Thermal properties and morphology changes in degradation process of poly(L-lactide-co-glycolide) matrices with risperidone

Determining thermal properties and morphology seems to be useful in the analysis of release and degradation processes form polymeric materials. Risperidone is available in the formulation of a long-acting injection based on poly(D,L-lactide-co-glycolide). Currently, alternative solutions are also offered, i.e., nano- and microparticles or implants, including copolymers of lactide and glycolide. The effect of risperidone content on the properties of poly(L-lactide-co-glycolide) matrices was determined. The study also involved an assessment of the changes during degradation. Risperidone free matrices and the matrices with risperidone were obtained by solvent casting. Thermal characteristics were tested by means of differential scanning calorimetry, and the morphology was evaluated using a scanning electron microscope. Risperidone did not change significantly semi-crystalline structure of poly(L-lactide-co-glycolide) matrices. The decrease in crystallization temperature and glass transition temperature during degradation was observed. Many pores and their deformation, the widening of pore area, cracks and slits because of degradation were observed. The analysis of thermal properties and morphology allowed us to explain degradation process. Matrices exhibited stable process of degradation, which may be advantageous for development of prolonged risperidone release systems.