Carboxylic Acid End-Capped Brushes on Titanium via Interface-Mediated RAFT Polymerization and Cell-Surface Interactions

Polymer brushes with tailored surface functionalities are important materials to manipulate the interactions between cells and surfaces in a biomedical context. To enhance the control of the conjugation of cell-adhesive peptides to the polymer brush terminus, poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) brushes were fabricated via interface-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization on titanium substrates. Due to the immobilization of 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid as a chain transfer agent (CTA) on the titanium substrates before the subsequent RAFT polymerization, terminal carboxylic acid groups were introduced in the brushes. The brushes obtained were characterized by ellipsometry, static water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy. PDEGMA brushes allow the facile conjugation of peptides containing the arginine-glycine-aspartic acid (GRGDS) sequence, which afforded the peptide-specific attachment of NIH 3T3 fibroblasts. By contrast, the inhibition of cell attachment was observed on PDEGMA brushes with 7 nm dry thickness conjugated with arginine-alanine-aspartic acid (GRADS). The strategy of surface functional group modification with controllable antifouling or cell-adhesive properties will allow a versatile bio-functionalization approach independent of the underlying surface condition as polymeric biomaterials, among others, in titanium-based medical implant devices.