Fabrication, characterization, and controlled release of eprinomectin from injectable mesoporous PLGA microspheres

Abstract

Batches of mesoporous poly(lactide-co-glycolide) (PLGA) microspheres were fabricated via an O/W emulsion–solvent evaporation method. The obtained microspheres were detected with scanning electron microscopy (SEM, S-4800) to observe their surface morphology. On observation it was found that many macropores were distributed on the microsphere surfaces. Then, eprinomectin (EPR) was employed as a model drug and was encapsulated by these mesoporous microspheres. The distribution state of the EPR in the microspheres was investigated via X-ray diffraction and differential scanning calorimetry. The test results indicated that the EPR was distributed in the microspheres with an amorphous state. After re-dispersing the EPR-loaded microspheres in ultrapure water, an extended-release formulation of EPR was obtained. The formulation was administered to Japanese white rabbits by subcutaneous injection to monitor the blood concentration of EPR. Plasma concentration profiles showed that the C_max of EPR (38.80 ± 9.50 ng mL⁻¹) appeared on the 2^nd day after subcutaneous injection. During the next 40 days, the plasma concentration of EPR maintained a value of 30.0 ng mL⁻¹. In addition, the biocompatibility of the EPR-loaded mesoporous microspheres (EPM) was also investigated by a biological sectioning method. Photographs of the histological sections illustrated that the EPM did not trigger a serious stimulus response at the injection site. Thus, they could be used to affirm that the mesoporous microspheres have a promising application in controlling veterinary drugs for sustained release.