Trackable Mitochondria-Targeting Nanomicellar Loaded with Doxorubicin for Overcoming Drug Resistance

Multidrug resistance (MDR) has been recognized as a major obstacle to successful chemotherapy for cancer in the clinic. In recent years, more and more nanoscaled drug delivery systems (DDS) are constructed to modulate drug efflux protein (P-gp) and deliver chemotherapeutic drugs for overcoming MDR. Among them, d-α-tocopheryl polyethylene glycol succinate (TPGS) has been widely used as a drug carrier due to its capability of inhibiting overexpression of P-gp and good amphiphilicity favorable for improving permeation and long-circulation property of DDS. In the present work, a novel kind of mitochondria-targeting nanomicelles-based DDS is developed to integrate chemotherapeutics delivery with fluorescence imaging functionalities on a comprehensive nanoplatform. The mitochondria-targeting nanomicelles are prepared by self-assembly of triphenylphosphine (TPP)-modified TPGS and fluorescent carbon quantum dots (CQDs) in an n-hexane/H2O mixed solution, named CQDs-TPGS-TPP. Notably, although the drug loading content of doxorubicin (DOX) in the as-prepared nanomicelles is as low as 3.4%, the calculated resistant index (RI) is greatly decreased from 66.23 of free DOX to 7.16 of DOX-loaded nanomicelles while treating both parental MCF-7 cells and drug-resistant MCF-7/ADR cells. Compared with free DOX, the penetration efficiency of DOX-loaded nanomicelles in three-dimensional multicellular spheroids (MCs) of MCF-7/ADR is obviously increased. Moreover, the released DOX from the nanomicelles can cause much more damage to cells of drug-resistant MCs. These results demonstrate that our constructed mitochondria-targeting nanomicelles-based DDS have potential application in overcoming MDR of cancer cells as well as their MCs that mimic in vivo tumor tissues. The MDR-reversal mechanism of the DOX-loaded CQDs-TPGS-TPP nanomicelles is also discussed.