A 32 full factorial design was employed for microsphere formulation using the solvent evaporation technique. The influences of two independent variables, the polymer and surfactant concentrations, on dependent variables, such as drug loading (DL) and the encapsulation efficiency (EE), were statistically investigated using Design Expert Software. Microspheres were characterized using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrophotometry (FTIR), and X-ray diffraction (XRD) and were evaluated for their in vitro drug release and stability at accelerated conditions.
The statistical evaluation of the design showed quadratic and linear models as significant models for DL (R2: 0.9932) and EE (R2 0.9696). The sizes of particles ranged from 54.7 μm to 140 μm, and the particles were spherical in shape with coarse surfaces. The most significant factor was the polymer amount. FTIR and XRD studies confirmed the drug-polymer compatibility. In vitro release of MGL from polymeric microspheres was found to occur a slower rate of up to 10 h.
The developed poly-e-caprolactone-loaded MGL microspheres can be successfully formulated. These microspheres can provide a promising sustained release drug delivery system for the treatment of hyperglycaemia associated with type-2 diabetes mellitus.