-halamine (MMSNs) with phenol and p-cresol (two common contaminants in water) were investigated. MCDMH reacted rapidly with the phenolic compounds, and pH values had little effects on the reactions. On the contrary, MMSNs reacted with phenol and p-cresol only when the pH values were higher than 10. Phenol showed a lower reaction rate than p-cresol toward MMSNs. GCMS analysis suggested that MMSNs might react with the phenolic compounds through step-wise electrophilic chlorination reactions, and the main product was 2,4,6-trichlorophenol. The reaction kinetics were studied by following the disappearance of phenolic UV absorption bands, and the kinetic parameters were determined.

Povidone-iodine-functionalized fluorinated copolymers with dual-functional antibacterial and antifouling activities

Povidone-iodine-functionalized fluorinated polymer coatings with dual-functional antibacterial and antifouling activities should be very promising in practical biomedical applications.

Development of new hydantoin-based biocidal polymers with improved rechargeability and anti-microbial activity

Novel hydantoin based co-polymers containing both amide and imide positions for halogen capture with improved rechargeability and antibacterial activity were developed.

N-halamine-based multilayers on titanium substrates for antibacterial application

Bacterial infection is one of the most severe postoperative complications leading to clinical orthopedic implants failure. To improve the antibacterial property of titanium (Ti) substrates, a bioactive coating composed of chitosan-1-(hydroxymethyl)- 5,5-dimethylhydantoin (Chi-HDH-Cl) and gelatin (Gel) was fabricated via layer-by-layer (LBL) assembly technique. The results of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (¹HNMR) and X-ray photoelectron spectroscopy (XPS) showed that Chi-HHD-Cl conjugate was successfully synthesized. Scanning electron microscopy (SEM), atomic force microscope (AFM) and water contact angle measurements were employed to monitor the morphology, roughness changes and surface wettability of Ti substrates, which proved the multilayers coating formation. Antibacterial assay against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) revealed that the Gel/Chi-HDH-Cl modified Ti substrates most efficiently inhibited the adhesion and growth of bacteria. Meanwhile, in vitro cellular tests confirmed that Gel/Chi-HDH-Cl multilayers had no obvious cytotoxicity to osteoblasts. The study thus provides a promising method to fabricate antibacterial Ti-based substrates for potential orthopedic application.

Electrofabrication of functional materials: Chloramine-based antimicrobial film for infectious wound treatment

Electrical signals can be imposed with exquisite spatiotemporal control and provide exciting opportunities to create structure and confer function. Here, we report the use of electrical signals to program the fabrication of a chloramine wound dressing with high antimicrobial activity. This method involves two electrofabrication steps: (i) a cathodic electrodeposition of an aminopolysaccharide chitosan triggered by a localized region of high pH; and (ii) an anodic chlorination of the deposited film in the presence of chloride. This electrofabrication process is completed within several minutes and the chlorinated chitosan can be peeled from the electrode to yield a free-standing film. The presence of active NCl species in this electrofabricated film was confirmed with chlorination occurring first on the amine groups and then on the amide groups when large anodic charges were used. Electrofabrication is quantitatively controllable as the cathodic input controls film growth during deposition and the anodic input controls film chlorination. In vitro studies demonstrate that the chlorinated chitosan film has antimicrobial activities that depend on the chlorination degree. In vivo studies with a MRSA infected wound healing model indicate that the chlorinated chitosan film inhibited bacterial growth, induced less inflammation, developed reorganized epithelial and dermis structures, and thus promoted wound healing compared to a bare wound or wound treated with unmodified chitosan. These results demonstrate the fabrication of advanced functional materials (i.e., antimicrobial wound dressings) using controllable electrical signals to both organize structure through non-covalent interactions (i.e., induce chitosan's reversible self-assembly) and to initiate function-conferring covalent modifications (i.e., generate chloramine bonds). Potentially, electrofabrication may provide a simple, low cost and sustainable alternative for materials fabrication.

STATEMENT OF SIGNIFICANCE

We believe this work is novel because this is the first report (to our knowledge) that electronic signals enable the fabrication of advanced antimicrobial dressings with controlled structure and biological performance. We believe this work is significant because electrofabrication enables rapid, controllable and sustainable materials construction with reduced adverse environmental impacts while generating high performance materials for healthcare applications. More specifically, we report an electrofbrication of antimicrobial film that can promote wound healing.

Synthesis and polymerization of a new hydantoin monomer with three halogen binding sites for developing highly antibacterial surfaces

Novel three halogen capturing hydantoin monomer-based copolymers were synthesized and evaluated for their antibacterial properties.

Povidone-Iodine-Based Polymeric Nanoparticles for Antibacterial Applications

As microbial contamination is becoming more and more serious, antibacterial agents play an important role in preventing and removing bacterial pathogens from microbial pollution in our daily life. To solve the issues with water solubility and antibacterial stability of PVP-I₂ (povidone-iodine) as a strong antibacterial agent, we successfully obtain hydrophobic povidone-iodine nanoparticles (povidone-iodine NPs) by a two-step method related to the advantage of nanotechnology. First, the synthesis of poly(N-vinyl-2-pyrrolidone-co-methyl methacrylate) nanoparticles, i.e., P(NVP-MMA) NPs, was controlled by tuning a feed ratio of NVP to MMA. Then, the products P(NVP-MMA) NPs were allowed to undergo a complexation reaction with iodine, resulting in the formation of a water-insoluble antibacterial material, povidone-iodine NPs. It is found that the feed ratio of NVP to MMA has an active effect on morphology, chemical composition, molecular weight, and hydrophilic-hydrophobic properties of the P(NVP-MMA) copolymer after some technologies, such as SEM, DLS, elemental analysis, ¹H NMR, GPC, and the contact angle test, were used in the characterizations. The antibacterial property of povidone-iodine NPs was investigated by using Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) as model bacteria with the colony count method. Interestingly, three products, such as glue, ink, and dye, after the incorporation of povidone-iodine NPs, show significant antibacterial properties. It is believed that, with the advantage of nanoscale morphology, the final povidone-iodine NPs should have great potential for utilization in various fields where antifouling and antibacterial properties are highly required.