Singlet Oxygen Generation in Dark‐Hypoxia by Catalytic Microenvironment‐Tailored Nanoreactors for NIR‐II Fluorescence‐Monitored Chemodynamic Therapy.

Singlet oxygen (1O2) has a potent anticancer effect, but photosensitized generation of 1O2 is inhibited by tumor hypoxia and limited light penetration depth. Despite the potential of chemodynamic therapy (CDT) to circumvent these issues by exploration of 1O2‐producing catalysts, engineering efficient CDT agents is still a formidable challenge since most catalysts require specific pH to function and become inactivated upon chelation by glutathione (GSH). Herein, we present a catalytic microenvironment‐tailored nanoreactor (CMTN), constructed by encapsulating MoO42− catalyst and alkaline sodium carbonate within liposomes, which offers a favorable pH condition for MoO42−‐catalyzed generation of 1O2 from H2O2 and protects MoO42− from GSH chelation owing to the impermeability of liposomal lipid membrane to ions and GSH. H2O2 and 1O2 can freely cross the liposomal membrane, allowing CMTN with a built‐in NIR‐II ratiometric fluorescent 1O2 sensor to achieve monitored tumor CDT. [ABSTRACT FROM AUTHOR]