Preparation and in vitro Evalution of Glycyrrhizic Acid Self-Assembled Micelles Loading Tanshinone ⅡA

  OBJECTIVE  Encapsulate tanshinone ⅡA (Tan ⅡA) in glycyrrhizic acid (GL) self-assembled micelles, to investigate the preparation process and characterization, and evaluate the anti-glioma cell activity in vitro.

  METHODS  Thin film dispersion method was used to prepare self-assembled micelles loaded with tanshinone ⅡA glycyrrhizic acid (TGM, Tan ⅡA-GL/Micelle). The particle size, polydispersity index (PDI) and Zeta potential of TGM were measured. The typical morphological characteristics of TGM were observed by transmission electron microscopy (TEM). HPLC was employed to determine the encapsulation rate of TGM, then the drug release of TGM under different pH conditions was investigated by dialysis bag method. The in vitro blood-brain barrier (BBB)-crossing ability of TGM was inspected by inverted fluorescence microscopy. Quantitative cell uptake experiment to investigate the specific mechanism of cell uptake. The cytotoxicity of free Tan ⅡA, GL and TGM on GL261 cells was investigated by MTT assay. The apoptotic effects of free Tan ⅡA, GL and TGM on GL261 cells were detected by flow cytometry.

  RESULTS  Thin film dispersion method was the best method to prepare self-assembled micelles loaded with tanshinone ⅡA glycyrrhizic acid. The particle size of TGM was about (121.87±5.85) nm, and the encapsulation efficiency of Tan ⅡA was (88.54±14.27)%, which was almost spherical in shape and the preparation was uniform and stable. TGM was capable of effective BBB-penetrating and the mechanism of uptake of self-assembled micelles by glioma cells was the uptake of preparations by clathrin-mediated endocytosis. TGM enhanced GL261 cell apoptosis from 12.28% (Free Tan ⅡA) and 13.32% (Free GL) to 31.16% (TGM), providing a promising potential to the GBM treatment.

  CONCLUSION  The TGM nano-micelles are self-assembled from GL and Tan IIA, which effectively overcomes low bioavailability and poor water solubility of Tan IIA. TGM can effectively cross the blood-brain barrier and be taken up by glioma cells through clathrin-mediated endocytosis, with good cytotoxicity and pro-apoptotic ability.