O,N-carboxymethyl chitosan–zinc complex: A novel chitosan complex with enhanced antimicrobial activity

Chitosan is a biodegradable, biocompatible and non-toxic deacetylated derivative of chitin. It exhibits myriad of biological activities such as antithrombogenesis, anti-tumor activity, antimicrobial activity, wound healing activity and blood compatibility. Due to the presence of amine (–NH2) groups and hydroxyl (–OH) groups, chitosan can be modified to generate various novel derivatives with varying solubility patterns. Among the various derivatives, O,N-carboxymethyl chitosan has been found to elicit broad range of biological activities and proved to be useful in pharmaceutical applications. Chitosan derivatives form co-ordinate complexes with metal ions like zinc and copper which are also known to have antimicrobial activity. In the present investigation, O,N-carboxymethyl chitosan–zinc complex and chitosan–zinc complex were prepared and characterized using FTIR, XRD and DSC. Further, the complexes were evaluated and compared for antimicrobial activities against Gram-positive and Gram-negative bacteria. The studies revealed that the proposed novel O,N-carboxymethyl chitosan–zinc complex exhibited better antimicrobial activity than chitosan–zinc complex.