Single Ho3+-Doped Upconversion Nanoparticles for High-Performance T2-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 T2‐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 T2‐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 T2‐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. The first example of T2‐weighted MR imaging of the sensitizer (Yb3+) and activator (Ho3+) in UCNPs is presented. These could also be simultaneously used for UCL and CT imaging, thus enabling the high performance multimodal MRI/UCL/CT imaging in single UCNPs. Impressively, the remarkable T2‐MRI capability of the Ho3+‐doped UCNPs favors the accurate early diagnosis of brain tumors.