Effects of crystalline microstructure on drug release behavior of poly(epsilon-caprolactone) microspheres

This study investigates the release behavior of papaverine from poly(epsilon-caprolactone) (PCL) microparticles prepared by the oil/water solvent evaporation method. Microparticles were characterized in terms of crystalline morphology, size, drug loading, and encapsulation efficiency by using differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and UV spectrometry. The release behavior of papaverine was governed by the microstructure of PCL microparticles, suggesting that the environment for diffusion changes according to processing conditions such as polymer solution concentration, thermal history, and polymer molecular weight. As the PCL solution concentration increased, the drug release behavior showed a more sustained pattern. This result indicates that the size of the PCL microparticles is a determining factor for drug release. And when higher PCL molecular weight is used for preparation of microparticles, it led to a rapid release. Furthermore, a more delayed pattern of drug release profile was obtained in the sample prepared with higher thermal treatment. These results suggest that the crystalline microstructure of PCL microparticles plays an important role in its drug release behavior.