Optimization and Evaluation of Monodispersed Tetrandrine-Loaded PLA Microspheres Prepared With A SPG Membrane Emulsification Technique

To improve pulmonary drug concentrations and to maximize the effectiveness and minimize the adverse side effects, uniformsized tetrandrine-loaded polylactide (PLA) microspheres with a suitable particle size for pulmonary inhalation were prepared by the Shirasu Porous Glass (SPG) membrane emulsification technique. The main parameters influencing PLA microsphere properties were investigated: transmembrane pressure, circulation speed, high hydrophilic-lipophilic balance (HLB value), PLA concentration and oil-water volume ratio. Narrowly size-distributed tetrandrine-loaded PLA microspheres were obtained with a high drug encapsulation efficiency of 81.0% and an average diameter of 3.16 μm under optimized conditions. The results of Fourier transform infrared, differential scanning calorimetry and powder X-ray diffraction revealed that tetrandrine would be either molecularly dispersed in the polymer or distributed in an amorphous form. Further, the in vitro drug release experiment confirmed that the uniform-sized tetrandrine-loaded PLA microspheres showed suppressed burst release. These studies provide a basis for the use of uniformly sized 3.16 μm tetrandrine-loaded PLA microspheres for pulmonary inhalation.