Figure 1.

Schematic illustration of theranostic ZnO₂ NPs for MRI and enhanced oxidative stress-based cancer therapy. Upon endocytosis by tumor cells, ZnO₂ NPs undergo dissociation in response to mild acidic pH, causing the release of H₂O₂ and Zn²⁺. The exogenously released H₂O₂ and Zn²⁺, that can increase the production of mitochondrial O₂·^- and H₂O₂ by inhibiting the electron transport chain (ETC), act synergistically to promote cancer cell killing through the cooperation of endogenous and exogenous ROS. Moreover, Mn-doping via partial cation exchange imparts ZnO₂ NPs with pH-activated MRI contrast ability.