Cationic polymeric N-halamines bind onto biofilms and inactivate adherent bacteria

A Comparative Study of Structural Contribution to Biocidability via Immobilization of Fluorinated and Nonfluorinated Quaternary Ammonium Salts on Top Surfaces

Higher biocidability of fluorinated quaternary ammonium salt (QAS) is usually contributed to its preferential segregation to the surface to better contact with and kill bacteria. However, whether its structure also elicits better performance is still unclear. Herein, the same amount of a fluorinated QAS and its nonfluorinated counterpart are both immobilized on the top surface to eliminate the effect of concentration distribution to only study their structure-biocidability relationship. Briefly, the fluorinated and nonfluorinated QASs were synthesized by quaternization of N,N-dimethylethanolamine with 2-(perfluorooctyl)ethyl bromide that was prepared by bromination of 2-(perfluorooctyl)ethanol and 1-bromodecane, respectively. Polystyrene (PS) and diblock copolymer poly(styrene)-b-poly(tert-butyl acrylate) (PS-PtBA) were successively spin coated on SiO2 wafers at different concentrations to form bilayer structures that have a PS base layer and a PtBA top layer. The tert-butyl acrylate groups of the PtBA layer of 0.9 nm were converted to carboxylic acid groups with trifluoroacetic acid for respective esterification with the two hydroxy-containing QASs. It was observed that the fluorinated and nonfluorinated surfaces fabricated at the maximum comparable esterification yield of 63.5% fully eradicated ∼104 CFU of Staphylococcus aureus and Escherichia coli in 120 and 150 min, respectively, indicating that the fluorocarbon chain is more biocidal through better interpenetration into bacterial membranes. Immobilization of a functionality on top surface provides a universal strategy to study its structural contribution to activity without interference of the concentration distribution.

Novel quat/di-N-halamines silane unit with enhanced synergism polymerized on cellulose for development of superior biocidability

A silane unit with enhanced synergism that is realized using one cationic quaternary ammonium salt (QAS) to draw anionic bacteria to two N-halamine functionalities was designed and polymerized on cellulose for superior biocidability. A monomer containing one tertiary amine, one amide N-H, and one imide N-H, was synthesized via alcoholysis of 3-triethoxysilylpropyl succinic anhydride with 2-(dimethylamino)ethan-1-ol and following esterification with 5-(4-hydroxyphenyl)hydantoin. The triethoxysilyl groups of the monomer were hydrolyzed to silanol groups to condense with counterparts in different hydrolyzates and with hydroxyl groups on cellulose to form a polymeric modifier. Each silane unit of the modifier has one QAS and two N-halamine functionalities (quat/di-N-halamines) after quaternization of the tertiary amine and chlorination of the amide and imide hydrogens. The resultant cellulose suppressed (7 logs) both Staphylococcus aureus and Escherichia coli within 3 min, demonstrating an enhanced synergism since the inactivation rate is faster than counterparts decorated with only N-halamine and with synergistic units of one cationic center and one N-halamine. The modifier exhibited promising stability and rechargeability toward washings, UV irradiation, and long-term storage. The proved enhanced synergism from the integration of one cationic center with multiple N-halamines directs the synthesis of more powerful biocides for developing antibacterial polymers.

Novel composite unit with one pyridinium and three N-halamine structures for enhanced synergism and superior biocidability on magnetic nanoparticles

A novel composite unit of enhanced synergism that rises from the use of a cationic pyridinium structure to attract anionic bacteria to three N-halamine structures was designed for superior biocidability on recyclable magnetic nanoparticles. Briefly, 5-(4-hydroxybenzylidene)hydantoin (HBH), containing one imide and amide NH bonds, was synthesized by Knoevenagel condensation ofp-hydroxybenzaldehyde with hydantoin. 3-Triethoxysilylpropyl succinic anhydride was ammonolyzed with 4-aminopyridine to introduce a pyridine structure and form an amide NH and a carboxylic acid group that was esterified with HBH to introduce its two NH bonds. The triethoxysilyl groups of the esterification product were hydrolyzed into silanols to condense with the counterparts of different hydrolysates and on silica modified Fe₃O₄nanoparticles to provide a layer of polymeric modifier. After quaternization of the pyridine and chlorination of NH bonds from each esterification product, the resultant layer is composed of units each of which contains one pyridinium and threeN-halamine sites and exerted higher biocidability against Escherichia coli and Staphylococcus aureus than comparable systems including synergistic ones with one cationic center and one N-halamine, demonstrating an enhanced synergism. The biocidal layer had promising stability under quenching-chlorinating cycles and long-term storage. The study affords a strategy for syntheses of more powerful biocidal surfaces.

Engineering of antibacterial/recyclable difunctional nanoparticles via synergism of quaternary ammonia salt site and N-halamine sites on magnetic surface

A biocidal composite unit with improved synergism, using one cationic quaternary ammonia salt (QAS) site to attract electronegative bacteria to three highly biocidal N-halamine sites, was designed for the first time and attached onto surface of magnetic silica coated Fe₃O₄ nanoparticles (silica@Fe₃O₄NPs) for superior biocidability, large killing area, and easy recyclability. Briefly, a compound containing one imide and two amide NH bonds, 2-(2,5-dioxoimidazolidin-4-yl)-N-(4-hydroxyphenyl)acetamide (DHPA), was prepared by amidation of hydantoin acetic acid with p-aminophenol. A biocidal precursor of one QAS site and three N-halamine sites was then constructed by alcoholysis of 3-triethoxysilylpropyl succinic anhydride with 2-(dimethylamino)ethan-1-ol to introduce a tertiary amine and subsequent esterification with DHPA to introduce three NH bonds. The triethoxysilyl groups in the precursor were hydrolyzed to silanol groups to condense with their counterparts on silica@Fe₃O₄ NPs. The surface of resultant NPs carried units each contains one QAS site and three N-halamine sites after quaternization and chlorination. The biocidal surface showed superior biocidability against Escherichia coli and Staphylococcus aureus than reported systems due to the improved synergism between multiple antibacterial groups of different types and was stable towards quenching-chlorinating process and storage. The successful design opens insight in the syntheses of more powerful biocides.