Biocidal Polystyrenehydantoin Beads. 2. Control of Chlorine Loading

Antibacterial Mesoporous Silica Granules Containing a Stable N-Halamine Moiety

High-efficacy and regenerable antimicrobial silica granules were prepared via oxa-Michael addition between poly(vinyl alcohol) (PVA) and methylene-bis-acrylamide (MBA) under the catalysis of sodium carbonate in an aqueous solution. Diluted water glass was added, and the solution pH was adjusted to about 7 to precipitate PVA-MBA modified mesoporous silica (PVA-MBA@SiO₂) granules. N-Halamine-grafted silica (PVA-MBA-Cl@SiO₂) granules were achieved by adding diluted sodium hypochlorite solution. It was found that a BET surface area of about 380 m² g^-1 for PVA-MBA@SiO₂ granules and a Cl⁺% of about 3.80% for PVA-MBA-Cl@SiO₂ granules could be achieved under optimized preparation conditions. Antimicrobial tests showed that the as-prepared antimicrobial silica granules were capable of about a 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 10 min of contact. Furthermore, the as-prepared antimicrobial silica granules can be recycled many times due to the excellent regenerability of their N-halamine functional groups and can be saved for a long time. With the above-mentioned advantages, the granules have potential applications in water disinfection.

Transparent and ultra-tough PVA/alkaline lignin films with UV shielding and antibacterial functions

Lignin and its derivatives can be used to make membranes with natural polymer materials for its properties including ultraviolet adsorption, biodegradable, antibacterial, and antioxidant. However, the lignin film has poor transparency due to the dark color, and how to control the proportion of each component to enhance properties is the main research topic. In this study, a polyvinyl alcohol /alkaline lignin (PVA/AL) composite film with excellent UV-shielding and visible-transparent performance successfully prepared by solution casting. By mixing with the N-halamine precursor 3-(2,3-dihydroxypropyl)-5,5-dimethylhydantoin (DPDMH), the composite film after chlorination showed superb antibacterial efficacy and could inactivate 6.85 log Escherichia coli (E. coli) and 6.57 log Staphylococcus aureus (S. aureus) respectively within 5 min of contact. Moreover, the composite film with 5 wt% AL exhibited ultra-high elongation of 449 % and toughness of 92 MJ/m³, and the toughness and malleability was greatly improved. In addition, with the introduction of AL, the composite film could shield 100 % of the UVB (320-275 nm) and UVC (275-200 nm) spectra and most of the UVA (400-320 nm) spectrum. The films prepared in this work are expected to find applications in promising fields such as in packaging materials and ultraviolet shielding.

Porous antimicrobial starch particles containing N-halamine functional groups

The porous antimicrobial starch particles containing N-Halamine functional groups (PST-MBA-Cl particles) were synthesized by a crosslinking polymerization between starch (ST) and N, N'-methylenebisacrylamide (MBA), and then a chlorination of amide groups of MBA. The synthetic process used only water as the solvent and was environmentally friendly. The results showed that under the optimal preparation conditions, the as-synthesized PST-MBA-Cl particles could have a Cl⁺% of 8.60 %. Antimicrobial tests showed that PST-MBA-Cl particles had very powerful antimicrobial efficacy against both Staphylococcus aureus and Escherichia coli and could completely kill Staphylococcus aureus with a concentration of 2.1 × 10⁶ CFU/mL and Escherichia coli with a concentration of 5.6 × 10⁶ CFU/mL within a contact time of one minute. Furthermore, the N-Halamine functional groups of PST-MBA-Cl particles also showed excellent stability under storage and reproducibility. Therefore, the as-synthesized PST-MBA-Cl particles will have potential applications in water disinfection.

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.

Tailored synthesis of polymer-brush-grafted mesoporous silicas with N-halamine and quaternary ammonium groups for antimicrobial applications

Antimicrobial mesoporous materials with polymer brushes on the surface were prepared, and their structure and antimicrobial performance investigated. Poly ((3-acrylamidopropyl) trimethylammonium chloride) (PAPTMAC) modified mesoporous silica was prepared by a polymer-brush-grafted method through treatment with the initiator 4,4'-azobis (4-cyanovaleric acid) (ACVA) and polymerized with (3-acrylamidopropyl) trimethylammonium chloride (APTMAC). A covalent bond was formed between mesoporous silica and N-halamine precursor; N-H bonds were successfully transformed to N-Cl bonds after chlorination. Morphology and structure of mesoporous silica were affected to some extent after modification. The surface area of the polymerized sample decreased, but was sufficient for further applications. Compare to the original sample, antimicrobial properties of the polymerized samples with quaternary ammonium groups (QAS) increased slightly. After exposure to dilute household bleach, the chlorinated samples showed excellent antimicrobial properties against 100% of S. aureus (ATCC 6538) (7.63 log) and E. coli O157:H7 (ATCC 43895) (7.52 log) within 10 min. The prepared mesoporous silicas with effective antimicrobial properties could be very useful for potential application in water filtration.

Risk reduction assessment of waterborne Salmonella and Vibrio by a chlorine contact disinfectant point-of-use device

Unsafe drinking water continues to burden developing countries despite improvements in clean water delivery and sanitation, in response to Millennium Development Goal 7. Salmonella serotype Typhi and Vibrio cholerae bacteria can contaminate drinking water, causing waterborne typhoid fever and cholera, respectively. Household water treatment (HWT) systems are widely promoted to consumers in developing countries but it is difficult to establish their benefits to the population for specific disease reduction. This research uses a laboratory assessment of halogenated chlorine beads treating contaminated water to inform a quantitative microbial risk assessment (QMRA) of S. Typhi and V. cholerae disease in a developing country community of 1000 people. Laboratory challenges using seeded well water resulted in log10 reductions of 5.44 (± 0.98 standard error (SE)) and 6.07 (± 0.09 SE) for Salmonella serotype Typhimurium and V. cholerae, respectively. In well water with 10% sewage and seeded bacteria, the log10 reductions were 6.06 (± 0.62 SE) and 7.78 (± 0.11 SE) for S. Typhimurium and V. cholerae, respectively. When one infected individual was contributing to the water contamination through fecal material leaking into the water source, the risk of disease associated with drinking untreated water was high according to a Monte Carlo analysis: a median of 0.20 (interquartile range [IQR] 0.017-0.54) for typhoid fever and a median of 0.11 (IQR 0.039-0.20) for cholera. If water was treated, risk greatly decreased, to a median of 4.1 × 10(-7) (IQR 1.6 × 10(-8) to 1.1 × 10(-5)) for typhoid fever and a median of 3.5 × 10(-9) (IQR 8.0 × 10(-10) to 1.3 × 10(-8)) for cholera. Insights on risk management policies and strategies for public health workers were gained using a simple QMRA scenario informed by laboratory assessment of HWT.

Surface functional polymers by post-polymerization modification using diarylcarbenes: introduction, release and regeneration of hydrogen peroxide and bactericidal activity

Functionalized diarylcarbenes are excellent reactive intermediates suitable for the direct surface modification of organic polymers, and these may be used to introduce urea and thiourea functions onto polystyrene at loading levels of up to 2.3 x 10(13) molecules/cm(2). These functions are capable of the reversible binding and release of peroxide at loading levels of up to 0.6 mmol/g and give polymers that display biocidal activity against a spectrum of gram-positive and gram-negative bacteria.

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.

Rechargeable antimicrobial surface modification of polyethylene

Polyethylene films were surface modified, to incorporate amine and amide functionalities, and subsequently were evaluated for their ability to recharge the antimicrobial N-halamine structures after contact with sodium hypochlorite, a common food-approved sanitizer. Surfaces were tested for chlorine retention and release, as well as antimicrobial activity against microorganisms relevant to food quality and food safety, including Escherichia coli K-12, Pseudomonas fluorescens, Bacillus cereus, and Listeria monocytogenes. N-Halamine functionalized polyethylene exhibited chlorine rechargeability, maintaining 5 to 7 nmol/cm2 N-halamine structures for six successive charges. The N-halamine functionalized films achieved a 4-log reduction for all organisms tested and maintained a greater than 3-log reduction for four successive uses, suggesting that the modified polyethylene films are capable of providing rechargeable antimicrobial activity. The modified films exhibited antimicrobial activity in aqueous suspensions (P < 0.05) and reduced microbial growth in diluted broth (P < 0.05), suggesting the potential for biocidal action even in the presence of organic matter. Such a rechargeable antimicrobial surface could supplement existing cleaning and sanitation programs in food processing environments to reduce the adhesion, growth, and subsequent cross-contamination of food pathogens, as well as food spoilage organisms.

N-halamine biocidal coatings

Novel N-halamine siloxane and epoxide coatings are described. The coatings can be rendered biocidal by exposure to dilute bleach. Once the bound chlorine is lost from the coatings, it can be regenerated by further exposure to dilute bleach. Synthetic schemes and biocidal efficacy data are presented. The stabilities of the bound chlorine on the surfaces are also addressed. Substrates employed include sand, textiles, and paint. Potential uses for the technology are discussed.

N-halamine/quat siloxane copolymers for use in biocidal coatings

A series of copolymers incorporating N-halamine siloxane and quaternary ammonium salt siloxane units has been prepared. The primary function of the quat units was to render the siloxane copolymers soluble in water. The copolymers have been coated onto cotton swatches and evaluated for biocidal efficacy against Staphylococcus aureus and Escherichia coli O157:H7. It was determined that both N-halamine and quat functional groups were effective against S. aureus, but only the N-halamine units were effective against Escherichia coli O157:H7. The copolymers should be useful for applications for which aqueous media is preferred over organic solvents to be used during coating procedures.