POLYANHYDRIDE MICROSPHERES .3. MORPHOLOGY AND CHARACTERIZATION OF SYSTEMS MADE BY SOLVENT REMOVAL

The morphological characterization of bioerodible polyanhydride microspheres is described. Microcapsules were prepared by solvent removal with different types of polymers. Polymers and microspheres were characterized by nuclear magnetic resonance spectroscopy (n.m.r.) X-ray powder diffraction, differential scanning calorimetry (d.s.c.) and scanning electron microscopy (SEM). Crystalline polymers like poly(sebacic anhydride) (P(SA)) tended to yield microspheres which had a crenellated and fractured surface, as judged by SEM. Polymers which had lower crystallinity, like carboxyphenoxypropane copolymerized with sebacic acid P(CPP-SA), yielded microspheres with smooth external surfaces and a porous core. Polymer crystallinity remained the same as the blank microspheres when a drug was dispersed as solid particles in the polymer. However, a decrease in polymer crystallinity was observed in cases where a drug formed a solution with the polymer. Understanding morphological and physical properties of these microspheres is essential for developing controllable delivery systems as well as for other applications. © 1990.