A hemicyanine-based colorimetric and ratiometric fluorescent probe for selective detection of cysteine and bioimaging in living cell.

A new ratiometric fluorescent probe based on a hemicyanine dye was synthesized. Investigation on the response behavior towards amino acids showed that the probe had a capability of rapidly and selectively detecting cysteine over other biothiols such as glutathione and homocysteine with similar structure and reactivity, and it also displayed a high selectivity and rapid response. Moreover, the probe had good water solubility, which authorized it could be applied in fluorescent bioimaging. The laser confocal fluorescence images indicated that the probe could visualize the intracellular cysteine. This work suggested that it could be utilized as a fluorescent indicator to discriminate the endogenous cysteine in living cells.