Preparation and antibacterial activities of crosslinked chitosan films.

Abstract

Five kinds of chitosan films were prepared in order to study the antibacterial activities against E. coli and St. aureus. Film (1) was prepared by casting of an acetic acid salt of chitosan solution. Films (3) were prepared from film (1) by swelling treatment with aqueous NaOH solutions, and subsequent crosslinking with epichlorohydrin at 85°C for 2 h. Films (4) were prepared from films (3) by treating with a 5% aqueous acetic acid solution. Films (2) and (5) were prepared from film (1) and films (4) by treating with aqueous NaOH solutions, respectively. Film (1) and films (4) indicated antibacterial activities against E. coli and St. aureus. However, films (2), (3) and (5) did not show any antibacterial activities. Film (1) showed a higher antibacterial activity against E. coli and St. aureus than films (4). These results suggest that the antibacterial activities of the films (1) and (4) are dependent on their abilities of the formation of acetic acid salt and also on their structures of acetic acid salt. By the treatment with an aqueous acetic acid solution, the antibacterial activities of films (4) were revealed without a remarkable decrease in the activity after several cyclic treatments with an aqueous NaOH solution and with an aqueous acetic acid solution.