Synthesis of Heterotelechelic Polymers for Conjugation of Two Different Proteins

We describe a straightforward approach to synthesize polymers with end-groups that bind site-specifically to two different proteins. Telechelic biotin−maleimide poly( N -isopropylacrylamide) (pNIPAAm) was synthesized for the formation of streptavidin (SAv)−bovine serum albumin (BSA) polymer conjugates. Reversible addition−fragmentation chain transfer (RAFT) polymerization of NIPAAm was conducted in the presence of biotinylated chain transfer agents (CTAs) with either ester or amide linkages, and the resultant α-biotinylated pNIPAAms were formed with low polydispersity indices (PDI ≤ 1.09). UV−vis analysis of the trithiocarbonate chain-ends indicated 88% or greater retention of the group. A maleimide was introduced to the ω chain-end via a radical cross-coupling reaction with a functionalized azo-initiator. The polymer structures were characterized by 1 H NMR spectroscopy and gel permeation chromatography (GPC). The resultant biotin−maleimide heterotelechelic polymer was used to form a SAv−BSA heterodimer conjugate. Bioconjugate formation was confirmed by gel electrophoresis.