Preparation and antibacterial activity of a water-soluble chitosan derivative

Hydroxypropyl chitosan (HPCTS) was synthesized from chitosan and propylene epoxide under alkali condition. It was characterized by Fourier-transform infrared (FTIR), NMR, and elemental analysis. To obtain multiple-derivated chitosan, maleic acid sodium (MAS) was grafted onto HPCTS at 70 T for 2 It in an aqueous solution using ammonium persulfate as an initiator. The grafted copolymer was confirmed by FTIR. At high grafting percentage, good water solubility at various pH values will be obtained. Antibacterial activities of the derivatives against Staphylococcus aureus and Escherichia coli were explored by the cut plug method and the viable cell counting method in sterile distilled water. More than 99.9% of S. aureus and E. coli were killed within 30 min of contact with the derivative HPCTS-g-MAS 3 at the concentration of 100 ng ml(-1). The action was more effective against S. aureus than E. coli, which could be attributed to the fact that the latter has a complicated bilayer cell structure. The mechanism of action should be related to the fact that the derivative has strong coordination capability and its amphiphilic structure. (C) 2002 Elsevier Science Ltd. All rights reserved.