Fabrication of microspheres using blends of poly(ethylene adipate) and poly(ethylene adipate) / poly(hydroxybutyrate-hydroxyvalerate) with poly(caprolactone): Incorporation and release of bovine serum albumin

Spherical microspheres composed of polymer blends 80:20 PEAD/PCL II and 40:40:20 PEAD/P(HB-HV)/PCL II containing a range of BSA loadings have been fabricated using a single emulsion technique with solvent evaporation. 80:20 PEAD/PCL II microspheres had smooth surfaces while 40:40:20 PEAD/P(HB-HV)/PCL II microspheres consisted of a mixture of smooth surfaced, microporous and macroporous microsphere fractions. Irrespective of fabrication polymer, microspheres were produced in high yield (> 75%) and BSA incorporation had no significant effect on microsphere size distribution which ranged from 0.6 to 5 microns and from 2.1 to 50 microns for 80:20 PEAD/PCL II and 40:40:20 PEAD/P(HB-HV)/PCL II microspheres, respectively. The loss of BSA by partitioning into the aqueous phase resulted in low encapsulation efficiencies (< 14.5%). BSA release increased significantly with the-oretical percentage loading but the relationship could not be confirmed when the total cumulative release of BSA was expressed as a percentage of the actual total BSA incorporated. Significant BSA release could be detected for up to 26 days.