Theranostic 2D ultrathin MnO₂ nanosheets with fast responsibility to endogenous tumor microenvironment and exogenous...

The fabrication of functional nanoparticles with unique ultra-sensitivity to endogenous tumor microenvironment (TME) is of great significance for their improved theranostic performance and easy excretion out of the body, which has not been realized among diverse nano-sized photothermal agents for photothermal therapy (PTT) of tumor. In this work, we report on the synthesis of 2D ultrathin MnO₂ nanosheets for highly efficient PTT against tumor with ultra-sensitivity to endogenous TME. These ultrathin 2D MnO₂ nanosheets show the intriguing characteristic of disintegration and releasing of Mn²⁺ in response to the mild acidic condition and elevated reducing microenvironment of TME, which has successfully realized the pH- and reducing-responsive T₁-weighted magnetic resonance imaging of tumor. Importantly, the high PTT efficiency of 2D MnO₂ nanosheets responsive to exogenous NIR irradiation has been systematically demonstrated both in vitro and in vivo for suppressing the tumor growth. This first report on the exploring of TME-sensitive photothermal agents with concurrent diagnostic and therapeutic (theranostic) functions significantly broadens the biomedical application of 2D functional biomaterials, which also promotes the further potential clinical translations of nano-sized photothermal agents.