Grafting-density-controlled superhydrophilic chitosan-graft-poly(carboxybetaine methacrylate) coatings for protein-resistant biointerfaces

Chitosan is a renewable and chemically versatile biopolymer, but its use in fouling-prone environments is limited by its tendency to interact with proteins and other biological species. In this work, chains of superhydrophilic zwitterionic poly(carboxybetaine methacrylate) (PCBMA) were grafted onto chitosan to improve its surface hydration and protein resistance. PCBMA homopolymers with different molar masses were synthesized by RAFT polymerization and then grafted onto chitosan using a grafting-to approach. The grafting behavior depended strongly on PCBMA chain length: shorter PCBMA chains led to higher grafting density, while longer chains resulted in lower substitution because of increased steric limitations. CS and CS-g-PCBMA copolymers were then deposited as thin films on silicon oxide wafers by spin coating to evaluate surface morphology, wettability, and protein fouling. The retention of protein was studied with bovine serum albumin (BSA) as model protein. Τhis study showed that length and grafting density of PCBMA control the surface properties of CS-g-PCBMA thin films. Thin films produced from densely grafted CS with short PCBMA chains led to smooth, highly wettable, and protein-resistant chitosan-based coatings. These findings provide a useful strategy for designing hydrated, polysaccharide-based zwitterionic surfaces for antifouling applications.