Tumor Micro-Environment Sensitive 19F-Magnetic Resonance Imaging in Vivo

Abstract 19F MRI has been paid great attention because of its higher signal-to-noise ratio and larger chemical shift than 1H MRI. However, the low 19F content and sensitivity of environment limit its development in clinic. Herein, considering the large surface area and abundant metal active sites of metal organic framework (MOF) nanoparticles, we fabricated Zr-based MOF nanoparticles (UiO-66-F NPs) with an organic ligand of tetrafluoro-terephthalic acid (F4PTA) as a pH-sensitive 19F MRI contrast agent, which remained stable in a neutral condition, but could release free F4PTA in an acidic condition to enhance 19F MRI signal. As a proof of concept, UiO-66-F NPs-based contrast agent could turn on the 19F MRI signal in an acidic tumor micro-environment. The results provide an alternative strategy for the design of tumor micro-environment responsive 19F MRI contrast agents.