Chitosan is a natural based biopolymer, obtained by alkaline deacetylation of chitin, which presents excellent biological properties such as biodegradability and immunological, antibacterial and wound-healing activity. Recently, there has been a growing interest in the chemical modifification of chitosan in order to improve its solubility and widen its applications. The amino group of chitosan has been modified to assess its anti-microbial activity. Here, we report a hydrogel based on glucosamine conjugated chitosan which has excellent antimicrobial efficacy against Escherichia coli. The grafting of cationic charges on surface of chitosan was found to tailor the surface charge, thus balancing electrostatic interactions affecting the cell behaviour.