Zinc oxide nanoparticles with catalase-like nanozyme activity and near-infrared light response:A combination of effective photodynamic therapy,autophagy,ferroptosis,and antitumor immunity

We prepared biocompatible and environment-friendly zinc oxide nanoparticles(ZnO NPs)with upconversion properties and catalase-like nanozyme activity.Photodynamic therapy(PDT)application is severely limited by the poor penetration of UV-Visible light and a hypoxic tumor environment.Here,we used ZnO NPs as a carrier for the photosensitizer chlorin e6(Ce6)to construct zinc oxide-chlorin e6 nanoparticles(ZnO-Ce6 NPs),simultaneously addressing both problems.In terms of penetration,ZnO NPs convert 808 nm near-infrared light into 401 nm visible light to excite Ce6,achieving deep-penetrating photodynamic therapy under long-wavelength light.Interestingly,the ability to emit short-wavelength light under long-wavelength light is usually observed in upconversion nanoparticles.As nanozymes,ZnO NPs can catalyze the decomposition of hydrogen peroxide in tumors,providing oxygen for photodynamic action and relieving hypoxia.The enhanced photodynamic action produces a large amount of reactive oxygen species,which overactivate autophagy and trigger immunogenic cell death(ICD),leading to antitumor immunotherapy.In addition,even in the absence of light,ZnO and ZnO-Ce6 NPs can induce ferroptosis of tumor cells and exert antitumor effects.