Double-activation of mitochondrial permeability transition pore opening via calcium overload and reactive oxygen species for cancer therapy

Abstract Background Calcium ions (Ca 2+ ) participates in various intracellular signal cascades and especially plays a key role in pathways relevant to cancer cells. Mitochondrial metabolism stimulated by calcium overload can trigger the opening of the mitochondrial permeability transition pore (MPTP), which leads to cancer cell death. Methods Herein, a mitochondrial pathway for tumour growth inhibition was built via the double-activation of MPTP channel. Fe 2+ doped covalent organic frameworks (COF) was synthesised and applied as template to grow CaCO 3 shell. Then O 2 was storaged into Fe 2+ doped COF, forming O 2 -FeCOF@CaCO 3 nanocomposite. After modification with folic acid (FA), O 2 -FeCOF@CaCO 3 @FA (OFCCF) can target breast cancer cells and realize PDT/Ca 2+ overload synergistic treatment. Results COF can induce the production of 1 O 2 under 650 nm irradiation for photodynamic therapy (PDT). Low pH and hypoxia in tumour microenvironment (TME) can activate the nanocomposite to release oxygen and Ca 2+ . The released O 2 can alleviate hypoxia in TME, thus enhancing the efficiency of COF-mediated PDT. Abundant Ca 2+ were released and accumulated in cancer cells, resulting in Ca 2+ overload. Notably, the reactive oxygen species (ROS) and Ca 2+ overload ensure the sustained opening of MPTP, which leads to the change of mitochondria transmembrane potential, the release of cytochrome c (Cyt c) and the activation of caspases 3 for cancer cell apoptosis. Conclusion This multifunctional nanosystem with TME responded abilities provided a novel strategy for innovative clinical cancer therapy. Graphical Abstract