Preparation and Characterization of Polymerizable Hindered Amine-Based Antimicrobial Fibrous Materials

Fabrication of multifunctional cotton fabrics with quaternized N-halamine endowing the synergetic rechargeable antibacterial, wound healing and self-cleaning performances

Cotton has attracted considerable attention due to its functional characteristics. The focus of research on cotton has shifted in recent years towards designing multi-functional and modified media for cotton fibers, which can be firmly combined with textiles, giving them reusability and extending their service life. This study constructed a synergistic antibacterial layer of quaternary ammonium compounds (QACs) and N-halamine (Hals) using an in-situ free radical copolymerization method in water, named QACs/Hals@cotton-Cl. The route significantly increases the number of antibacterial active centers. FTIR, XPS, and SEM were used to systematically analyze the product's chemical structure, surface morphology, and other characteristics. The modified fabric's antibacterial efficiency, wound healing, renewability, and durability were also evaluated. The chlorinated modified cotton fabric could completely eradicate S. aureus and E. coli within 10 min. Compared with pure cotton, it notably promoted the healing rate of infected wounds in mice. The modification method imparted excellent hydrophobicity to the cotton fabric, with a contact angle exceeding 130°, making it easy to remove surface stains. After 30 days of regular storage and 24 h of UV irradiation, the active chlorine concentration (Cl+%) only decreased by 25 % and 39 %, respectively, and the reduced Cl+% was effectively recharged via simple re-chlorination. The hydrophobicity and antimicrobial properties of QACs/Hals@cotton-Cl remained stable even after 20 cycles of friction. This simple synthesis technique provides a convenient approach for the scalable fabrication of multifunctional and rechargeable antibacterial textiles, with potential applications in medical devices and personal hygiene protection.

Addressing a future pandemic: how can non-biological complex drugs prepare us for antimicrobial resistance threats?

Loss of effective antibiotics through antimicrobial resistance (AMR) is one of the greatest threats to human health. By 2050, the annual death rate resulting from AMR infections is predicted to have climbed from 1.27 million per annum in 2019, up to 10 million per annum. It is therefore imperative to preserve the effectiveness of both existing and future antibiotics, such that they continue to save lives. One way to conserve the use of existing antibiotics and build further contingency against resistant strains is to develop alternatives. Non-biological complex drugs (NBCDs) are an emerging class of therapeutics that show multi-mechanistic antimicrobial activity and hold great promise as next generation antimicrobial agents. We critically outline the focal advancements for each key material class, including antimicrobial polymer materials, carbon nanomaterials, and inorganic nanomaterials, and highlight the potential for the development of antimicrobial resistance against each class. Finally, we outline remaining challenges for their clinical translation, including the need for specific regulatory pathways to be established in order to allow for more efficient clinical approval and adoption of these new technologies.

Crystallization, Mechanical, and Antimicrobial Properties of Diallyl Cyanuric Derivative-Grafted Polypropylene

A functional N-halamine precursor with double bonds, 1-3-diallyl-s-triazine-2,4,6-trione (DTT), was synthesized and grafted onto polypropylene using dicumyl peroxide (DCP) as an initiator via melt blending at 200 °C. The DTT content grafted onto the polypropylene (PP) backbone was depended on both DTT and DCP concentrations in feed. The crystallization temperature of PP increased from 116 °C (neat PP) to 123 °C (10% DTT) with the increasing DTT content. Meanwhile, the crystallization rate and relative crystallinity of PP were significantly increased after introduction of the N-halamine precursor. Moreover, the incorporation of DTT had partial compensation for the decreasing mechanical properties of polypropylene, which resulted from degradation. When the amount of added DTT reached up to 5%, the chlorinated DTT-modified PP sheets were able to kill 105-6 cfu/mL Escherichia coli (CMCC 44103) and Staphylococcus aureus (ATCC 6538) within 10 min. The DTT-modified PP with the regenerating antibacterial property may have great potential for application in packaging, filters, and hygienic products.

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.

Acyclic N-halamine-immobilized polyurethane: Preparation and antimicrobial and biofilm-controlling functions

Hydroxyl groups were introduced onto polyurethane surfaces through 1,6-hexamethylene diisocyanate activation, followed by diethanolamine hydroxylation. Polymethacrylamide was covalently attached to the hydroxylated polyurethane through surface grafting polymerization of methacrylamide using cerium (IV) ammonium nitrate as an initiator. After bleach treatment, the amide groups of the covalently bound polymethacrylamide chains were transformed into N-halamines. The new N-halamine-immobilized polyurethane provided a total sacrifice of 10⁷-10⁸ colony forming units per milliliter of Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), and Candida albicans (fungi) within 10 min and successfully prevented bacterial and fungal biofilm formation. The antimicrobial and biofilm-controlling effects were both durable and rechargeable, pointing to great potentials of the new acyclic N-halamine-immobilized polyurethane for a broad range of related applications.

An N-halamine-based rechargeable antimicrobial and biofilm controlling polyurethane

An N-halamine precursor, 5,5-dimethylhydantoin (DMH), was covalently linked to the surface of polyurethane (PU) with 1,6-hexamethylene diisocyanate (HDI) as the coupling agent. The reaction pathways were investigated using propyl isocyanate (PI) as a model compound. The results suggested that the imide and amide groups of DMH have very similar reactivities toward the isocyanate groups on PU surfaces activated with HDI. After bleach treatment the covalently bound DMH moieties were transformed into N-halamines. The new N-halamine-based PU provided potent antimicrobial effects against Staphylococcus aureus (Gram-positive bacterium), Escherichia coli (Gram-negative bacterium), methicillin-resistant Staphylococcus aureus (MRSA, drug-resistant Gram-positive bacterium), vancomycin-resistant Enterococcus faecium (VRE, drug-resistant Gram-positive bacterium), and Candida albicans (fungus), and successfully prevented bacterial and fungal biofilm formation. The antimicrobial and biofilm controlling effects were stable for longer than 6 months under normal storage in open air. Furthermore, if the functions were lost due to prolonged use they could be recharged by another chlorination treatment. The recharging could be repeated as needed to achieve long-term protection against microbial contamination and biofilm formation.

Sporicidal/bactericidal textiles via the chlorination of silk

Bacterial spores, such as those of the Bacillus genus, are extremely resilient, being able to germinate into metabolically active cells after withstanding harsh environmental conditions or aggressive chemical treatments. The toughness of the bacterial spore in combination with the use of spores, such as those of Bacillus anthracis, as a biological warfare agent necessitates the development of new antimicrobial textiles. In this work, a route to the production of fabrics that kill bacterial spores and cells within minutes of exposure is described. Utilizing this facile process, unmodified silk cloth is reacted with a diluted bleach solution, rinsed with water, and dried. The chlorination of silk was explored under basic (pH 11) and slightly acidic (pH 5) conditions. Chloramine-silk textiles prepared in acidified bleach solutions were found to have superior breaking strength and higher oxidative Cl contents than those prepared under caustic conditions. Silk cloth chlorinated for ≥1 h at pH 5 was determined to induce >99.99996% reduction in the colony forming units of Escherichia coli, as well as Bacillus thuringiensis Al Hakam (B. anthracis simulant) spores and cells within 10 min of contact. The processing conditions presented for silk fabric in this study are highly expeditionary, allowing for the on-site production of protein-based antimicrobial materials from a variety of agriculturally produced feed-stocks.