A highly selective ESIPT-based fluorescent probe for cysteine sensing and its bioimaging application in living cells.

A novel fluorescent probe, viz . PI-Cys, was developed on the basis of the excited state intramolecular proton transfer (ESIPT) mechanism for the detection of cysteine (Cys). It consists of an new ESIPT dye as the fluorophore, linked via a hydroxyl moiety to an acrylate group. The acrylate group acts as an ESIPT blocking agent as well as a functional recognition moiety. In the presence of Cys, the reaction of Cys with PI-Cys results in cleavage of the acrylate moiety from PI-Cys, thereby unleashing the ESIPT process and leading to about 20-fold enhancement of fluorescence. The probe exhibits high sensitivity and selectivity toward Cys over homocysteine and glutathione. Finally, the probe was successfully applied for fluorescence bioimaging of Cys in living cancer cells. [ABSTRACT FROM AUTHOR]