Hydrophobic PEGylation of Chitosan: A Graft Copolymer Approach toward Developing Nontoxic Antimicrobial Chitosan

Though chitosan-based antimicrobial polymers have been well-known for a long time, selectivity of such derivatives remains always an issue, especially selective bacteria killing using chitosan-derived antimicrobials are far less addressed to the best of our knowledge. In this context, a series of graft copolymers were prepared via chemoselective grafting of acrylate telechelic hydrophobic PEGs onto a chitosan backbone at the C2–NH2 position. The graft copolymers show superior and selective antimicrobial efficacy (with respect to both types of bacteria and RBC) with low toxicity. Based on grafting density, selective bacteria killing was noted between Escherichia coli and Staphylococcus aureus. In the current study, MIC (S. aureus)/ MIC (E. coli) for graft copolymers with a lesser grafting density (CHT-g-OPEG10) is calculated as 1.68, and for graft copolymers with a higher grafting density (CHT-g-OPEG30) MIC (E. coli)/MIC (S. aureus) is reported as 2.14, indicating that CHT-g-OPEG10 may be used preferentially for killing E. coli (with a much lesser effect for S. aureus); whereas CHT-g-OPEG30 may be utilized for the preferential killing of S. aureus (with a much lesser effect on E. coli).