Polyanhydride blend microspheres: novel carriers for the controlled release of macromolecular drugs

Abstract

Rigid injectable microspheres were prepared from polyanhydride blends comprising a soft, rapidly-degrading polymer, viz. poly(carboxyphenoxyvaleric acid) (PCPV) and a rigid, slow-degrading polymer, viz. poly(carboxyphenoxyhexane) (PCPH). The incorporation of the soft polymer led to the formation of more dense microspheres. In the release environment, the soft polymer in the blend microspheres degraded more rapidly leaving behind a microporous structure consisting mostly of the slow-degrading polymer. PNP was released very quickly through these pores, and the rate was independent of blend composition. On the other hand release of lysozyme, a macromolecular solute, could be controlled by varying the blend composition. The influence of blending and technique of microsphere preparation on the morphology and release profile was also investigated.