Immunotherapy has become a promising cancer therapy, but only works for a subset of cancer patients. Immunogenic photodynamic therapy (PDT) can prime cancer immunotherapy to increase the response rates, but its efficacy is severely limited by tumor hypoxia. Here we report a nanoscale metal-organic framework, Fe-TBP, as a novel nanophotosensitizer to overcome tumor hypoxia and sensitize effective PDT, priming non-inflamed tumors for cancer immunotherapy. Fe-TBP was built from iron-oxo clusters and porphyrin ligands and sensitized PDT under both normoxic and hypoxic conditions. Fe-TBP mediated PDT significantly improved the efficacy of anti-programmed death-ligand 1 (α-PD-L1) treatment and elicited abscopal effects in a mouse model of colorectal cancer, resulting in >90% regression of tumors. Mechanistic studies revealed that Fe-TBP mediated PDT induced significant tumor infiltration of cytotoxic T cells.

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Selective delivery of photosensitizers to mitochondria of cancer cells can enhance the efficacy of photodynamic therapy (PDT). Though cationic Ru-based photosensitizers accumulate in mitochondria, they require excitation with less penetrating short-wavelength photons, limiting their application in PDT. We recently discovered X-ray based cancer therapy by nanoscale metal–organic frameworks (nMOFs) via enhancing radiotherapy (RT) and enabling radiodynamic therapy (RDT). Herein we report Hf-DBB-Ru as a mitochondria-targeted nMOF for RT-RDT. Constructed from Ru-based photosensitizers, the cationic framework exhibits strong mitochondria-targeting property. Upon X-ray irradiation, Hf-DBB-Ru efficiently generates hydroxyl radicals from the Hf6 SBUs and singlet oxygen from the DBB-Ru photosensitizers to lead to RT-RDT effects. Mitochondria-targeted RT-RDT depolarizes the mitochondrial membrane to initiate apoptosis of cancer cells, leading to significant regression of colorectal tumors in mouse models. Our work establishes an effective strategy to selectively target mitochondria with cationic nMOFs for enhanced cancer therapy via RT-RDT with low doses of deeply penetrating X-rays.

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We report here the synthesis of a robust and porous metal-organic framework (MOF), Zr-TPDC, constructed from triphenyldicarboxylic acid (HTPDC) and an unprecedented Zr secondary building unit (SBU): Zr(μ-O)(μ-OH)(μ-OH). The Zr-SBU can be viewed as an inorganic node dimerized from two commonly observed Zr clusters via six μ-OH groups. The metalation of Zr-TPDC SBUs with CoCl followed by treatment with NaBEtH afforded a highly active and reusable solid Zr-TPDC-Co catalyst for the hydrogenation of nitroarenes, nitriles, and isocyanides to corresponding amines with excellent activity and selectivity. This work highlights the opportunity in designing novel MOF-supported single-site solid catalysts by tuning the electronic and steric properties of the SBUs.