Carrier free nano-assembled redox dual-responsive biotin-artesunate conjugate for enhanced tumor therapy

Artesunate (ART) exhibits anti-tumor activity, however, its clinical application has been hindered due to its insufficient tumor selectivity and undesired toxicity to normal tissues. To improve its tumor selectivity, ART was conjugated with biotin through disulfide bond to produce Bio-SS-ART. The Bio-SS-ART could self-assemble into spherical nanoparticles in aqueous solution with particles size of 158.6 nm. In vitro release studies revealed that Bio-SS-ART exhibited accelerated release in reductive environment and released much faster in PBS than in water in the presence of GSH or DTT. Moreover, Bio-SS-ART also showed quick release in oxidative environment. Cell uptake studies showed that the fluorescence intensity of Rhodamine B (RhB) loaded Bio-SS-ART NPs exhibited 3.92-fold enhancement compared to that of free RhB. The inhibition of biotin significantly reduced the cellular uptake of RhB loaded Bio-SS-ART NPs and 7-hydroxycoumarin-labeled biotin (Bio-7-Hy) in a concentration and time-dependent manner. Multiple endocytotic pathways were included in the internalization of the biotinylated prodrug and nanomedicine. In vitro studies showed that the cytotoxicities of Bio-SS-ART and Bio-SS-ART NPs were 11.85-fold and 3.81-fold of that of ART against biotin receptor positive MCF-7 cells. In addition, the introduction of disulfide bond in biotinylated ART prodrugs exhibited higher anticancer activity than that of alkyl chain conjugated prodrug. Therefore, the biotinylation and introduction of disulfide bond could enhance the tumor targeting and anticancer activity of ART. Our study might provide a new strategy in designing highly efficient intracellular drug delivery and controlled drug release for future cancer treatment.