Near-Infrared Small Molecule as a Specific Fluorescent Probe for Ultrasensitive Recognition of Antiparallel Human Telomere G-Quadruplexes.

In the past 10 years, many fluorescent probes have been developed to recognize G-quadruplexes (G4s) since G4s play an important role in biological systems. However, the selectivity and sensitivity of existing probes for G4s limit their further applications. Herein, we design and synthesize a new probe (TOVJ) by introducing 9-vinyljulolidine into TO. The new probe exhibits almost no fluorescence in an aqueous solution. Upon interacting with G4s, especially the antiparallel G4s, the fluorescence intensity was greatly enhanced (maximum 2742-fold) with a large Stokes shift of 198 nm and the maximum emission peak at 694 nm (near-infrared region). TOVJ showed high sensitivity and selectivity to G4s over other DNA topologies (ssDNA/dsDNA), especially to antiparallel G4s. For antiparallel human telomere G4 detection, the limits of detection of Hum24 and 22AG Na were as low as 164 and 231 pM, respectively. This indicates that TOVJ is a highly sensitive fluorescence sensor that can be effectively used for antiparallel human telomere G4 detection. The result of live-cell imaging showed that TOVJ could enter live cells and locate in the mitochondria.