Chitosan-Based Peptidopolysaccharides as Cationic Antimicrobial Agents and Antibacterial Coatings

The rapid spread of multidrug-resistant bacteria has called for effective antimicrobial agents which work on a more direct mechanism of killing. Cationic peptidopolysaccharides are developed in the present work to mimic the peptidoglycan structure of bacteria and to enhance the membrane-compromising bactericidal efficacy. Antimicrobial CysHHC10 peptide was grafted to the C-2 (amino) or C-6 (hydroxyl) position of chitosan backbone via thiol-maleimide "click" conjugation, utilizing the maleimidohexanoic linkers. The peptidopolysaccharide with primary amino backbone intact (CSOHHC) exhibited higher bactericidal activity toward Gram-positive and Gram-negative bacteria, in comparison to that with amino backbone grafted with the peptide (CSNHHC). Both peptidopolysaccharides also exhibited lower hemolytic activity and cytotoxicity than free CysHHC10 peptide due to the moderation effect contributed by the chitosan backbone. For targeting the Gram-positive bacteria in particular, the CSOHHC expressed 4- and 2-fold increases in hemo- and cytoselectivity, respectively, as compared to the CysHHC10 peptide. In an extended application, peptidopolysaccharide antibacterial coatings were formed via layer-by-layer assembly with tannic acid. The peptidopolysaccharide coatings readily killed the adhered bacteria upon contact while being cytocompatible by maintaining more than 60% viability for the adhered fibroblasts. Therefore, the peptidoglycan-mimetic peptidopolysaccharides are potential candidates for anti-infective drugs in biomedical applications.