Preparation And Evaluation Of Glycyrrhizic Acid Loaded F127/TPGS Mixed Nanomicelles

Glycyrrhizic acid（GL）is pentacyclic triterpenoid glycoside extracted from Radix glycyrrhizae.It is the main active ingredient of R.glycyrrhizae with multiple biological activities such as antioxidative,anti-inflammatory,hepatoprotective,and antiviral properties.However,GL is highly polar and easily aggregates in aqueous solution.After being dissolved in hot water,it will precipitate as a colloidal precipitate after cooling.Moreover,GL has very poor permeability in the gastrointestinal tract and is difficult to absorb orally,which limits its clinical application.In this study,GL loaded pluronic F127（F127）/polyethylene glycol 1000 vitamin E succinate（TPGS）mixed micelles were developed to increase its solubility and bioavailability.Furthermore,the dissolution in vitro,the intestinal absorption in vivo,pharmacokinetics,tissue distribution and the therapeutic effect on mouse atopic dermatitis were studied.GL-F127/TPGS-MMs were prepared by thin film dispersion method.The encapsulation efficiency and drug loading of MMs were used as evaluation indexes.The formulation and process,including the ratio of F127 to TPGS,the concentration of polymer and GL,hydration temperature and time,were optimized by the single factor experiment.The optimal formulation and process of MMs were as follows:TPGS 180 mg,F127 270 mg,GL 70 mg,hydration temperature 50℃and hydration time 3 h.The prepared GL-F127/TPGS-MMs were the light yellow liquid with good clarity.The particle size,polydispersity index,and zeta potential were（28.20±5.63）nm,0.20±0.06,and-（5.24±1.55）m V,respectively.The encapsulation efficiency and drug loading were（97.57±5.29）%and（13.13±0.71）%.The results of stability showed that the GL-F127/TPGS-MMs were stable within 10 days at 4℃.The GL-F127/TPGS-MMs was spherical in shape with uniform distribution by transmission electron microscopy.The results of XRD and DSC indicated that GL was encapsulated in the micelles with the amorphous structure.The results of dissolution showed that GL-F127/TPGS-MMs had a sustained release compared with GL solution.The single-pass perfusion model was established in rats to investigate the intestinal absorption characteristics of MMs with absorption rate constant（Ka）and apparent absorption coefficient（Papp）as evaluation indexes.The result showed that the absorption of GL in the jejunum segment was significantly higher than that in the ileum segment（P<0.05）.Compared with GL solution,GL-F127/TPGS-MMs had a significantly higher absorption rate in the intestinal segment.The pharmacokinetics and tissues distribution of GL-F127/TPGS-MMs in rats were studied in this study.The pharmacokinetics study showed a higher AUC_0-∞and C_max of glycyrrhetinic acid after oral administration of GL-F127/TPGS-MMs as compared to GL solution.The biodistribution study showed a significantly higher accumulation of glycyrrhetinic acid in the liver and lung after oral administration of GL-F127/TPGS-MMs as compared to GL solution.A model of atopic dermatitis was established in 6-8-week-old female BALB/c mice by applying 2,4-dinitrochlorobenzene（DNCB）.After oral administration for 14days,the levels of lg E,ear swelling degree,thymus index,spleen index and skin lesion thickness of mice in GL-F127/TPGS-MMs groups were significantly decreased（P<0.05 or 0.01）compared with the model group.The thickness of the epidermis and dermis was significantly reduced in the GL-F127/TPGS-MMs group compared with the model group according to the pathological changes of the skin lesions.Compared with the GL solution groups,the AD pathological changes of the mice in the GL-F127/TPGS-MMs high-dose group were significantly improved,and the levels of lg E,ear swelling degree,thymus index,spleen index and skin lesion thickness were significantly reduced.These results suggested that GL-F127/TPGS-MMs had a significant therapeutic effect on atopic dermatitis in mice.