A fluorescent probe for the specific detection of cysteine in human serum samples

Serum cysteine (Cys) level is correlated with many diseases. Therefore, it is very important to detect the concentration of serum cysteine with high sensitivity and accuracy. In this study, a turn-on fluorescent and colorimetric probe, (E)-2-(2-(4-formylstyryl)-4H-chromen-4-ylidene)malononitrile, termed as probe 1, was designed and synthesized for the detection of Cys in serum. Upon the addition of Cys, a remarkable enhancement in the fluorescence feature at 440 nm and a significant colour change of the probe solution were observed. Under optimal conditions, the probe enables quantitative analysis of Cys with high sensitivity. Moreover, the detection limit of Cys was calculated as 63 nM. The results showed that the fluorescence response of probe 1 to cysteine was highly selective when homocysteine (Hcy), glutathione (GSH) and other natural amino acids coexisted with cysteine under physiological conditions. Furthermore, the probe 1 could be used to accurately and sensitively detect cysteine in human serum.