Characteristics and drug release of drug-loaded microparticles prepared with different solvents using electrospraying

Poly(lactic-co-glycolic acid) (PLGA) microparticles containing the drug Celecoxib (CEL) were prepared at 10% drug loading with electrospraying using the solvents acetone (ACE) and methanol (MeOH) at molar ratios 100:0, 90:10 and 75:25 (ACE:MeOH). The particles produced were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Drug release from the particle samples was studied for 20h in a PBS media containing 1.5% SLS. Particles were in the size range of 2-5µm with near-spherical geometry, and with smooth or grainy surfaces for particles prepared with ACE or binary solvents respectively. The grainy morphology observed with binary solvents is explained by the poorer solubility of PLGA in MeOH resulting in early precipitation during particle formation. The particles prepared with binary solvents were smaller than those prepared with single solvent partly due to a more compact conformation of PLGA. Although all particles were prepared with 10%CEL, XPS measurements showed that the CEL concentration on the surface was between 26 and 39%. The surface CEL concentration for particles prepared with binary solvents was 38-39% while it was 26% for those prepared in ACE. This big difference indicates a phase separation between PLGA and CEL in the binary solvents. The drug release study showed diffusion driven release with over 90% of the drug content released in the 20h of measurement. The particles prepared with ACE showed a gradual release while those prepared with binary solvents showed a much quicker release. This quicker release is explained by the grainy particle morphology and surface enrichment of CEL, and these particles were also shown to disintegrate during drug dissolution. Electrosprayed PLGA/CEL microparticles prepared from single and binary solvents exhibited different size and morphology as well as surface chemistry and drug release profile demonstrating the significant effects of solvents on the characteristics of these drug microparticles.