Degradation of an Aromatic Polyanhydride with Enhanced Thermal Properties.

Polyanhydrides have been studied as a drug delivery vehicles due to their surface-eroding behavior which results in zero-order release. However, many polyanhyrides have thermal and solubility properties that make them difficult to formulate for these applications. Poly[α,α'-bis(-carboxyphenoxy)--xylene] (CPX) is an aromatic polyanhydride that has thermal and solubility properties enabling facile processing. The polymer's degradation profile exhibited an induction period up to 10 days in which degradation product concentration in the media was minimal, followed by a period of stable release of the biocompatible degradation product. Scanning electron microscope images and molecular weight changes of the polymer matrices confirm that this polymer is primarily surface-eroding. The combination of thermal properties, solubility, polymer degradation time, and erosion mechanism indicate that poly(CPX) is be a suitable matrix candidate for extended, controlled drug delivery.