Amphiphilic irinotecan–melampomagnolide B conjugate nanoparticles for cancer chemotherapy

Melampomagnolide B (MMB) is a natural sesquiterpene lactone product structurally related to parthenolide (PTL). Although MMB has been widely used to treat various types of cancers, such as glioma, leukemia and colon cancer, the effective delivery of MMB to cancer cells remains a challenge. An amphiphilic drug–drug conjugate (ADDC) strategy has been proposed and developed as a promising drug self-delivery system for cancer therapy because of its simple preparation, carrier-free nature, and high therapeutic activity. Herein, we present a new ADDC, which is synthesized by linking the hydrophilic anticancer drug irinotecan (Ir) and the hydrophobic anticancer drug MMB through a carbonate bond. The obtained amphiphilic irinotecan–melampomagnolide B conjugate (Ir–C–MMB) can self-assemble in water into stable nanoparticles with an average diameter of around 122.1 nm. After cellular uptake, the carbonate bond between the hydrophilic drug and hydrophobic drug can be cleaved to release free Ir and MMB under acidic conditions, which exhibit a synergistic effect in tumor cells. MTT results reveal that the Ir–C–MMB nanoparticles can effectively inhibit proliferation of cancer cells. The apoptosis data indicate that the apoptosis rate of cells treated with Ir–C–MMB nanoparticles is about 50% within 24 h, which is much higher than that of free Ir or MMB. Our results suggest that this ADDC strategy could be used as a drug delivery platform for MMB and its derivatives, and that it offers effective synergistic therapeutic efficacy.