Synthesis of functional polymer brushes containing carbohydrate residues in the pyranose form and their specific and nonspecific interactions with proteins

Abstract

Three novel N-substituted acrylamide monomers containing different carbohydrate residues, 2'-acrylamidoethyl-α-d-mannopyranoside, 2'-acrylamidoethyl-β-d-glucopyranoside, and 2'-acrylamidoethyl-β-d-galactopyranoside, in the pyranose form were synthesized. The corresponding glycopolymer brushes were prepared on silicon substrates by surface-initiated atom transfer radical polymerization (SI-ATRP) using unprotected glycomonomers. The formation of glycopolymer brushes was well-characterized using ellipsometry, ATR-FTIR, water contact angle analysis, atomic force microscopy analysis, and X-ray photoelectron spectroscopy. The effects of halogen, ligand, and solvent on the polymerization were thoroughly investigated. It was shown that CuCl/CuCl2/tris(2-dimethylaminoethyl)amine (Me6TREN) catalytic system with an optimized ratio of Cu(I)/Cu(II) produced glycopolymer with high molecular weight (Mn = 44-140 kDa) and relatively narrow molecular weight distribution (PDI = 1.4). The dry thickness of resulting glycopolymer brushes (10-36 nm) showed a proportional relationship with the molecular weight of free polymer generated in the solution. The grafting densities of obtained glycopolymer brushes were between 0.12 and 0.17 chains/nm(2). The grafting of glycopolymer resulted in highly hydrophilic surface layer with very low water contact angles (<10°). The glycopolymer brushes showed ultralow protein adsorption from bovine serum albumin (BSA) and fibrinogen (Fb) solutions. Glycopolymer brushes containing glucose units showed relatively better protection against BSA and Fb adsorption than those brushes containing mannose and galactose units. Synthesized glycopolymer brushes retained specific protein interactions, as evident from the interaction with Concanavalin A (Con A). The interaction of surface-grafted glycopolymer brushes with Con A depended on both the stereochemistry of carbohydrate units and the chemical structures present. In addition, the newly synthesized glycopolymer brushes performed significantly better in comparison with currently available structures in terms of specific protein interactions.