Preparation and Biological Effects of Amphiphilic Thermoresponsive Hydrogels for Ocular Drug Delivery

A novel amphiphilic block copolymers of methoxypoly (ethylene glycol)-b-poly(lactic-co-glycolic acid) were synthesized by the ring-opening polymerization of methoxypoly (ethylene glycol), D, L-lactide, glycolide, crosslinked with 2,2-bis (2-oxazoline) and the chemical structures were identified by H-1 NMR and GPC. Phase transition behavior was observed. Physicochemical characterization was evaluated, including the thermo-sensitive behavior, critical micelle concentration, particle size and the drug release profile. Biodegration and cytocompatibility were assessed in vitro. This new material showed a lower critical micelle concentration and thermogelling phase transition behavior. Thermoresponsive hydrogels exhibited a fast and reversible sol-gel-sol phase change with alteration in temperature. The release rate of anti-VEGF drug (bevacizumab) entrapped in hydrogels was examined in vitro. Release profile of the bevacizumab was showed that there was sustained release for approximately 30 days. Released bevacizumab inhibited the RF6A cells growth, which showed the bioactivity of anti-VEGF agent maintenance in the hydrogels within the release process. The characteristics of noncytotoxicity, biodegradability and bioactivity as well as thermoresponsive behavior appear to be a promising ocular drug delivery system.