Liver-targeting Resibufogenin-loaded poly(lactic-co-glycolic acid)-d-α-tocopheryl polyethylene glycol 1000 succinate nanoparticles for liver cancer therapy

Abstract

Liver cancer remains a major problem around the world. Resibufogenin (RBG) is a major bioactive compound that was isolated from Chansu (also called toad venom or toad poison), which is a popular traditional Chinese medicine that is obtained from the skin secretions of giant toads. RBG has strong antitumor effects, but its poor aqueous solubility and its cardiotoxicity have limited its clinical use. The aim of this study was to formulate RBG-loaded poly(lactic-co-glycolic acid) (PLGA)-d-α-tocopheryl polyethylene glycol 1000 succinate nanoparticle (RPTN) to enhance the treatment of liver cancer. RPTN, RBG-loaded PLGA nanoparticle (RPN), and RBG/coumarin-6-loaded PLGA-d-α-tocopheryl polyethylene glycol 1000 succinate nanoparticle (RCPTN) were prepared. The cellular uptake of RCPTN by HepG2 and HCa-F cells was analyzed using confocal laser scanning microscopy. Apoptosis was induced in HepG2 cells by RPTN, RBG solution (RS), and 5-fluorouracil solution (used as the negative controls), as assayed using flow cytometry. LD₅₀ (median lethal dose) values were determined for RS and RPTN, and the liver-targeting properties were determined for RCPTN in intravenously injected mice. A pharmacokinetic study was conducted in rats, and the in vivo therapeutic effects of RPTN, RPN, and RS were examined in a mouse tumor model. The results showed that RCPTN simultaneously delivered both coumarin-6 and RBG into HepG2 and HCa-F cells. The ratio of apoptotic cells was increased in the RPTN group. The LD₅₀ for RPTN was 2.02-fold higher than the value for RS. Compared to RS, RPTN and RPN both showed a significant difference in vivo not only in the pharmacodynamic study but also in anticancer efficacy, and RPTN performed much better than RPN. The detection indexes for drug concentration and fluorescence inversion microscopy images both demonstrated that RCPTN was much better at targeting the liver than RS. The liver-targeting RPTN, which displayed enhanced pharmacological effects and decreased toxicity for the loaded drug RBG, is therefore a promising intravenous dosage form that may be useful in the treatment of liver cancer.

Keywords:

• Resibufogenin
• PLGA-TPGS
• nanoparticles
• liver cancer
• HepG2 cells
• HCa-F cells

Acknowledgments

This work was supported by the Natural Science Foundation of Liaoning Province, People’s Republic of China (No. 2015020308) and the National Natural Science Foundation of China (No. 81473334), Distinguished Professor of Liaoning Province, Liaoning BaiQianWan Talents Program, Outstanding Youth Science and Technology Talents of Dalian (2014J11JH132 and 2015J12JH201), and the Innovation Team of Dalian Medical University. The authors are also grateful for material support provided by Dr Lin Mei, who works at Tsinghua University.

Disclosure

The authors report no conflicts of interest in this work.