New biodegradable polymers for delivery of bioactive agents

Biodegradable, thermosensitive triblock copolyiner, PLGA-PEG-PLGA, can be easily fabricated into drug-loaded microspheres or injectable in situ hydrogel system for protein or water-insoluble drugs without use of organic solvent. Aqueous-based microsphere exhibited continuous release of intact insulin in vitro for 3 weeks while the microspheres prepared using dichloromethane showed initial burst and incomplete release. Confocal miscoscopy images of microspheres corroborated the release pattern. Next study with an injectable in situ hydrogel (ReGel(TM)) exhibited zero-order insulin release in vitro and sustained plasma insulin level for 2 weeks in vivo upon single subcutaneous injection in SD rats.