Electrospray encapsulation of water-soluble protein with polylactide. I. Effects of formulations and process on morphology and particle size

Bovine serum albumin (BSA) was encapsulated with poly (lactide) (PLA) using an electrospray technique in which a sufficiently strong electric field was applied to overcome the surface tension of a droplet and to produce small particles. The influences of PLA solvent type, PLA solution concentrations; the viscosity, electrical conductivity and surface tension of PLA solutions and PLA/BSA emulsions; and the applied voltage and flow rate on the morphology and size of the BSA-loaded PLA particles were examined. 1,2-dichloroethane (DCE) was a better solvent for PLA than dichloromethane. Spherical electrosprayed particles, with smooth surfaces, were observed with both solvents. The electrical conductivity increased and particle size decreased when acetone was mixed with DCE as PLA solvent. However, the particles were no longer spherical. The size of the particles increased and shape became spherical as PLA concentration was increased from 1-3%. Increasing the concentration to 4% resulted in the formation of a mixture of beads and fibres. Particle size decreased as applied voltage was increased from 10-15kV and increased as flow rate was increased from 0.5-3 ml h(-1).