A simple methodology for the synthesis of heterotelechelic protein–polymer–biomolecule conjugates

Abstract

AbstractA synthetic protocol for the preparation of hetero‐biofunctional protein–polymer conjugates is described. A chain transfer agent, S,S‐bis (α,α′‐dimethyl‐α″‐acetic acid) trithiocarbonate was functionalized with α,ω‐pyridyl disulfide (PDS) groups, Subsequently, one of the PDS groups was covalently attached to bovine serum albumin (BSA) at the specific free thiol group on the cysteine residue through a disulfide linkage. The second PDS group remained intact, as it was found to be inaccessible to further BSA functionalization. The BSA‐macro‐reversible addition‐fragmentation chain transfer (RAFT) agent was then used to prepare BSA‐polymer conjugates via in situ polymerization of oligo (ethyleneglycol) acrylate and N‐(2‐hydroxypropyl) methacrylamide using an ambient temperature initiator, 4,4′‐azobis [2,9‐imidazolin‐2‐ethyl)propane] dihydrochloride in an aqueous medium. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) confirmed that the in situ polymerization occurred at the protein surface where the RAFT agent was attached and the molecular weights of the BSA–polymer conjugates were found to increase concomitantly with monomer conversion and polymerization time. After polymerization the remaining terminal PDS groups were then utilized to attach thiocholesterol and a flurophore, rhodamine B to the protein–polymer conjugates via disulfide coupling. UV–Vis and fluorescence analyses revealed that ∼80% of the protein conjugates were found to retain integral PDS end groups for further attachment to free thiol‐tethered precursors. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1399–1405, 2010