Single Ho³⁺-Doped Upconversion Nanoparticles for High-Performance T ₂-Weighted Brain Tumor Diagnosis and MR/UCL/CT Multimodal Imaging

Multimodal bio-imaging has attracted great attention for early and accurate diagnosis of tumors, which, however, suffers from the intractable issues such as complicated multi-step syntheses for composite nanostructures and interferences among different modalities like fluorescence quenching by MRI contrast agents (e.g., magnetic iron oxide NPs). Herein, the first example of T ₂-weighted MR imaging of Ho³⁺-doped upconversion nanoparticles (UCNPs) is presented, which, very attractively, could also be simultaneously used for upconversion luminesence (UCL) and CT imaging, thus enabling high performance multi-modal MRI/UCL/CT imagings in single UCNPs. The new finding of T ₂-MRI contrast enhancement by integrated sensitizer (Yb³⁺) and activator (Ho³⁺) in UCNPs favors accurate MR diagnosis of brain tumor and provides a new strategy for acquiring T ₂-MRI/optical imaging without fluorescence quenching. Unlike other multi-phased composite nanostructures for multimodality imaging, this Ho³⁺-doped UCNPs are featured with simplicity of synthesis and highly efficient multimodal MRI/UCL/CT imaging without fluorescence quenching, thus simplify nanostructure and probe preparation and enable win-win multimodality imaging.