Trehalose Glycopolymers for Stabilization of Protein Conjugates to Environmental Stressors

Abstract

Herein, we report the synthesis of trehalose side chain polymers for stabilization of protein conjugates to environmental stressors. The glycomonomer 4,6-<i>O</i>-(4-vinylbenzylidene)-α,α-trehalose was synthesized in 40% yield over two steps without the use of protecting group chemistry. Polymers containing the trehalose pendent groups were prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization using two different thiol-reactive chain transfer agents (CTAs) for subsequent conjugation to proteins through disulfide linkages. The resulting glycopolymers were well-defined, and a range of molecular weights from 4200 to 49 500 Da was obtained. The polymers were conjugated to thiolated hen egg white lysozyme and purified. The glycopolymers when added or covalently attached to protein significantly increased stability toward lyophilization and heat relative to wild-type protein. Up to 100% retention of activity was observed when lysozyme was stressed ten times with lyophilization and 81% activity when the protein was heated at 90 °C for 1 h; this is in contrast to 16% and 18% retention of activity, respectively, for the wild-type protein alone. The glycopolymers were compared to equivalent concentrations of trehalose and poly­(ethylene glycol) (PEG) and found to be superior at stabilizing the protein to lyophilization and heat. In addition, the protein–glycopolymer conjugates exhibited significant increases in lyophilization stability when compared to adding the same concentration of unconjugated polymer to the protein