Sustained release of bee venom peptide from biodegradable thermosensitive PLGA-PEG-PLGA triblock copolymer-based hydrogels in vitro.

Biodegradable thermosensitive poly (DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers with DL-lactide/glycolide molar ratio ranging from 6/1 to 15/1 were synthesized from monomers of DL-lactide, glycolide and polyethylene glycol and were evaluated for sustained release of bee venom peptide in vitro. The resulting copolymers are soluble in water to form free flowing fluid at room temperature but become hydrogels at body temperature. The gelation temperature of the copolymer solutions can be influenced by the concentration and DL-lactide/glycolide molar ratio of the copolymers. The release of bee venom peptide from the copolymer-based hydrogel and hydrogel degradation in the phosphate buffer (pH 7.4) was studied at 37 degrees C under agitation. Bee venom peptide was released from the copolymer-based hydrogels over 40 days in vitro and the variation of DL-lactide/glycolide molar ratio in the PLGA block of the copolymer did not significantly affect the release rate of bee venom peptide (P > 0.05). The hydrogels undergo slower degradation and then faster degradation rate during the whole release stage. Accordingly, the mechanism of bee venom peptide was Fickian diffusion during initial stage and then may be a combination of diffusion and degradation. The synthesized copolymers have the advantage of gelation temperature over the ReGel system. These results indicate that the PLGA-PEG-PLGA copolymer-based hydrogel could be a promising platform for sustained delivery of bee venom peptide.