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Preparation and in Vitro Release of Silymarin Nanoparticles by Supercritical Anti-Solvent

??OBJECTIVE To enhance dissolution rate of silymarin (SM) by forming SM nanoparticles (SM-NA) with supercritical anti-solvent (SAS) method. MOTHODS Single-factor test was employed to investigate the influencing factors of particle size and yield of SM-NA, such as pressure, temperature, flow rate, and concentration of the solution. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to determine the state of SM-NA. The dissolution characteristics in vitro were investigated with 0.3% SDS aqueous solution as the solvent and compared with the SM powder. RESULTS Taking size distribution as well as yield of SM-NA as the evaluation indexes, the optimal prepration parameters were selected as followings:pressure 15 MPa, temperature 35 ??, flow rate 1.5 mL??min^-1, concentration 100 mg??mL^-1. The XRD and DSC of SM-NA described the decrease of SM in crystallinity, and it was transformed mostly with the amorphous state, compared with the SM powder. The accumalte release rate of SM-NA achieved 80% within 10 min, markedly higher than that of the SM powder and its commercial preparation. CONCLUSION The SM-NA prepared by SAS has remarkablly smaller particle size thus can greatly improve the in vitro release of SM.