The optimal process conditions for preparing icariin nanosuspension(ICA-NS) and lyophilized powder were determined to initially investigate their stability and characterize the prepared nanosuspension. The anti-solvent precipitation-high shear method was used in the experiment, and the particle size(size), polydispersity index(PDI), and sedimentation ratio(H_0/H) were used as indicators to determine the optimal process conditions of ICA-NS by single-factor test method. Lyophilized powder of nanosuspension was prepared by freeze-drying method, and its crystalline morphology was observed by transmission electron microscope. The equilibrium solubility of icariin, nanosuspension and lyophilized powder was determined by shake flask method and their stability was initially investigated. The crystal structure of nano-lyophilized powder was characterized by differential scanning calorimetry(DSC) and X-ray powder diffraction(XRD). Finally, the dissolution in vitro of nano-lyophilized powder was determined by the small cup method to prepare the ideal icariin nanoparticles. Soy lecithin(SPC) was used as the main stabilizer and povidone was used as the steric stabilizer. The prepared ICA-NS was nearly round in shape, uniform in size, and stable at room temperature. The average particle size was(62.51±7.11) nm. The drug loading was 16% and the solubility was 50 times higher than that of the original drug. Drugs in suspension and lyophilized powder were dispersed in nanoparticles in an amorphous state. The in vitro dissolution experiments showed that the cumulative release rate of nano-lyophilized powder reached 100% at 10 min, indicating that the dissolution rate of lyophilized powder was significantly increased after preparing into nano-lyophilized powder. Preparation of ICA-NS lyophilized powder by antisolvent precipitation-high shear method is simple, easy to operate, and can significantly improve its water solubility. However, the process conditions have some influence on its stability, which needs further study.
Keywords: characterization; icariin; lyophilized powder; nanosuspension; preparation.