Targeted, Stimuli-Responsive, and Theranostic ¹⁹F Magnetic Resonance Imaging Probes

Unlike conventional ¹H magnetic resonance imaging (MRI), ¹⁹F MRI features unambiguous detection of fluorine spins due to negligible background signals. Therefore, it is considered a promising noninvasive and selective imaging method for the diagnosis of cancers and other diseases. For ¹⁹F MRI, fluorine-rich molecules such as perfluorocarbons (PFC) have been formulated into nanoemulsions and used as its tracer agent. Along with advancements in other types of nanoparticles as targeted theranostics and stimuli-triggered probes and combined with the advantages of ¹⁹F MRI, PFC nanoemulsions are being empowered with these additional functionalities and becoming a promising theranostic platform. In this Review, we provide an overview of fluorine-based materials for sensitive ¹⁹F MRI of biological and pathological conditions. In particular, we describe designs and applications of recently reported stimuli-responsive and theranostic ¹⁹F MRI probes. Finally, challenges and future perspectives regarding the further development of ¹⁹F MRI probes for their clinical applications are described.