FeSe2‐Decorated Bi2Se3 Nanosheets Fabricated via Cation Exchange for Chelator‐Free 64Cu‐Labeling and Multimodal Image‐Guided Photothermal‐Radiation Therapy

Multifunctional theranostic agents have become rather attractive to realize image‐guided combination cancer therapy. Herein, a novel method is developed to synthesize Bi2Se3 nanosheets decorated with mono‐dispersed FeSe2 nanoparticles (FeSe2/Bi2Se3) for tetra‐modal image‐guided combined photothermal and radiation tumor therapy. Interestingly, upon addition of Bi(NO3)3, pre‐made FeSe2 nanoparticles via cation exchange would be gradually converted into Bi2Se3 nanosheets, on which remaining FeSe2 nanoparticles are decorated. The yielded FeSe2/Bi2Se3 composite‐nanostructures are then modified with polyethylene glycol (PEG). Taking advantages of the high r 2 relaxivity of FeSe2, the X‐ray attenuation ability of Bi2Se3, the strong near‐infrared optical absorbance of the whole nanostructure, as well as the chelate‐free radiolabeling of 64Cu on FeSe2/Bi2Se3‐PEG, in vivo magnetic resonance/computer tomography/photoacoustic/position emission tomography multimodal imaging is carried out, revealing efficient tumor homing of FeSe2/Bi2Se3‐PEG after intravenous injection. Utilizing the intrinsic physical properties of FeSe2/Bi2Se3‐PEG, in vivo photothermal and radiation therapy to achieve synergistic tumor destruction is then realized, without causing obvious toxicity to the treated animals. This work presents a unique method to synthesize composite‐nanostructures with highly integrated functionalities, promising not only for nano‐biomedicine but also potentially for other different nanotechnology fields.