A novel amphiphilic copolymer poly(ethylene oxide-co-allyl glycidyl ether)-graft-poly(epsilon-caprolactone): synthesis, self-assembly, and protein encapsulation behavior

New amphiphilic graft copolymers with hydrophilic poly(ethylene oxide-co-allyl glycidyl ether) (PEAG) as the backbone and hydrophobic poly(epsilon-caprolactone) (PCL) as the side chains (PEAG-g-PCL) were designed and synthesized. For this purpose, the combined techniques of anionic copolymerization, radical mediated thiol-ene reaction and ring-opening polymerization were employed. The properties of the graft copolymer were characterized by H-1 NMR, C-13 NMR, GPC and MALDI-TOF-MS. The self-assembly of the copolymers in aqueous solution was examined by fluorescence spectroscopy, DLS and TEM. The results showed that with a relatively low critical aggregation concentration (CAC), the graft copolymers could form different morphologies including vesicles (polymersomes). The formed polymersomes had the capacity to encapsulate protein molecules (like hemoglobin, Hb) through a modified lyophilization-rehydration method as analyzed via TEM and SDS-PAGE. Furthermore the gas-binding capacity of the encapsulated Hb was assayed via UV-vis spectroscopy. The characteristic absorption peak of the encapsulated Hb in different gas-binding states (CO, O-2, N-2) showed no significant change by comparison with that of free Hb. These Hb encapsulated PEAG-g-PCL polymersomes could have the potential to be applied as an artificial oxygen carrier for transfusion