Novel regenerable N-halamine polymeric biocides. II. Grafting hydantoin-containing monomers onto cotton cellulose

Characterization and Mechanism for the Protection of Photolytic Decomposition of N-Halamine Siloxane Coatings by Titanium Dioxide

N-Halamine antibacterial materials have superior inactivation activities due to oxidative chlorine species. However, N-Cl bonds and bonds between N-halamine and substrates often decompose rapidly under UV irradiation, leading to unrecoverable loss of antimicrobial activity. In this study, titanium dioxide was covalently bonded onto N-halamine siloxane poly[5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin] (PSPH) via a sol-gel process. Experimental testing of the chlorinated cotton fabrics treated with TiO2/PSPH demonstrated that the residual oxidative chlorine in cotton-TiO2/PSPH-Cl was still effective for inactivating bacteria after 50 washing cycles and under UV light irradiation for 24 h. Quantum mechanical calculations found that TiO2 improves the UV stability of the PSPH-Cl system by increasing the activation barrier of the C-Si scission reaction responsible for the loss of the biocidal hydantoin moiety. SEM, XPS and FTIR spectra were used to characterize the coated cotton samples. Cotton-TiO2/PSPH-Cl samples exhibited good antibacterial activity against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895). The storage stability and washing stability of treated cotton fabrics were also investigated.

N-bromo-dimethylhydantoin polystyrene resin for water microbial decontamination

N-bromo-dimethylhydantoin polystyrene beads were synthesized and tested as antimicrobial agents for water microbial decontamination. Optimization of synthetic process was thoroughly investigated, including solvents used, ratio of reactants and reaction conditions, kilogram scale production, and detailed spectral analysis. The microbial inactivation efficiency was studied according to the NSF-231 Guide Standard and Protocol for Testing Microbiological Water Purifiers against Escherichia coli and MS2 phage. The tested resins maintained their activity for 550 L. Thus, N-bromo-dimethylhydantoin-polystyrene beads synthesized under optimized conditions at kilogram quantities have a potential use in water purification filters.

N-Halamine-modified antimicrobial polypropylene nonwoven fabrics for use against airborne bacteria

Disinfecting, nonbleaching compound 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) was uniformly coated onto polypropylene melt-blown nonwoven fabrics having basis-weights of 22 and 50 g/m(2) in order to impart antimicrobial properties via a pad-dry technique. The antimicrobial efficacies of the tested fabrics loaded with MC compound were evaluated against bioaerosols of Staphylococcus aureus and Escherichia coli O157:H7 utilizing a colony counting method. It was determined that both types of coated fabrics exhibited superior antimicrobial efficacy upon exposure to aerosol generation for 3 h. The effect of the coating on air permeability was found to be minimal. Samples were stable for a 6 month time period when they were stored in darkness. However, when the fabrics were exposed to fluorescent light, partial chlorine loss was observed. The MC-coated fabrics exhibited great potential for use in protective face masks and air filters to combat airborne pathogens.

Synthesis and biocidal activity of novel N-halamine hydantoin-containing polystyrenes

Three homopolymers containing hydantoin substituents were obtained by chemical modification of reactive p-chloromethylated polystyrene. The prepared polymers were chlorinated to yield N-halamine materials with biocidal properties. The chemical structure of polymers was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. All of the hydantoin polymers are insoluble in water and common organic solvents. Microbiological investigations prove the high biocidal activity of the obtained chlorinated polystyrene derivatives containing spirohydantoin moieties. The obtained polymers will be useful in designing and constructing medical and pharmaceutical equipment. The ability to crosslink allows to expect easy grafting of these biocidal macrochains, for example, on textiles.

Rapid disinfection by N-halamine polyelectrolytes

Two new N-halamine polyelectrolytes were synthesized, characterized, and deposited onto cotton fabric from a water solution using a layer-by-layer assembly technique. The fabrics were rendered biocidal by a dilute household bleach solution and challenged with Gram-positive and Gram-negative bacteria. The chlorinated swatches (five bilayer coated) inactivated ~106 Staphylococcus aureus and Escherichia coli O157:H7 within only 2 min of contact time. Although the coatings were susceptible to hydrolysis when exposed to repeated washing, the stability of the system was improved by a posttreatment with a cross-linking agent, 3-glycidoxypropyltrimethoxysilane.

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.

Acyclic N-Halamine Polymeric Biocidal Films

Low concentrations of acyclic amide monomers, methacrylamide (MAM) and acrylamide (AM), were copolymerized with vinyl acetate (VAc). No significant differences between the synthesized copolymers and poly(VAc) were seen by 1H-NMR, FTIR, and DSC analysis. Biocidal films, formed by coating the copolymers onto polyester transparency slides and polyester fabric swatches, were chlorinated by exposure to sodium hypochlorite solutions. Both S. aureus and E. coli O157: H7 were completely inactivated within 1 min on the transparency slides and polyester fabric swatches derived from poly(VAc-co-MAM). The chlorine on the films was stable under UVA irradiation and the surfaces were rechargeable upon chlorine loss.

DURABLE AND RECHARGEABLE BIOCIDAL TEXTILES

Textile materials, including natural and synthetic fibers, are good media for growth of microorganisms, particularly the drug-resistant bacteria, which have caused great concern to public health. Biocidal properties should be a necessary feature for medical-use textiles. Biocidal functions, different from biostatic functions, include sterilization, disinfection, and sanitization in an order of the strength. According to guidelines from the US Centers for Disease Control and Prevention (CDC), medical use biocidal functions should be at least at the disinfection level, which can inactivate most infectious microorganisms. In addition, biocidal functions on textile materials should survive repeated laundering if used as uniforms, linens and even reusable surgical scraps and gowns. Among the currently investigated antimicrobial materials, only N-halamines have shown the capability of providing fast and total kill against a wide range of microorganisms without causing resistance from microorganisms. Furthermore, halamine structures can be recharged by chlorine bleaching, a process recommended by CD as well. Thus, biocidal textiles containing the halamine structures have been developed. Recent studies in biocidal polymers have resulted interesting progresses in incorporating halamines to all synthetic fabrics that are widely used as medical and other professional clothing materials. Chemistry and properties of the new processes have been discussed in this presentation.