Characterization of polyanhydride microsphere degradation by DSC

Microspheres (2.91 μm diameter) were formed from poly(fumaric-co-sebacic anhydride) (P(FASA)) using a phase inversion microencapsulation technique. Blank microspheres, protein-loaded microspheres, and raw polymer were degraded in water for varying lengths of time to determine how degradation affects morphology and crystallinity. The rate of degradation was subsequently characterized using differential scanning calorimetry (DSC) and step-scan alternating DSC (SSADSC). As evident by the changing melting peak ratios during degradation, the protein-loaded microspheres were found to degrade at a more rapid rate than both the blank microspheres and the raw polymer, respectively. This was most likely because the release of protein from the microsphere surface led to an increased surface area available for degradation of this surface-eroding polymer.