Oxygen-Evolving Radiotherapy-Radiodynamic Therapy Synergized with NO Gas Therapy by Cerium-Based Rare-Earth Metal-Porphyrin Framework.

The efficacy of traditional radiotherapy (RT) has been severely limited by its significant side effects, as well as tumor hypoxia. Here, the nanoscale cerium (Ce)-based metaloxo clusters (Ce(IV) 6 )-porphyrin (meso-tetra (4-carboxyphenyl) porphyrin, TCPP) framework loaded with L-arginine (LA) (denoted as LA@Ce(IV) 6 -TCPP) is developed to serve as a multifarious radio enhancer to heighten X-ray absorption and energy transfer accompanied by O 2 /NO generation for hypoxia-improved RT-radiodynamic therapy (RDT) and gas therapy. Within tumor cells, LA@Ce(IV) 6 -TCPP will first react with endogenous H 2 O 2 and inducible NO synthase (iNOS) to produce O 2 and NO to respectively increase the oxygen supply and reduce oxygen consumption, thus alleviating tumor hypoxia. Then upon X-ray irradiation, LA@Ce(IV) 6 -TCPP can significantly enhance hydroxyl radical (•OH) generation from Ce(IV) 6 metaloxo clusters for RT and synchronously facilitate singlet oxygen ( 1 O 2 ) generation from adjacently-coordinated TCPP for RDT. Moreover, both the •OH and 1 O 2 can further react with NO to generate more toxic peroxynitrite anions (ONOO - ) to inhibit tumor growth for gas therapy. Benefitting from the alleviation of tumor hypoxia and intensified RT-RDT synergized with gas therapy, LA@Ce(IV) 6 -TCPP elicited superior anticancer outcomes. This work provides an effective RT strategy by using low doses of X-rays to intensify tumor suppression yet reduce systemic toxicity.