The role of microsphere fabrication methods on the stability and release kinetics of ovalbumin encapsulated in polyanhydride microspheres

The effect of microsphere fabrication methods on the stability and release kinetics of ovalbumin encapsulated in polyanhydride microspheres was investigated. The polyanhydrides used were poly(sebacic anhydride) (poly(SA)) and a 20:80 random copolymer of poly[1,6-bis(p-carboxyphenoxy)hexane] (poly(CPH)) and poly(SA). Microspheres were fabricated using three double emulsion methods (water/oil/water, water/oil/oil and solid/oil/oil) and cryogenic atomization. The encapsulation efficiency was highest for cryogenic atomization and lowest when the w/o/w technique was used. Microspheres fabricated by the s/o/o method had the largest initial burst of released protein. All the methods resulted in zero-order release of the protein after the burst. The release of ovalbumin from poly(SA) and 20:80 (CPH:SA) microspheres lasted ∼3 and ∼6 weeks, respectively. For all fabrication methods the primary structure of released ovalbumin was conserved as determined by gel electrophoresis. The secondary structure of ovalbumin encapsulated in 20:80 (CPH:SA) w/o/w microspheres was not conserved.