OBJECTIVETo prepare the poly(lactic-co-glycolic acid) (PLGA) microspheres and composite alginate-chitosan-PLGA microspheres containing superoxide dismutase (SOD) and to evaluate their SOD activities.

METHODSThe SOD-PLGA microspheres were prepared by W/O/W emulsification method, and the composite microspheres were prepared by two steps:alginate-chitosan microcapsules were first prepared by a modified emulsification and ion crosslinking method, and then they were further dispersed in PLGA to form the composite microspheres. The SOD concentration was determined by Coomassie method, its activity was measured by xanthine oxidase system.

RESULTSThe SOD activity was less sensitive to temperature and sensitive to pH, organic solvents, ultrasound and vigorous stir without iced bath. The entrapment efficiencies of SOD in PLGA (50:50) microspheres, PLGA (70:30) microspheres, alginate-chitosan microcapsules, the composite PLGA (50:50) microspheres and the composite PLGA (70:30) microspheres were 36.42%±1.81%, 66.18%±0.05%, 91.08%±1.28%, 87.30%±3.89% and 83.19%±3.48%, respectively. In vitro release tests demonstrated that the SOD activities in 50:50 composite microspheres were higher than that in the PLGA ones at 1 h, 8 h and 1 w.

CONCLUSIONThe composite alginate-chitosan-PLGA microspheres for SOD sustained release can significantly improve the protein entrapment efficiency and maintain its protein activity.