mtDNA-Specific Ultrasensitive Near-Infrared Fluorescent Probe Enables the Differentiation of Healthy and Apoptotic Cells.

Mitochondrial DNA (mtDNA) as a class of important genetic material is easily damaged, which can result in a series of metabolic diseases, hereditary disease, and so on. mtDNA is an ultrasensitive indicator for the health of living cells due to the extremely short physiological response time of mtDNA toward damage (ca. 5.0 min). Therefore, the development of specific ultrasensitive fluorescent probes that can in real-time monitor mtDNA in vivo are of great value. With this research, we developed a near-infrared twisted intramolecular charge transfer (TICT) fluorescent probe . is a thread-like molecule with an A-π-D-π-A structure, based on the dicyanoisophorone fluorophore. The molecular design of enabled the specific binding with dsDNA (binding constant () = 8.5 × 10 M) within 1.3 min. And the appropriate water-oil amphiphilicity makes significantly accumulate in the mitochondria, enabling the specific binding to mtDNA. The fluorescence intensity at 640 nm of enhanced linearly with increasing concentrations of mtDNA. Dicyanoisophorone as the strong electron-withdrawing group that was introduced into both ends of the molecule resulted in being a classic quadrupole, so it could ultrasensitively detect trace mtDNA. The minimum detection limit was 71 ng/mL. Moreover, the large Stokes shift (λ = 435 nm, λ = 640 nm) makes suitable for "interference-free" imaging of mtDNA. Therefore, was used to monitor trace changes of mtDNA in living cells; more importantly, it could be used to evaluate the health of cells by monitoring microchanges of mtDNA, enabling the ultrasensitive evaluation of apoptosis.