Selective and Tunable Galectin Binding of Glycopolymers Synthesized by a Generalizable Conjugation Method

Glycopolymers, conjugates of synthetic polymers with pendant carbohydrates, are becoming increasingly important to probe the role of carbohydrates in cellular processes and for applications like biosensors and drug delivery. A library of glycopolymers bearing different sugar moieties was synthesized by grafting amino-functionalized sugars to poly(acrylic acid) via DMTMM coupling. Primary amines were introduced at the anomeric (C-1) position to a number of unprotected mono-, di-, and trisaccharides using ammonium carbamate and conjugated to poly(acrylic acid) of different molecular weights, synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. This approach provides a simple and efficient route for the preparation of glycopolymers that differ only in the identity or degree of substitution of the sugar moiety on the polymer. The binding parameters (k_a, k_d, and K_D) of these new glycopolymers to galectins-1 and -3 were quantified using surface plasmon resonance. The galectins selectively bound only to lactose-containing polymers, and the binding affinity was dependent on the galectin type, degree of sugar substitution and the molecular weight of polymer chains. Binding to both galectin-1 and -3 increased with a higher degree of sugar substitution, and higher molecular weight of the polymer backbone, reaching K_D values on the order of 10^-11 M.