T. S. Huang

N-halamine biocidal coatings via a layer-by-layer assembly technique.

Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.

Polymeric antimicrobial N-halamine epoxides.

A new N-halamine copolymer has been prepared, characterized, and evaluated for antimicrobial efficacy, stability toward hydrolyses, and stability toward UVA degradation when covalently bound to cellulose fibers. A copolymer of 3-chloro-2-hydroxypropylmethacrylate and glycidyl methacrylate was coated onto cotton, and, after curing, was treated with an aqueous solution containing the potassium salt of 5,5-dimethylhydantoin to form a coating which became antimicrobial upon exposure to househod bleach (sodium hypochlorite). The coating inactivated S. aureus and E. coli O157:H7 within minutes of contact time and was quite stable toward washing and UVA photodegradation.

Antimicrobial N-halamine modified chitosan films

The inherent antimicrobial properties and biodegradability of chitosan make it an ideal candidate for antimicrobial materials. In this study, N-halamine precursor 3-glycidyl-5,5-dimethylhydantoin (GH) was synthesized and bonded onto chitosan by a ring opening reaction between chitosan and GH. The chitosan film modified with the N-halamine precursor could be rendered biocidal after exposure to a dilute household bleach solution. Syntheses routes, characterization data, and antimicrobial test results are presented. The chlorinated films with 2.60 × 10(18) atoms/cm(2) of active chlorine were challenged with Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) and showed good efficacy against these two bacterial species with log reductions of 7.4 and 7.5 within 10 and 5 min of contact time, respectively. These films may serve as potential materials for food packaging and biomedical applications.

N-halamine copolymers for use in antimicrobial paints.

A series of copolymers containing units of a novel hydantoinylacrylamide and the sodium salt of 2-(acrylamido)-2-methylpropanesulfonic acid have been synthesized. The homopolymer of the hydantoinylacrylamide compound was insoluble in water, while the copolymers with the sulfonic acid sodium salt were water-dispersible/soluble, with the solution becoming completely transparent when the feed ratio for the copolymer contained 7 parts of the hydantoin moiety to 3 parts of the sodium sulfonate moiety. The polymers were added into a commercial water-based latex paint, and upon drying, the painted surfaces treated with the water-miscible copolymers were rendered antimicrobial following chlorination with dilute household bleach. The chlorinated homopolymer failed to provide an antimicrobial property for the paint because of its tendency to isolate into aggregates in the paint, while the completely miscible copolymers were capable of 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 5 min of contact time.

Antimicrobial Fibers Created via Polycarboxylic Acid Durable Press Finishing

An N-halamine precursor, m-aminophenyl hydantoin (m-APH), which was rendered antimicrobial through exposure to chlorine bleach, was synthesized and was applied on cotton fabric using polycarboxylic acids as crosslinking agents. Particularly, 1,2,3,4-butanetetracarboxylic acid (BTCA) with m-APH treated cotton fabric resulted in the highest increased wrinkle recovery angle and chlorine content simultaneously. Durability and rechargeability were measured through an AATCC test method and antimicrobial efficacy of BTCA/m-APH treated cotton fabric against Gram-positive and Gram-negative bacteria showed a 6 log reduction within 1 min of contact time.

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.

Improved UV stability of antibacterial coatings with N-halamine/TiO 2

The outstanding advantages of N-halamine materials over other antimicrobial materials are their durable and rechargeable antimicrobial properties, as well as their efficacies in inactivating a broad spectrum of pathogens. Theoretically, the oxidative chlorine of antimicrobial cotton coated with N-halamine hydantoin diol can be restored upon loss of its biocidal efficacy after exposure to ultraviolet light. In this work nano-titania particles were added into the coating solutions containing N-halamine diol and 1,2,3,4-butanetetracarboxylic acid (BTCA), and the coatings were applied to produce antimicrobial cellulose with improved UV stability. The treated cotton fabrics were characterized by FT-IR, SEM, XRD, and XPS. The effects of the coatings on tensile strength and wrinkle recovery angle were investigated. Biocidal efficacies of fabrics coated with hydantoin diol and diol/TiO2 against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) were determined using a modified AATCC 100-1999 method and showed excellent antimicrobial properties against these two bacterial species within a brief contact times. It was found that the addition of Nano-TiO2 in the antimicrobial coatings, especially rutile titanium dioxide, could improve the UV light stability of the chlorinated fabrics coated with hydantoin diol significantly. The UV light stability of N-halamine coatings were enhanced with increasing amounts of rutile TiO2.

N-halamine-bonded cotton fabric with antimicrobial and easy-care properties

N-halamine precursor 2,2,6,6-tetramethyl piperidinol (TMP), a hindered amine light stabilizer, was bonded onto cotton fabric by using 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent. A variety of treating conditions including TMP concentration, curing temperature and time, and catalyst were studied. The treated fabrics were characterized using FTIR spectra and scanning electron microscope (SEM). The cotton fabric treated with TMP precursor could be rendered biocidal upon exposure to dilute household bleach. The chlorinated cotton swatches showed great efficacy and inactivated 100 % of Staphylococcus aureus with 7.1 log reduction with 5 min of contact and 83.25 % of E. coli O157:H7 at 10 min of contact. In addition, the wrinkle recovery angle of the treated cotton fabrics increased from 229 ° of untreated cotton fabrics to 253 °. This study provided a practical finishing process to produce cotton fabrics with easy care and antibacterial functionalities at the same time.

Preparation and characterization of electrospun antimicrobial fibrous membranes based on polyhydroxybutyrate (PHB)

Poly [5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin] (PSPH), an N-halamine precursor was synthesized and employed to prepare antimicrobial biodegradable polyhydroxybutyrate (PHB) fibrous membranes by using an electrospinning technique. After exposure to chlorine bleach, the fibrous membranes could be rendered biocidal. The membranes were characterized by scanning electron microscopy (SEM), fourier transform infrared spectrometry (FT-IR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The tensile strength, wetting property, UV light stability, and controlled release behavior were investigated. Biocidal efficacies of the chlorinated fibrous membranes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7 were evaluated by a modified AATCC Test Method 100-2004. The results showed that the prepared chlorinated membranes have excellent antimicrobial functions which could inactivate 92.10 % S. aureus and 85.04 % E. coli O157: H7 within 30 min of contact time, respectively. From this study, polyhydroxybutyrate (PHB)-based antimicrobial fibrous membranes may further expand the potential use as ecofriendly materials in a variety of applications such as food packaging and biomedical areas.

Antimicrobial Acrylic Fiber

Fibers have been produced from a blend of poly(acrylonitrile) and poly(styrene hydantoin). The fibers were extruded from a single solvent, dimethyl acetamide. The fiber properties from the blended polymers were somewhat poorer than those from the unmodified acrylic fiber, but were still acceptable. The fibers from the polymer blend could be chlorinated to produce halamines and thus rendered antimicrobial. Antimicrobial test results showed efficacy against S. aureus. The ability to regenerate the halamines (and the antimicrobial functionality) lasted through 50 home laundry washings. The chlorine absorption was shown to be proportional to the specific surface area (m2/g) of the fibers, as might be expected for hydrophobic materials which can react with aqueous reagents only on the fiber surface. Although the fibers produced here were rather larger than those typically used in clothing, the data suggest that a typical diameter fiber of the composition produced here would have a specific surface area to allow chlorine absorption approaching 0.5 %. This level of retained chlorine would certainly produce a highly satisfactory antimicrobial effect - substantially better than the experimental data shown herein.