Polyanhydride microspheres as drug carriers. II. Microencapsulation by solvent removal

A new method to prepare polyanhydride microspheres, namely via solvent removal, is presented. Polyanhydrides composed of the following diacids were used: sebacic acid (SA), bis(p‐carboxy‐phenoxy) propane (CPP), and dodecanedioic acid (DD). Polymers were characterized by infrared (IR) spectroscopy, X‐ray diffraction, viscosity, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Drug release was affected by polymer composition, physical properties of the microspheres, and type of drug. The potential for injectable microspheres (size range 1–300 μm) made of copolymer (CPP‐SA 50:50), as biodegradable polymer carriers for the controlled release of insulin in treating diabetes mellitus, was assessed. Both 5% and 10% w/w insulin‐loaded microspheres were prepared. The 10% loaded microspheres produced the best clinical response, demonstrating five days of urine glucose control and four days of serum glucose control in diabetic rats.