Tumor Microenvironment-Activated In Situ Synthesis of Peroxynitrite for Enhanced Chemodynamic Therapy.

Chemodynamic therapy (CDT) can induce cancer cell death through hydroxyl radicals (·OH) generated from Fenton or Fenton-like reactions. Compared with traditional therapies, CDT effectively overcomes inevitable drug resistance and exhibits low side effects. However, clinical application still faces challenges, primarily due to insufficient ·OH generation and the short-lifetime of ·OH in vivo. To address these challenges, we developed a peroxynitrite (ONOO - )-based CDT nanodrug (DOX@PMOF) composed of MOF-199, NO donor (PArg), and nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) activator (doxorubicin, DOX). In DOX@PMOF, MOF-199 serves as both a carrier for loading DOX and a source of Cu + for triggering CDT. Upon uptake by cancer cells, the high concentration of glutathione (GSH) reduces MOF-199 to Cu + , which then reacts with H 2 O 2 to generate ·OH. Moreover, the released DOX upregulates NOX4 expression, leading to the elevated H 2 O 2 level and thereby promoting a high-efficiency Fenton-like reaction for sufficient ·OH generation. Subsequently, PArg generates abundant NO in response to the tumor microenvironment, leading to a cascade of NO and ·OH for the in situ synthesis of ONOO - . ONOO - is more toxic and has a longer lifetime and diffusion distance than ·OH, resulting in a more effective CDT treatment. To further enhance the in vivo therapeutic effect, we coated DOX@PMOF with a homologous cell membrane to form an active tumor-targeting nanodrug (DOX@MPMOF), which has demonstrated the ability to effectively inhibit tumor growth and metastasis while exhibiting good biosafety.