Synthesis of Aminooxy End-Functionalized pNIPAAm by RAFT Polymerization for Protein and Polysaccharide Conjugation

A Boc-protected aminooxy end-functionalized poly(N-isopropylacrylamide) (pNIPAAm) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The monomer was polymerized in the presence of a Boc-protected aminooxy trithiocarbonate chain transfer agent (CTA) utilizing 2,2'-azobis(2-isobutyronitrile) (AIBN) as the initiator in dimethylformamide (DMF) at 70 degrees C. The Final polymer had a number-average molecular weight (M-n) of 4200 Da as determined by H-1 NMR spectroscopy and a narrow polydispersity index (1.14) by gel permeation chromatography (GPC). The Boc group was removed, and the polymer was then incubated with N'-Ievulinyllysine-modified bovine serum albumin (BSA). Gel electrophoresis confirmed that the conjugation was successful. The aminooxy end-functionalized pNIPAAm was also immobilized on it gold surface after reduction of the trithiocarbonate end-group. The pNIPAAm surface was then incubated with all aldehyde-modified heparin to yield the polysaccharide-functionalized surface. All surface modifications were monitored by FT-IR spectroscopy.