Visualization of Mitochondrial DNA G-Quadruplexes with Isaindigotone Derived Near-Infrared Fluorogenic Probe

Mitochondrial DNA G-quadruplexes (mtDNA G4s) play potential regulatory roles in mitochondrial functions. Fluorescent probes for imaging mtDNA G4s may provide useful information to unveil their regulating dynamics and functions. However, the existing probes for mtDNA G4s still exhibit short absorption and emission wavelengths and limited sensitivity. Here, we develop a new isaindigotone-derived near-infrared (NIR) fluorogenic probe for imaging mtDNA G4s in live cells and in vivo. Different fluorescent probes are engineered by conjugating the isaindigotone scaffold with varying electron-donating groups. It is shown that the probe ISAP using dimethylaminophenyl as the electron-donating group exhibits near-infrared absorption/emission and a high fluorescence activation fold in response to G4s. Molecular docking simulations reveal that ISAP binds to