Fabrication of microcapsules using poly(ethylene adipate) and a blend of poly(ethylene adipate) with poly(hydroxybutyrate-hydroxyvalerate): incorporation and release of bovine serum albumin

Spherical reservoir-type microcapsules composed of poly(ethylene adipate) (PEAD) and 20% poly-ɛcaprolactone (PCL II), poly(hydroxybutyrate-hydroxyvalerate) (P(HB-HV)); 10.8% HV) 20% PCL II and a blend of P(HB-HV)/PEAD 20% PCL II containing bovine serum albumin (BSA; surrogate protein)-loaded agarose have been fabricated using a double emulsion technique with solvent evaporation. P(HB-HV) and PEAD microcapsules had microporous and smooth surfaces, respectively, while blend microcapsules contained a mixture of the two. Irrespective of the fabrication polymer, microcapsules were generated in high yield (>75%) and BSA incorporation had no significant effect on microcapsule size distribution (8–200 μm). The loss of BSA, both by partitioning into aqueous continuous phase and through the micropores of P(HB-HV) microcapsules as BSA-loaded agarose during the precipitation of the fabrication polymer concomitant with solvent evaporation, resulted in low encapsulation efficiencies (< 15%). In all cases BSA release could be monitored for up to 26 d and the amount and duration of BSA release from P(HB-HV) 20% PCL II microcapsules was influenced as much by micropore number and diameter as by the extent of reservoir loading, while BSA release from smooth PEAD microcapsules was assumed to be the result of an acute increase in membrane porosity.