1241 The Polymer Society of Korea www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673 Macromolecular Research, Vol. 21, No. 11, pp 1241-1246 (2013) Preparation and Characterization of Chlorinated Cross-Linked Chitosan/Cotton Knit for Biomedical Applications Hye Kyoung Shin 1 , Mira Park 3 , Yong Sik Chung 3 , Hak-Yong Kim * ,3 , Fan-Long Jin 2 , Heung-Soap Choi 4 , and Soo-Jin Park * ,1 1 Department of Chemistry, Inha University, Incheon 402-751, Korea 2 Department of Polymer Materials, Jilin Institute of Chemical Technology, Jilin City 132022, P. R. China 3 Department of Textile Engineering, Chonbuk National University, Jeonbuk 561-756, Korea 4 Departments of Mechanical and Design Engineering, Hongik University, Sejong 339-701, Korea Received February 7, 2013; Revised April 17, 2013; Accepted April 28, 2013 Abstract: A new cross-linked chitosan/cotton knit was prepared by the chlorination of chitosan under acidic conditions, and its active chlorine content, mechanical and antimicrobial properties, and rechargeability were characterized. The active chlorine content of the chitosan/cotton knit increased with the concentration of chitosan or sodium hypochlorite used for the treatment and showed a slight decrease upon repeated laundering. The cross-linked chitosan/cotton knit displays lower stress and higher strain than pristine cotton knit. The chlorination of the chitosan/cotton knit resulted in powerful antimicrobial activity against both gram-negative and gram-pos- itive bacteria. For up to 30 days of storage the knit showed excellent rechargeability, taking up chlorine to nearly initial levels. Scanning electron microscope (SEM) observations indicated that chlorination did not cause the damage to the cross-linked chitosan/cotton knit. Keywords: chitosan, cotton knit, N-halamine, active chlorine content, antimicrobial activity. Introduction Bacterial contamination of fabric is an important issue in the medical industry, causing infections in patients and employ- ees; cross-infections can occur because of contamination of carpet, beds, accessories, and other items. Hospital gowns and uniforms are an important defense against bacteria, but these items are not foolproof. 1-8 N-Halamines contain one or more nitrogen-halogen cova- lent bonds formed by the halogenation of imides, amides, or amines. N-Halamines have shown almost instant biocidal activity against a wide range of micro-organisms without caus- ing environmental concerns. It is generally believed that the biocidal action of N-halamines is caused by the transfer of positive halogens from N-halamines to the appropriate recep- tors in the cell. This process can effectively destroy or inhibit enzymatic or metabolic cell processes, causing cell death. The active chlorines consumed during halogen transfer can be recharged with chlorine from a subsequent bleach treat- ment. 9-13 Liu et al. studied the grafting of amide monomers onto cotton cellulose and the subsequent chlorination of the grafted materials. The chlorinated acyclic N-halamine cotton cellu- lose provided rapid inactivation against Escherichia coli (a gram-negative bacterium). 14 Ren et al. demonstrated that an antimicrobial coating of an N-halamine biocidal monomer could be applied to cotton fibers via admicellar polymeriza- tion. After chlorination with sodium hypochlorite solution, the polymer-coated cotton fabrics effectively inactivated both Staphylococcus aureus (a gram-positive bacterium) and E. coli after relatively brief contact times. 15 Antimicrobial N-halamine-modified chitosan films were investigated by Li et al., who found that the chlorinated films showed good efficacy against the two bacterial species (S. aureus and E. coli) with log reductions of 7.4 and 7.5 within 10 and 5 min of contact time, respectively. 16 The preparation, character- ization, and antimicrobial function of N-halamine-based chito- san were further examined by Cao et al., who transformed the amino groups in chitosan into N-halamine structures by chlorine bleach treatment. 17 In this study, a cross-linked chitosan/cotton knit was prepared by padding amine group-functionalized cross-linked chitosan onto a cotton knit, and subsequently chlorinating the chitosan/ cotton knit via N-halamine to improve its antimicrobial activity. The chlorinated cross-linked chitosan/cotton knit was characterized with respect to its mechanical strength, surface properties, antimicrobial activity, and rechargeability. DOI 10.1007/s13233-013-1164-9 *Corresponding Authors. E-mails: khy@chonbuk.ac.kr or sjpark@inha.ac.kr