Reversible temperature-responsive and lectin-recognizing glycosylated block copolymers synthesized by RAFT polymerization

Abstract

Reversible temperature-responsive and lectin-recognizing glycosylated block copolymers composed of polyacrylamide (PAAm) and poly(N-isopropylacrylamide) (PNIPAm) were synthesized by consecutive RAFT polymerization reactions. PAAm bearing maltose moieties was synthesized by RAFT polymerization with a trithiocarbonate derivative as a chain transfer agent for chain extension and with N-isopropylacrylamide to obtain block copolymers. The resulting glycosylated block copolymers were responsive to temperature at approximately 33 °C (lower critical solution temperature; LCST) and formed aggregates 100 nm in diameter in aqueous media above the LCST. The aggregates specifically interacted with lectin in aqueous media above the LCST, forming conjugates. When the temperature was decreased below the LCST, the conjugate dissociated into the aqueous medium. The conjugates of block copolymer and lectin were reversible in response to changes in temperature. Glycosylated double-hydrophilic block copolymers composed of polyacrylamide bearing maltose moieties and poly(N-isopropylacrylamide) were synthesized by a RAFT polymerization technique. The resulting glycosylated block copolymer aggregated, interacted strongly with the lectin Con A, and formed a precipitate in aqueous media above the LCST. The precipitate dissociated into the aqueous medium below the LCST. This behavior of the block copolymer in aqueous media is reversible in response to changes in temperature.