A bifunctional S-doped Fe-N-C nanozyme with excellent oxidase-like activity and photothermal effect for tumor diagnosis and treatment

Tumors have become tremendous threatens to people's health. However, the development of high-performance theranostic materials, featuring with precise diagnosis and valid treatment, remains great challenges. Herein, S-doped FeNC (FeSNC) nanozyme was prepared by one-pot solvothermal method. The FeSNC exhibited outstanding oxidase-like activity due to the introduction of S. Density functional theory calculation demonstrated that S-doping could not only decrease the adsorption energy to O2 but also change the electron structure of Fe to accelerate the charge transfer between Fe and O, which resulted in the enhancement of the oxidase-like activity of FeSNC. Subsequently, folic acid was grafted on FeSNC for colorimetric detection of tumor cells based on the oxidase-like activity. Tumor cells could be discovered by naked-eyes resulted from the distinct color change. Furthermore, it exhibited excellent linear relationship in the range of 0-2000 and 2000-10000 tumor cells. On the other hand, under the irradiation of near-infrared light, FeSNC showed photothermal conversion performance due to the graphene-like structure of FeSNC, which was capable of killing tumor cells by photothermal therapy effectively. This study not only extends the synthesis method of high-performance nanozyme but also offers a promising strategy to design intelligent and simple platform for tumor diagnosis and treatment.