Preparation and evaluation of lyophilized liposome-encapsulated bufadienolides

OBJECTIVE: The objective of this study was to prepare bufadienolides-loaded liposome (BU-lipo). METHODS: The BU-lipo was prepared by a thin-film hydration method involving sonication and lyophilization procedures. The lyophilized BU-lipo was characterized with regard to the appearance and particle size by scanning electron microscopy, transmission electron microscopy, and photon correlation spectroscopy. The entrapment efficiency (EE) of BU-lipo was evaluated by the microdialysis technique. RESULTS: In the optimal formulation, Lipoid E-80 and the mass ratio of cholesterol to lipid were fixed at 1.25% and 0.05. The media diameters of BU-lipo before and after lyophilization were about 100 nm, and the EEs of bufalin (B), cinobufagin (C), and resibufogenin (R) were 86.5%, 90.0%, and 92.1%, respectively. In the EE study, the probe recoveries of B, C, and R were 21.53 +/- 1.14%, 19.49 +/- 1.34%, and 20.19 +/- 1.25%, respectively, at a flow rate of 4 microL/min by the gain method. The EE of BU-lipo evaluated by microdialysis and ultrafiltration were equivalent. CONCLUSION: The lyophilized BU-lipo contained trehalose (10%) was stable up to 6 months in a desiccator under 2 degrees C-8 degrees C. The microdialysis technique has a wide application perspective in the investigation of the free-drug concentration of microcarrier systems.