Morphological and structural properties of two-phase coaxial jet electrosprayed BSA-PLA capsules

Bovine serum albumin (BSA) was encapsulated with poly (lactide) (PLA) using a two-phase coaxial jet electrospray technique in which two immiscible liquids were injected separately through two concentrically located and electrified capillary needles under a sufficiently strong electric field. BSA acted as the driving liquid due to its high electrical conductivity, while the high viscosity of the PLA and low interfacial tension of the PLA and BSA solutions favoured the formation of stable cone-jets. The morphology of the particles was changed from irregular to fully spherical with smooth surfaces when the PLA concentration increased from 1 to 5%. The effects of the PLA concentration and flow rate and applied voltage on particle size were statistically significant. Particle size increased as PLA concentration increased from 2 to 3.5% and decreased as the applied voltage was increased from 15 to 19 kV. No BSA melting peak was detected in DSC plot and BSA exhibited an amorphous or disordered-crystalline state in the PLA micoparticles, while FTIR results indicated that the secondary structure of the BSA was preserved.