 Abstract osteosarcoma is the most common malignant tumor in the skeletal system with high mortality. Fytic acid, PA, a natural compound extracted from plant seeds, has shown some anti-tumor activity and good bone targeting ability. We have developed a novel pheronostics for magnetic resonance imaging, MI, and targeting therapy of osteosarcoma using fytic acid modified manganese dioxide nanoparticles, MnO2, at PA-NPs. These NPs are oligomers consisting of molecules attached to MnO2NPs, which have been characterized as amorphous structures. In vitro experiments showed that these NPs were able to be taken up by tumor cells, and when exposed to hydrogen peroxide in an acid environment, they produced manganese ions and oxygen, resulting in both MI and therapeutic effects against osteosarcoma. In vivo studies confirmed that the NPs accumulated in tumors and released their active components, leading to improved MI contrast and increased cytotoxicity. This article was authored by Qianju, Ronghuang, Ruemin Hu, and others.