Activatable 19F MRI Nanoprobes for Visualization of Biological Targets in Living Subjects

Visualization of biological targets such as crucial cells and biomolecules in living subjects is critical for the studies of important biological processes. Though 1 H magnetic resonance imaging (MRI) has demonstrated its power in offering detailed anatomical and pathological information, its capacity for in vivo tracking of biological targets is limited by the high biological background of 1 H. 19 F distinguishes itself from its competitors as an exceptional complement to 1 H in MRI through its high sensitivity, low biological background, and broad chemical shift range. The specificity and sensitivity of 19 F MRI can be further boosted with activatable nanoprobes. The advantages of 19 F MRI with activatable nanoprobes enable in vivo detection and imaging at the cellular or even molecular level in deep tissues, rendering this technique appealing as a potential solution for visualization of biological targets in living subjects. Here, recent progress over the past decades on activatable 19 F MRI nanoprobes made from three major 19 F-containing compounds, as well as present challenges and potential opportunities, are summarized to provide a panoramic prospective for the people who are interested in this emerging and exciting field.