Celastrol self-stabilized nanoparticles for effective treatment of melanoma

Abstract

Background: Celastrol (CEL), a triterpene extracted from the Chinese herb tripterygium wilfordii, has been reported to have profound anticancer activities. However, poor water solubility and high side toxicities have severely restricted the clinical applications of CEL. Purpose: We proposed a facile “in situ drug conjugation-induced self-assembly” strategy to prepare CEL-loaded nanoparticles (CEL-NPs) that exhibited enhanced antitumor activity against melanoma. Methods: First, the CEL was chemically conjugated onto a methoxyl poly(ethylene glycol)-b-poly(L-lysine) (mPEG-PLL) backbone, resulting in the conversion of the double hydrophilic mPEG-PLL polymer into an amphiphilic polymer prodrug, mPEG-PLL/CEL. The obtained mPEG-PLL/CEL could self-assemble into stable micelles in aqueous solution due to the hydrophobic association of CEL moieties in the side chains and the possible electrostatic interaction between the carboxyl group in CEL and the residue amine group in the PLL segment. Thus, the obtained mPEG-PLL/CEL nanoparticles were named CEL self-stabilized nanoparticles (CEL-NPs), which were then characterized by dynamic light scattering and transmission electron microscopy. Furthermore, the antitumor effects of the CEL-NPs were investigated by an MTT assay in vitro and in a B16F10 tumor-bearing mice model. Results: The CEL-NPs exhibited sustained drug release behavior and were effectively endocytosed by B16F10 cells. Furthermore, the in vivo antitumor evaluation demonstrated that the CEL-NPs had remarkably higher tumor growth inhibition rates and lower systemic side effects than free CEL. Conclusion: In summary, our present work not only demonstrates the generation of stable CEL-loaded nanoparticles for the efficient treatment of melanoma but also describes a general way to prepare drug self-stabilized nanomedicine for anticancer therapy.