Structural and thermal properties of spray-dried methotrexate-loaded biodegradable microparticles

Drug–polymer interactions, structural properties, thermal behavior, and stability of biodegradable microparticles are fundamental aspects in the developing of new polymeric drug delivery systems. In this study, poly (d,l-lactide-co-glycolide) (PLGA) microparticles containing methotrexate (MTX) were successfully obtained by spray drying. Scanning electronic microscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction (XRD), and drug-loading efficiency were used to investigate the effect of drug–polymer ratio and its interactions, in a new MTX-loaded PLGA spray-dried microparticles. High levels of encapsulation efficiency (about 90 %) and a prevalent spherical shape were identified for different drug–polymer ratios used (9, 18, and 27 % m/m). The thermal analyses (DSC and TG) and XRD indicate that MTX is homogeneously distributed in the polymeric matrix, with a prevalent amorphous state in a stable molecular dispersion. Therefore, a correlation between drug content and the structural-thermal properties of drug-loaded PLGA microparticles was established using the thermal analysis data. The biodegradable microparticle leads to an increment of thermal stability of MTX, confirming that spray drying is an efficient process for obtaining MTX-loaded PLGA microparticles.