A novel “turn-on” fluorescent probe with a large stokes shift for homocysteine and cysteine: Performance in living cells and zebrafish

Carbazole-based fluorescent probes have a significant edge on structure and optical properties, but stokes shift of them were mostly less than 100 nm. In this work, a novel carbazole-based fluorescent probe, which featured with a large stokes shift (128 nm), was used to effectively detect homocysteine (Hcy) and cysteine (Cys). This probe revealed obvious color variation and a “turn-on” alteration of fluoresence toward Hcy and Cys. Furthermore, the probe works under physiological conditions and can image thiol in living cells as well as zebrafish because of its wonderful cell permeability. Notably, it provides a possibility to detect endogenous bio-thiols quantitatively in living cells.