A NaYbF ₄: Tm ³⁺ nanoprobe for CT and NIR-to-NIR fluorescent bimodal imaging

Early diagnosis that combines the high-resolutional CT and sensitive NIR-fluorescence bioimaging could provide more accurate information for cancerous tissues, which, however, remain a big challenge. Here we report a simple bimodal imaging platform based on PEGylated NaYbF ₄: Tm ³⁺ nanopaticles (NPs) of less than 20 nm in diameter for both CT and NIR-fluorescence bioimaging. The as-designed nanoprobes showed excellent in vitro and in vivo performances in the dual-bioimaging, very low cytotoxicity and no detectable tissue damge in one month. Remarkably, the Yb ³⁺ in the lattice of NaYbF ₄: Tm ³⁺ NPs functions not only as a promising CT contrast medium due to its high X-ray absorption coefficiency, but also an excellent sensitizer contributing to the strong NIR-fluorescent emissions for its large NIR absorption cross-section. In addition, these NPs could be easily excreted mainly via feces without detectable remnant in the animal bodies.