Synthesis and anti-metastasis activities of norcantharidin-conjugated carboxymethyl chitosan as a novel drug delivery system

•Carboxymethyl chitosan (CMCS) combined covalently with norcantharidin (NCTD).•CMCS-NCTD possessed enhanced solubility and superior anti-metastasis effects.•CMCS-NCTD decreased systemic toxicity and prolonged survival time of the mice.•CMCS-NCTD may serve as a potential therapeutic candidate for metastatic cancers. Carboxymethyl chitosan (CMCS), a water-soluble derivative of chitosan possessing numerous enhanced physicochemical and biological properties, has emerged as a promising biopolymer carrier for new drug delivery. Norcantharidin (NCTD) is an effective anti-tumor compound with severe nephrotoxicity. In this study, norcantharidin-conjugated carboxymethyl chitosan (CMCS-NCTD) was synthesized to reduce systemic toxicity and improve anti-tumor efficiency of NCTD. Our results demonstrated that CMCS-NCTD could significantly inhibit migration of tumor cells both in vitro and in vivo in a dose-dependent manner (P