Effect of Osmotic Pressure in the Solvent Extraction Phase on BSA Release Profile from PLGA Microspheres

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Abstract
This study investigated the influence of osmotic pressure in the organic solvent extraction phase on release profile of bovine serum albumin (BSA) from poly(lactide-co-glycolide) (PLGA) microspheres. BSA-loaded PLGA microspheres with a target load of 10% were prepared by a double emulsion phase separation method. All the microsphere batches were fabricated in the same conditions except that in the organic solvent (CH2Cl2) evaporation step. Different concentrations of NaCl (0, 1.8, and 3.6%) or sucrose (20%) were used to generate a range of osmotic pressures in the extraction aqueous phase. These microspheres were characterized for incorporation efficiency, surface and internal morphology, particle size, protein stability, and in vitro release. The microspheres were spherical with particle size ranging from 16.8 to 27.8 μm. Higher osmotic pressure resulted in a denser internal structure although similar nonporous surface morphology was observed with all batches. No significant difference in encapsulation e...