Antibacterial effects of amino acids-grafted water-soluble chitosan against drug-resistant bacteria

Chitosan is an available natural polysaccharide that is biocompatible, biodegradable, and non-toxic. In this study, to enhance the antibacterial activity of water-soluble chitosan (WSC), amino acids with hydrophobic, anionic, or cationic side chains were grafted to the amine groups of WSC (amino acid-grafted WSC; AGW). Chemical characterization of AGW was performed by H-1 nuclear magnetic resonance spectroscopy, resulting in grafting molecular percentages of 7.3 similar to 9.9%. AGW exhibited more potent antibacterial activity than unmodified WSC in both drug-susceptible and drug-resistant bacteria. Scanning electron microscopy and a calcein leakage assay in bacteria and artificial liposomes, respectively, revealed the antibacterial action of AGW to be membranolytic. Lysine or isoleucinegrafted WSC showed potent in vivo antibacterial activity in a drug-resistant Pseudomonas aeruginosa-infected mouse model. AGW has potential use as an effective antibacterial agent.