Preparation of poly(DL-lactide-co-glycolide) microspheres encapsulating all-trans retinoic acid

Poly(DL-lactide-co-glycolide) (PLGA) microspheres containing all-trans retinoic acid (atRA) were prepared by o/w solvent evaporation method and various preparation parameters, such as poly(vinyl alcohol) (PVA) concentration in aqueous solution, PVA MW, drug weight, solvent, polymer MW, and polymer weight, on the characteristics of microspheres and drug release were investigated. PVA concentration in water phase was a critical factor in making microspheres consistently with smooth surface and round shape. In our study, at least 2% (w/v) of PVA in aqueous solution was necessary for making microspheres with round shape. The particle size of microspheres ranged 10-100 microm. AtRA was slowly released from PLGA microspheres over 30 days. Sterilization of microspheres by ethylene oxide (EO) gas at 37 degrees C did not significantly affect the characteristics of drug release or its morphology. Cell growth inhibition of atRA was affected by preparation process of microspheres rather than the EO-gas sterilization process. These results indicate that PLGA microspheres containing atRA are acceptable for controlled release devices for use in the treatment of brain tumor.