Switchable Antimicrobial and Antifouling Coatings from Tannic Acid-Scaffolded Binary Polymer Brushes

Surface biofouling has been a serious environmental and ecological problem for centuries. In this study, pH-sensitive poly(2-diisopropylaminoethyl methacrylate)-b-poly(2-methacryloyl-oxyethyl phosphorylcholine) (PDPA-b-PMPC) and cationic polylysine (PLYS) chains are grafted on tannic acid (TA). The resulting PLYS-TA-PDPA-b-PMPC can be anchored in "one-step", via coordination chelation of TA, on substrate surfaces to impart the latter with switchable antimicrobial and antifouling functionalities. The PLYS-TA-PDPA-b-PMPC functionalized stainless steel (SS) surface exhibits significant antimicrobial (S. epidermidis and E. coli) activity as well as resistance to protein adsorption, bacterial adhesion, and microalgal (Amphora coffeaeformis) attachment. The reversible transition between antimicrobial and antifouling effects is achieved in response to pH changes of the surrounding environment. Decrease in pH arising from bacterial adhesion/deposition switches the antimicrobial polymer brush coatings to the antifouling mode with "self-defensive" (fouling-release/self-cleaning) capability. The functional polymer coatings exhibit low cytotoxicity. They are sustainable over 30 days of stationary exposure to filtered seawater or 14 days under flowing seawater. Therefore, the switchable antimicrobial/antifouling polymer brush coatings, with environmentally benign TA anchor and environmentally responsive fouling-release ability, are potentially useful for biofouling inhibition in biomedical and marine environments.