Microstructural characterization of polyanhydride blends for controlled drug delivery

This research examines the microstructure of polyanhydride blends for use in drug delivery devices. Atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) studies were performed on the homopolymers and blends of the polyanhydrides poly(1,6-carboxyphenoxy hexane) (CPH) and poly(sebacic anhydride) (SA). AFM of the CPH/SA blends 20:80, 50:50, and 80:20 showed distinct patterns indicating spinodal decomposition and phase separation on the micron-scale. Because it has been shown that incorporated drugs will thermodynamically partition into phase-separated domains depending on their hydrophobicity, polyanhydride blends will be able to encapsulate larger bioactive compounds including nucleotides, proteins, and vaccines. Preliminary SAXS studies of the CPH/SA blend systems provide information on the crystalline morphology of the polymer. A peak shift to a lower q from poly(SA) to the blends indicates that the poly(CPH) is incorporated into and causes swelling of the interlamellar amorphous regions of poly(SA).