Article pubs.acs.org/Biomac
N‑Bromo-dimethylhydantoin Polystyrene Resin for Water Microbial Decontamination Oren Aviv,†,‡ Shady Farah,† Nir Amir,‡ Natalia Laout,‡ Stanislav Ratner,‡ and Abraham J. Domb*,† †
Institute of Drug Research, School of Pharmacy-Faculty of Medicine, Center for Nanoscience & Nanotechnology and The Alex Grass Center for Drug Design and Synthesis, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel ‡ Strauss-Water Co, R&D Laboratories, 49527 Petach Tikva, Israel
ABSTRACT: 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.
1. INTRODUCTION
and antiviral activities, and large scale production were not reported. This report is on a detailed large scale synthesis of N-bromo5,5′-dimethylhydantoin polystyrene resin using a simple onepot heterogeneous reaction. Optimized conjugation and bromination conditions were determined and fully characterized using spectral and elemental analysis. Active bromine release from the beads into 650 litters running water and the antimicrobial efficiency was examined against Escherichia coli and MS2.
There are increasing concerns for global healthcare issues regarding microbial infections in a variety of areas such as water purification systems, medical devices, healthcare products, food packaging, and storage.1−5 Antimicrobial polymers have stimulated interest among both academic and industrial researchers, and there have been outstanding developments for several classes of polymers such as the halogenated poly(styrene-divinylbenzenesulfonamides),6,7 polymeric phosphonium materials,8−10 polymeric quaternary ammonium compounds,11−18 and polymeric materials incorporating Nhalamine moieties.19−27 N-halamine compounds have shown excellent efficacies in inactivating a wide range of microorganisms including bacteria, viruses, and fungi in contact times of a few seconds,3,28−32 as well as long-term stability in aqueous solution and in dry storage and rechargeability.33−36 Nhalamine groups such as N-halohydantoins, oxazolidinones, and imidazolidinones were covalently attached to a variety of insoluble polymers used in water-disinfection applications.3,37−40 While N-bromo-hydantoin polystyrene beads have been reported, mainly by the group of Worely,3,5,23−33,37,38 details on the synthesis and spectral characterization, effect of bead degree of cross-linking, bromination conditions, detailed antibacterial © XXXX American Chemical Society
2. MATERIALS AND METHODS 2.1.1. Materials. All reagents and solvents were of analytical grade and purchased from Sigma-Aldrich, Rehovot, Israel: isobutyl alcohol anhydrous 99.5%, 5,5-dimethylhydantoin 98%, potassium hydroxide, sodium hydroxide, ethanol, bromine ≥99%, acetic acid glacial. Chloromethyl polystyrene resin was received from PUROLITE Company: pore volume: 0.33 mL/g; pore diameter: 743 Å; surface area: 10 m2/g; Cl: 4.42 eq/kg. The hypobromous acid solution was prepared by bromine addition to an aqueous hydroxide solution followed by acetic acid titration to achieve pH 6.5. Received: February 21, 2015
A
DOI: 10.1021/acs.biomac.5b00249 Biomacromolecules XXXX, XXX, XXX−XXX
Article
Biomacromolecules
Scheme 1. Brominated Hydantoin Grafted Polystyrene Resin Synthesis Includes Two Major Steps: (1) Conjugation Reaction between Chloromethyl Polystyrene Resin and in Situ Prepared Hydantoin Salt in Isobutyl Alcohol at Reflux for 20 h and (2) Bromination of Conjugated Polystyrene Resin by Reaction with Prepared Hypobromous Acid for at Least 24 h
2.2. Methods. 2.2.1. Brominated Hydantoin Grafted Polystyrene Resin Synthesis (Br-DMH-Ps). The synthetic procedure for antimicrobial polymer Br-DMH-Ps was quite straightforward. It is illustrated in Scheme 1. The procedure includes two steps: 5,5′-dimethylhydantoin conjugation on polystyrene resin followed by bromination with freshly prepared hypobromous acid solution. The chloromethyl polystyrene resin is prewashed in acetone and dried before use. First, conjugation of 5,5′-dimethylhydantoin (DMH) on chloromethyl polystyrene resin (PS-Cl) is formed in isobutyl alcohol (IBA). Then, equal molar 5,5′-dimethylhydantoin reacts with potassium hydroxide to yield soluble 5,5′dimethylhydantoin salt with reflux conditions to achieve a clear solution. A calculated amount of DMH salt (see eq 1) is dissolved in the solvent (148.8 g/L DMH salt in IBA), then chloromethyl polystyrene is added (41.6 g/L IBA) under an inert environment using nitrogen gas. Stirring of the reaction continues at reflux for 20 h, then it is cooled to room temperature, and conjugated resin is separated by filtration and washed several times with boiling reverse osmosis treated (RO) water. In the second step, N-bromination is as follows: sodium hydroxide is carefully added to ice-cold RO water (7.5 >7.5 7.3 >7.2 6.7 6.7 5.9 7.5 4.4 >4.9 4.8 >4.7 3.6 3.4 3 7.5 4.9 NTb NT NT NT NT NT NT
3.8 2.9 3.3 NT NT NT NT NT NT NT
>7.5 >7.5 >7.3 >7.2 7.1 7.5 7.5 5.6 4.4 >4.9 >4.8 4.7 4.5 4.3 3 4.9 4.4 4.7 3.1 2.4 2.6 NT NT
>7.5 5 5.3 NT NT NT NT NT NT NT
>4.4 3.1 3.6 NT NT NT NT NT NT NT
a All the Columns were identical and fitted with 16 g of brominated beads in the following order, Column A: (10 h, 1:3, 72 h), Column B: (20 h, 1:1.5, 72 h), Column C: (20 h, 1:3, 72 h), Column D: (20 h, 1:3, 24 h), Column E: (20 h, 1:1.5, 24 h). bNT-not tested because experiment was stopped for tested material (low antimicrobial efficacy).
E
DOI: 10.1021/acs.biomac.5b00249 Biomacromolecules XXXX, XXX, XXX−XXX
Article
Biomacromolecules
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bromination for 72 h and at ratio 1:3 (20 h conjugation reaction) exhibited excellent antimicrobial properties: 6 and 4 log reduction for E. coli and MS2, respectively, were obtained for all tested points during 250 L, and the tested resins maintained their activity for 550 L. This brominated resin should be considered in filters for decontamination of drinking water.
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AUTHOR INFORMATION
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[email protected]; Tel.: +972-2 675 7573; Fax: +972-2 675 7076. Notes
The authors declare no competing financial interest.
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REFERENCES
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DOI: 10.1021/acs.biomac.5b00249 Biomacromolecules XXXX, XXX, XXX−XXX
