Formulation and characterization of bufadienolides-loaded nanostructured lipid carriers

Objective: The aim of this study was to design bufadienolides-loaded nanostructured lipid carriers (BUNLCs) to reduce the degradation of drugs in rat plasma. Methods: BU-NLCs were prepared by a modified melt-emulsification ultrasonic technique and then characterized by particle size distribution, zeta potential, entrapment efficiency, differential scanning calorimetry, and X-ray diffraction. Results: The optimal formulation consisted of glyceryl monostearate 1.8%, medium-chain triglyceride 0.75%, oleic acid 0.45%, Lipoid E-80(R) 1.5%, Pluronic F68 1.0%, and sodium deoxycholate 0.25%. The particle size distribution and the range of zeta potential of BU-NLCs were 104.1 +/- 51.2 nm and -15 to -20 mV, respectively. The entrapment efficiencies of the bufadienolides were all above 85%. In the enzymolysis study, the chemical stability of cinobufagin (C) in BU-NLCs was enhanced by being encapsulated in particles of NLC and adjusting the pH of the surrounding environment to 7.0. The half-life of C was 17-fold longer than that in bufadienolides solution. The in vitro release showed that the release from BU-NLCs was slower than from bufadienolides solution and followed the Weibull equation. Differential scanning calorimetry and X-ray diffraction showed that BU-NLC was in an amorphous state after lyophilization. Conclusion: These results indicated that NLC could be developed as a carrier with improved drug plasma stability and offering controlled drug release.