A novel ratiometric fluorescent probe for the detection and imaging of cysteine in living cells

Cysteine is an essential amino acid for humans and can be generated from the conversion of methionine or the interconversions with cystine. The detection of cysteine in the living system is of great importance for the diagnosis of related diseases. Based on the classical cysteine response mechanism, the sulfhydryl group of cysteine undergoes Michael addition with the acrylate to rapidly respond to form a seven-membered ring that specifically recognizes cysteine. In the present work, we designed a novel ratiometric fluorescent probe N-1, which contained the benzo[cd]indol fluorophore and the response group acrylate. As the concentration of cysteine increased, the fluorescence of I485 was significantly enhanced while the fluorescence intensity at 635 nm was weakened. Moreover, probe N-1 showed excellent sensitivity and selectivity to Cys with the calculated LOD of 4.0 × 10-9 M. Probe N-1 was successfully used for imaging cysteine in the living Hela cells with low cytotoxicity, indicating that this ratiometric fluorescent probe would be a novel and useful tool to monitor cysteine in the physiological or pathological processes.