In Situ Lighting-Up Near-Infrared Metabolic Probes for Super-Resolution Imaging of Glycogen

High-fidelity tracking of glycogen dynamics in living biosystems is critical for exploring the biological role of glycogen metabolism in diseases. However, in situ information on the glycogen state mainly relies on a glucose uptake fluorescence probe 2-NBDG, which has proven to be extremely limited owing to the "always-on" fluorescence, short emission wavelength, and low signal-to-noise (S/N) ratio. Herein, we for the first time demonstrate a metabolic-activated off-on probe for glycogen through covalently attaching a molecular rotor with hydrophilic glucose at the C-2 position to guarantee good miscibility with a complete fluorescence-off state before metabolic incorporation into glycogen particles. The probe Glycogen-Red achieves negligible background fluorescence (1/30 times than 2-NBDG) and an ultrahigh S/N ratio (61-fold than 2-NBDG) of lighting-up near-infrared (NIR) fluorescence in glycogen biosynthesis. Notably, our probe has the unique characteristic of bypassing the washing steps, offering a powerful toolbox for real-time tracking of glycogen biosynthesis and super-resolution mapping of glycogen structures in living cells.