Original method for synthesis of chitosan-based antimicrobial agent by quaternary ammonium grafting

Functionalized high molar mass chitosan derivatives with increased antibacterial properties were prepared by the reaction of chitosan with different quaternary ammonium salts. Benzalkonium bromide, pyridinium bromide and triethyl ammonium bromide were synthesized by a quaternization reaction between 1,4-dibromobutane and the respective tertiary amines (N, N-dimethylbenzylamine, triethylamine and pyridine) to obtain three ammonium salts with a bromide end-group capable of reacting with a functional group from the chitosan backbone. The ammonium salts were chemically grafted along the chitosan macromolecular chains. Four different chitosan derivatives were obtained and their chemical structures analyzed and confirmed by ¹H NMR and FT-IR. The corresponding thermal stability was analyzed by TGA. Antibacterial activity has been assessed by determining their minimal inhibitory concentration upon Escherichia coli and Staphylococcus aureus. Furthermore, the antibiogram method was used to complement the antibacterial analysis. The bacteria inhibitory property of the chitosan derivatives exhibited a remarkable improvement compared to unmodified chitosan.