Preparation and characteristics of oridonin-loaded nanostructured lipid carriers as a controlled-release delivery system.

In order to improve drug entrapment efficiency and loading capacity, nanostructured lipid carriers consisting of solid lipid and liquid lipid as a new type of colloidal drug delivery system were prepared. The dispersions of oridonin-loaded solid lipid nanoparticles and nanostructured lipid carriers were successfully prepared by the emulsion-evaporation and low temperature-solidification technique using monostearin as the solid lipid, caprylic/capric triglycerides as the liquid lipid and oridonin as the model drug. Their physicochemical properties of oridonin-loaded nanostructured lipid carriers and release behaviours were investigated and compared with those of solid lipid nanoparticles. As a result, the mean particle size was approximately 200 nm with narrow polydispersity index lower than 0.4 for all developed formulations. Zeta potential values were in the range -35 mV approximately -50 mV, providing good physical stability of all formulations. The differential scanning calorimetry and X-ray diffraction analysis results demonstrated lipid nanoparticles exhibited crystal order disturbance and thus left more space to accommodate drug molecules. The improved drug entrapment efficiency and loading capacity were observed for nanostructured lipid carriers and they enhanced with increasing the caprylic/capric triglycerides content. In vitro drug release experiments exhibited biphasic drug release patterns with burst release initially and prolonged release afterwards. These results indicated that nanostructured lipid carriers could potentially be exploited as a delivery system with improved drug entrapment efficiency and controlled drug release.