An NIR Fluorescence Turn‐on and MRl Bimodal Probe for Concurrent Real‐time in vivo Sensing and Labeling of β‐Galactosidase

Abstract To realize sensing and labeling biomarkers is quite challenging in terms of designing multimodal imaging probes. In this study, we developed a novel β ‐galactosidase ( β ‐gal) activated bimodal imaging probe that combines near‐infrared (NIR) fluorescence and magnetic resonance imaging (MRI) to enable real‐time visualization of activity in living organisms. Upon β ‐gal activation, Gal‐Cy‐Gd‐1 exhibits a remarkable 42‐fold increase in NIR fluorescence intensity at 717 nm, allowing covalent labeling of adjacent target enzymes or proteins and avoiding molecular escape to promote probe accumulation at the tumor site. This fluorescence reaction enhances the longitudinal relaxivity by approximately 1.9 times, facilitating high‐resolution MRI. The unique features of Gal‐Cy‐Gd‐1 enable real‐time and precise visualization of β ‐gal activity in live tumor cells and mice. The probe's utilization aids in identifying in situ ovarian tumors, offering valuable assistance in the precise removal of tumor tissue during surgical procedures in mice. The fusion of NIR fluorescence and MRI activation through self‐immobilizing target enzymes or proteins provides a robust approach for visualizing β ‐gal activity. Moreover, this approach sets the groundwork for developing other activatable bimodal probes, allowing real‐time in vivo imaging of enzyme activity and localization.