Insights on the ultra high antibacterial activity of positionally substituted 2′-O-hydroxypropyl trimethyl ammonium chloride chitosan: A joint interaction of -NH2 and -N+ (CH3)3 with bacterial cell wall

The positionally substituted 2'-O-hydroxypropyl trimethyl ammonium chloride chitin (2'-O-HTACCT) with different substitution degree of quaternary ammonium salt were synthesized directly from beta-chitin, after that these 2'-O-HTACCT were then deacetylated to obtain corresponding 2'-O-hydroxypropyl trimethyl ammonium chloride chitosan (2'-O-HTACCS) with different deacetylation degree. The antibacterial activity and mechanism against E. colt and S. aureus of these 2'-O-HTACCT and 2'-O-HTACCS were investigated with various techniques. The results demonstrated that the 2'-O-HTACCT had antibacterial effect against S. aureus, but it had negligible antibacterial effect against E. coli, maybe due to the lack of anionic compound such as teichoic acid on the E. colt's cell wall. Impressively, the high antibacterial effect against E. colt of the 2'-O-HTACCS was derived only from its -NH2, but the ultra high antibacterial effect against S. aureus of the 2'-O-HTACCS was derived both from its -NH2 and -N+ (CH3)(3), and enhanced as its pH value decreased. Thus, the positionally substituted 2'-O-HTACCS played an important role as a high-performance antibacterial bio-resource polymer against E. colt and S. aureus.