Nanoenabled Intracellular Calcium Bursting for Safe and Efficient Reversal of Drug Resistance in Tumor Cells.

Multidrug resistance (MDR) of a tumor is the main cause of failure of clinical chemotherapy. Herein, we report a simple, yet versatile, tumor-targeting "calcium ion nanogenerator" (TCaNG) to reverse drug resistance by inducing intracellular Ca2+ bursting. Consequently, the TCaNG could induce Ca2+ bursting in acidic lysosomes of tumor cells and then reverse drug resistance according to the following mechanisms: (i) Ca2+ specifically accumulates in mitochondria, suppressing cellular respiration and relieving tumor hypoxia, thus inhibiting P-glycoprotein biosynthesis by downregulating HIF-1α expression. (ii) Ca2+-bursting-induced respiratory depression blocks intracellular ATP production, which further leads to the P-gp incompetence. As a result, the TCaNG could decrease the IC50 of DOX to MCF-7/ADR cells by approximately 30 times and reduce the proliferation of drug-resistant tumors by approximately 13 times without obvious side effects. This simple, safe, and effective "Ca2+ bursting" strategy holds the potential for clinical application in tumor treatment.