Electrospray encapsulation of water-soluble protein with polylactide : Effects of formulations on morphology, encapsulation efficiency and release profile of particles

Bovine serum albumin (BSA)-loaded poly(lactide) (PLA) particles were prepared using an electrospraying technique, in which a sufficiently strong electric field was applied to overcome the surface tension of a droplet. A comprehensive investigation was conducted on the effects of independent variables organic/aqueous phase volume ratio and BSA/PLA weight ratio on the dependent variables viscosity, electrical conductivity, surface tension; the morphologies, sizes, and yields of particles; BSA encapsulation efficiency (EE); and in vitro release. An increase in the organic/aqueous phase ratio increased the viscosity and decreased the electrical conductivity of the emulsions, while the viscosity increased with BSA/PLA ratio. In general, spherical particles, with smooth surface and without visible pores, were observed. However, the spherical shape was lost as the organic/aqueous phase ratio decreased and the BSA/PLA ratio decreased. The particle sizes ranged from 0.84 ± 0.18 to 3.95 ± 0.51 μm and the yield was in the range of 64.3 ± 1.8 to 80.1 ± 2.6%. EE of BSA was between 22.9 and 80.6%, and was increased with organic/aqueous phase ratio and decreased with increasing BSA/PLA ratio. In vitro release of BSA from the particles was reduced with increasing organic/aqueous phase ratio and was enhanced by the increase in the BSA/PLA ratio.