FeSe₂-Decorated Bi₂Se₃ Nanosheets Fabricated svia 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.