Dextran- and Chitosan-Based Antifouling, Antimicrobial Adhesion, and Self-Polishing Multilayer Coatings from pH-Responsive Linkages-Enabled Layer-by-Layer Assembly

To meet the demand for more environmentally friendly antifouling coatings and to improve fouling-resistant coatings with both "offense" and "defense" functionalities, polysaccharides (PSa)-based self-polishing multilayer coatings were developed for combating biofouling. Dextran aldehyde (Dex-CHO) and carboxymethyl chitosan (CMCS) were synthesized and alternatively incorporated via imine linkage into the multilayer coating in layer-by-layer (LbL) deposition. Surface plasmon resonance (SPR) technique was utilized to monitor the LbL assembly process. With increasing number of assembled bilayers, the antifouling performances against bovine serum albumin (BSA) adsorption, bacterial (S. aureus and E. coli) adhesion, and alga (Amphora coffeaeformis) attachment improved steadily. The self-polishing ability of the multilayer coatings was achieved via cleavage of pH-responsive imine linkage under acidic environments. As such, dense bacterial adhesion induced detachment of the outmost layer of the coatings. The efficacies of antifouling and antimicrobial adhesion were thus enhanced by the self-polishing ability of the multilayer coatings. Therefore, the LbL-deposited self-polishing dextran/chitosan multilayer coatings offer an environmentally friendly and sustainable alternative for combating biofouling in aquatic environments.