Mitochondrial G-quadruplex targeting probe with near-infrared fluorescence emission

A novel thiazole orange based fluorescent probe NCT has been reported with promising G-quadruplex targeting ability. Interacting with G-quadruplexes will enhance its fluorescence intensity, but cause no obvious change in the CD spectrum. NCT exhibits high sensitivity and selectivity towards G4 over single strand DNA and double strand DNA. The viscosity-dependent fluorescence spectra and the excited-state lifetime experiment demonstrate that the restriction of the single bond between vinyl and quinolone group may be responsible for the 'turn-on" of the fluorescence. Moreover, NCT is used as a special dye for imaging G4 selectively under both UV irradiation and NIR irradiation in electrophoresis gel experiment, while commercially available dye Gel-Red can only stain DNA under UV irradiation. The mitochondria co-localization experiment, the high-resolution cellular imaging and the DNase digestion experiment have jointly proved that NCT is a potential probe for imaging G4 in mitochondria of living cells with excellent cell membrane permeability.