Multimodal Visualization of Bioorthogonal Systems by Off-On Luminescence and Enhanced Magnetic Resonance Imaging

Bioorthogonal chemistry is a rising field investigating chemical reactions in physiological environments with high specificity. However, only very few examples concern the real-time monitoring of bioorthogonal reactions by luminescence or magnetic relaxivity. To fill this gap, herein, the Eu(III)-based complex is reported as a small-molecule optical imaging agent which shows off-on luminescence and provides quantitative analysis for the progress of the bioorthogonal reaction. The characteristic signal is achieved through efficient energy harvesting and transferring to the Eu(III) from the expansion of the conjugated system of the antenna. Moreover, the gadolinium(III) counterpart significantly enhances relaxivity in magnetic resonance imaging (MRI) after the bioorthogonal reaction since the rotational correlation time is shortened with increased molecular sizes and weights.