A novel near-infrared fluorescent probe for highly selective detection of cysteine and its application in living cells.

A novel red-emitting fluorescent probe (DDNA) for cysteine has been rationally designed and synthesized, which exhibited a low limit of detection to Cys (0.26 μM) as well as a favorable large stokes shift (λEm-λEx = 128 nm). This novel fluorophore (HDM), which features a large π-conjugation system and typical intramolecular charge transfer (ICT) process, has a long emission wavelength at 631 nm. Besides that, as a turn-on fluorescent probe, it shows high selectivity and sensitivity for Cys over other metal ions and amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). Finally, the probe DDNA was successfully applied to bioimage intracellular Cys in Hela cells with low cytotoxicity.