Development of Salvianolic acid B-Tanshinone II A-Glycyrrhetinic acid compound liposomes: Formulation optimization and its effects on proliferation of hepatic stellate cells

The aim of this study was to systematically optimize and characterize the co-encapsulation process of Salvianolic acid B (Sal B), Tanshinone II A (TSN) and Glycyrrhetinic acid (GA) into liposomes. The liposomes (GTS-lip) were prepared using film hydration method combined with probe sonication to encapsulate two hydrophobic components (TSN and GA), and using pH gradient method to load hydrophilic component Sal B. The concentration of encapsulated drugs was measured by a reversed phase high performance liquid chromatography (RP-HPLC) method. Systematic optimization of encapsulation process was performed using single factor test, orthogonal test in combination with Box-Behnken Design. Optimum conditions are as follows: ratio of GA to lipid (w/w) = 0.08, ratio of Sal B to lipid (w/w) = 0.12 and pH of buffer = 3.3. Based on the conditions mentioned above, encapsulation efficiency of Sal B, TSN and GA reached target levels: (96.03 +/- 0.28)%, (80.63 +/- 0.91)% and (88.56 +/- 0.17)%, respectively. The GTS-lip had a unimodal size-distribution and a mean diameter of 191.3 +/- 6.31 nm. Morphology determination of the GTS-lip indicated that the liposomes were spherical, and there was no free drug crystal in the visual field of transmission electron microscopy. Also, the zeta potential of GTS-lip was detected to be -11.6 +/- 0.35 mV. In vitro release investigation of GTS-lip suggested that the release rate of GTS-lip significantly decreased compared to drug solution. The accumulative release percentage of TSN, GA and Sal B were 10% in 36 h, 4% in 36 h and 77% in 24 h. Meanwhile, GTS-lip exhibited definite activity on proliferative inhibition of hepatic stellate cells (HSC). GTS-lip decreased the viability of the HSC to higher than 75% at two high drug concentration groups in 24 h. At the same time, GTS-lip of two low drug concentration groups increased the inhibition rates by 2.3 folds and 1.9 folds separately at 48 h compared to 24 h. By contrast, inhibition activity of G-T-S solution group showed less change between 48 h and 24 h. The prolonged and enhanced activity in 48 h which GTS-lip group manifested might contribute to its sustained release effect. (C) 2014 Elsevier B.V. All rights reserved.