Yb/Er/Ho-engineered rare earth fluoride nanoparticles to unlock multimodal in vivo medical imaging

Fluorescence imaging with advanced multi-channel observation, high sensitivity, and high spatio-temporal resolution holds great promise for biomedical applications. However, the different absorption and scattering spectra of complex tissue structures present significant challenges for real-time investigations of live biological and physiological processes. Herein, we present Yb/Er/Ho-engineered rare earth fluoride nanoparticles with integrated multimodal imaging functions that can provide synergistic effects over any modality alone. The engineered nanoparticles can realize efficient and accurate diagnoses in clinical research. Employing Yb³⁺ sensitizers and both Er³⁺ and Ho³⁺ emitters, NaGdF₄:15%Yb,15%Er,x%Ho nanoparticles absorb an excitation wavelength of 980 nm and emit luminescence centered at 1525 nm and 1155 nm in the second near-infrared (NIR-II) window. In addition, upconversion emission in the visible region is also observed for multiplex signals. T₁- and T₂-weighted magnetic resonance (MR) imaging is achieved owing to the presence of paramagnetic Gd³⁺ and Ho³⁺ species. The high X-ray attenuation ability of the elemental constituents permits the use of the prepared nanoparticles as high-contrast X-ray computed tomography (CT) imaging agents. Taken together, this study shows the construction of an alternative multimodal nanoprobe with synergistic T₁- and T₂-MR/CT/downconversion luminescence (DCL) imaging abilities, which can provide an alternative approach for in vivo disease diagnosis and supervision.