Photocaged fluorescent probes for spatiotemporally monitoring G-Quadruplex DNA in live cells.

G-quadruplexes (G4s) are important in biological processes such as gene transcription, telomere maintenance, and chromosome stability, and they hold promise as therapeutic targets in cancer research. Current G4 probes face challenges, including high background fluorescence, low regulation efficiency, and lack of spatiotemporal control. Photocaged technology offers precise temporal control and minimal background interference, making it a promising solution to these issues. Herein, we developed two photocaged G4 fluorescent probes, Nv-N-CQ and Nv-O-CQ, which use a photoremovable protecting group to block the fluorescence of coumarin-quinazoline (CQ) and its ability to bind to G4s. Upon UV light activation, Nv-O-CQ efficiently converted to CQ with minimal byproduct formation. It selectively bound to G4 structures, such as c-MYC, and enhanced their thermal stability. In cellular experiments, the probe demonstrated light-controlled fluorescence release and spatiotemporal specificity towards G4s in the cytoplasm. These findings highlight the potential of Nv-O-CQ for biological imaging, probe development, and spatiotemporal studies.