Highly Sensitive Cyanine Dyes for Rapid Sensing of NAD(P)H in Mitochondria and First-Instar Larvae of Drosophila melanogaster

We have developed two highly sensitive cyanine dyes, which we refer to as probes A and B. These dyes are capable of quick and sensitive sensing of NAD­(P)­H. The dyes were fabricated by connecting benzothiazolium and 2,3-dimethylnaphtho­[1,2-d]­thiazol-3-ium units to 3-quinolinium through a vinyl bond. In the absence of NAD­(P)­H, both probes have low fluorescence and absorption peaks at 370 and 400 nm, correspondingly. This is because of their two electron-withdrawing acceptor systems with high charge densities. However, when NAD­(P)H reduces the probes’ electron-withdrawing 3-quinolinium units to electron-donating 1,4-dihydroquinoline units, the probes absorb at 533 and 535 nm and fluoresce at 572 and 586 nm for A and B correspondingly. This creates well-defined donor–π–acceptor cyanine dyes. We successfully used probe A to monitor NAD­(P)­H levels in live cells during glycolysis, under hypoxic conditions induced by CoCl2 treatment and after treatment with cancer drugs, including cisplatin, camptothecin, and gemcitabine. Probe A was also employed to visualize NAD­(P)H in Drosophila melanogaster first-instar larvae. We observed an increase in NAD­(P)H levels in A549 cancer cells both under hypoxic conditions and after treatment with cancer drugs, including cisplatin, camptothecin, and gemcitabine.