Construction and bioimaging application of novel indole heptamethine cyanines containing functionalized tetrahydropyridine rings

IR780 as a commercially available dye with near-infrared emission has been extensively applied in fluorescent probes and bioimaging. In this work, to further intensify the optical behavior, a tetrahydropyridine ring was used to replace the cyclohexene ring at the center of IR780, forming a cyanine dye Cy-NH with near-infrared emission. Photophysical properties demonstrated that Cy-NH exhibits good optical performance. In particular, Cy-NH contains two functional reaction sites (e.g. Cl and NH sites on the tetrahydropyridine ring) and can be used to construct functional cyanine dyes. Investigation on imaging showed that these cyanines can be used as near-infrared fluorescent imaging agents in living cells and in vivo.