Potential Antibacterial Activity of Polystyrene Nanoparticles/Chitosan Coated on Cotton Fabrics Krisana Siralertmukul, 1 Supawin Watcharamul, 2 Natthakrita Wicheanpaisan, 2 Roongkan Nuisin* 2 Summary: This research is to study the potential of using polystyrene nanoparticles and chitosan solution to increase the anti-bacterial activity on cotton fabrics prepared by a conventional pad-dry-cure method. Firstly, cotton fabrics were coated with chitosan solutions at the concentrations of 0.1, 0.5, and 1.0 (%w/v) and tested for the antibacterial property which was determined by clear zone measurement and viable count assay using Escherichia coli (ATCC 25922) as a tested microorganism. The results showed that, the percentage bacterial reductions were 87.2, 86.3, and 48.5%, respectively, when the cotton fabrics was coated only with chitosan solution. When polystyrene nanoparticle solution was coated onto cotton fabrics prior to coating with chitosan solutions at the concentrations of 0.1, 0.5, and 1.0 (%w/v), the percentage bacterial reductions were 90.3, 90.8, and 65.5%, respectively. This indicated that coating the cotton fabrics with polystyrene nanoparticles prior to chitosan coating would remarkably increase the antibacterial activity. The scanning electron micrographs showed that polystyrene nanoparticles were aggregated and inserted in between the interfiber spacings. The thin film of chitosan was also observed on the surface of cotton fabrics and hydrophobic property of the fabrics was tested via contact angle measurement. Keywords: chitosan; cotton; inhibition zone; nanoparticles; pad-dry-cure Introduction Cotton is natural fiber recalcitrant to microbial decomposition. Biodegradation of the (1!4)- b-D-glucan of cellulose results from the action of cellulolytic enzymes produced widely by bacteria and fungi. [1,2] Cotton fibers have chemical bonds which could be readily hydro- lyzed by microorganisms. [3] Bacterial growth could lead to fiber degradation thereby causing decreases in tensile strength, elongation, elasticity, and discoloration of fabric materials. Chitosan is the renewable, nontoxic and biodegradable polymer obtained from marine products i.e. shrimp shell, crab, and squid pen. [4] Chitosan is a polysaccharide composed of (1!4)-2-amino-2-deoxy-b-D-glucan which is a derivative of chitin [b(1!4)-2-acetamido- 2-deoxy-b-D-glucan] via N-deacetylation process, and is consequently a copolymer of N-acetylglucosamine and glucosamine. [5] Chitosan has a wide range of biological activities, especially antibacterial properties. It promotes the aggregation of bacterial cells leading to disorganization of their cell wall and cytoplasmic membrane. [6] In acidic solvents, the NH 2 group in chitosan becomes a protonated amino group and allows then modi fied chitosan to inhibit both the gram- negative and gram-positive bacteria. [7,8] Chitosan is considering as cationic polymer, and consequently forms film. [9] It was also reported that chitosan can be used as finishing materials for polyester fabric to enhance antimicrobial activity. [10] A report on the 1 Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok 10330, Thailand 2 Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand Fax: (þ66) 022185180; E-mail: Roongkan.N@Chula.ac.th Macromol. Symp. 2015, 354, 324–333 DOI: 10.1002/masy.201400081 324 | ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com