Preparation And Evaluation Of Glabridin Nanocrystal Gel

Objective Glabridin is well-known due to its skin whitening property, however the poor water solubility and stability restrain its dermal application. The aim of the present work was to enhance the penetration and stability of the glabridin by using the nanocrystal and gel technology. The glabridin nanocrystals gel formulation was optimized, in vitro and in vivo performance was evaluated systematically.Methods HPLC method for determination of glabridin content, and the standard curve was prepared, intra-and inter-day precise were also studied, the stability of the glabridin was investigated. Saturated solubility of glabridin was determined by using shake-flask method.Glabridin nanocrystals were prepared using anti-solvent precipitation-homogenization method, and Box-Behnken design was performed to investigate the effects of crucial formulation variables on particle size and to optimize the nanocrystals formulation. The particle size and polydispersity index was analyzed by a NICOMPTM 380 Submicron particle analyzer, and the morphology of nanocrystals was observed under TEM. The permeation of glabridin from suspensions was determined by using a vertical Franz diffusion cell. In vivo skin delivery studies were performed in rats, and the stability of glabridin nanocrystals were performed at room temperature for three months.The nanocrystals gel was prepared by adding the carbomer 934 P into the glabridin nanocrystals and then adjusting the pH to near neutral. The viscosity and rheological property of the gel were analyzed by the rheometer, and the morphology of nanocrystals gel was observed under TEM. The permeation of glabridin nanocrystals gel was determined by using a vertical Franz diffusion cell. Skin irritation test was studied by applying the nanocrystals gel on the rats skin for 7 days with 2 times a day, and then the pathological changes were observed by naked eyes and pathological section. For stability investigations, glabridin nanocrystals gel was studied by centrifuged for 30 min at the speed of 5000 rpm. Further more, the gel was stored at room temperature for three months to investigate the physical and chemical stability of glabridin.Results HPLC method for determining the content of glabridin shown a good specificity, which is not affected by other substrates, the retention time was shorter than 10 min. The concentration of glabridin in 90-720 ?g/mL exhibit a good linear relationship. The RSD of intraand inter-day value are less than 2% and 5%, respectively. Stability experiment investigation results showed that the glabridin was stable within 48 h; Eventually determine the method to determine glabridin set the minimum detection limit of 0.4 ?g/mL, the minimum quantitative limit of 1.0 ?g/mL, the recovery experiment results showed that RSD value is less than 2%, conform to the standard. The solubility of glabridin in water, ethanol, dioxane, acetone and dimethyl sulfoxide were 9.1×10-4, 702.26, 725.00, 710.01 and 430.79 mg/mL, respectively.The optimal formulation consisted of 0.25% glabridin, 0.47% Poloxamer 188 and 0.11% Polyvinylpyrrolidone K30, and the nanocrystals showed an average particle size of 149.2 nm with a polydispersity index of 0.254. Furthermore, the nanocrystals exhibited significantly enhanced drug permeation flux of glabridin through rat skin with no lag phase both in vitro and in vivo, compared to the coarse suspension and physical mixture. The glabridin nanocrystals showed no significant particle aggregates and a drug loss of 5.46% after storage for 3 months at room temperature.The viscosity of the nanocrystals gel was aroud 17.5 Pa·s, and the rheological property of the gel exhibited a pseudoplastic fluid property. The morphology of the nanocrystals gel was spherical which was consistent with the nanocrystals. In addition, the nanocrystals gel exhibited significantly enhanced drug permeation flux of glabridin through rat skin with no lag phase in vitro, compared to the coarse suspension and physical mixture. The glabridin nanocrystals gel showed no significant particle aggregates after 30 min centrifuge at 5000 rpm and a drug loss of 4.45% after storage for 3 months at room temperature.Conclusion The particle size and size distribution of the optimal glabridin nanocrystals were small and homogeneous. And the nanocrystals exhibited significantly enhanced drug permeation flux of glabridin through rat skin with no lag phase both in vitro and in vivo, compared to the coarse suspension and physical mixture. The stability of nanocrystals was preferable within 90 days. In addition, the viscosity of nanocrystals gel was sufficient to adhere to the skin. In addtion, the nanocrystals gel shown a good drug permeation behavior in vitro. There is no irritation after 7 days administration on rats skin.