Despite the significant advantages of nano-micellar systems on drug delivery,the poor therapeutic outcome in clinic is ascribed to inefficient tumor uptake and poor intracellular drug release.Plumbagin(PBG),a natural naphthoquinone,displays potent antineoplastic activity toward human breast cancers,but poor delivery characters [1].Herein,a folate-receptor targeting redox-sensitive biodegradable micellar system composed on Pluronic F68-disulfide linkage-poly(lactic-co-glycolic acid)(F68-SS-PLGA)copolymer was formed for efficient breast tumor intracellular delivery of PBG [2].