STABILITY OF BSA ENCAPSULATED INTO PLGA MICROSPHERES USING PAGE AND CAPILLARY-ELECTROPHORESIS

Bovine serum albumin (BSA, M-w 66200 Da) has been encapsulated as a mo del protein drug within poly(D,L-lactide-co-glycolide) (PLGA 50:50) mi crospheres using a w/o/w double emulsion method. The microspheres prep ared were smooth and spherical with a mean particle size of 1.32 mu m. The total protein loading and surface-associated protein were 8.61 an d 16.60%, respectively. The microspheres showed a triphasic in vitro r elease profile with an initial burst effect due to the release of the protein adsorbed on the microsphere surface, a second sustained releas e phase due to protein diffusion through the pores or channels formed in the polymer matrix, and a third phase due to polymer bioerosion. Th e purpose of this paper was to evaluate the effect of the microencapsu lation process on the integrity of the entrapped protein using polyacr ylamide gel electrophoresis and capillary electrophoresis. The stabili ty of the protein released during in vitro assays was also assessed. T he results obtained showed that there was no apparent effect of the dr astic encapsulation conditions (contact with dichloromethane (DCM), pr obe sonication, and vigorous shaking) on the structural integrity of t he protein. On the other hand, it was found that after 1 week of incub ation the protein released from the microspheres starts to hydrolyze t o smaller fragments, probably due to a significant decrease in the med ium pH as a result of the accumulation of the polymer degradation prod ucts. (C) 1998 Elsevier Science B.V. All rights reserved.