A Rapid "off-on" copper-induced AIE active sensor for fluorimetric detection of cysteine

As a sulfur-containing amino acid, cysteine (Cys) plays a crucial role in life process. Abnormal Cys content can trigger a series of diseases, such as developmental delay, hair discoloration, neurological diseases and cardiovascular diseases. In this work, 4-(10-{4-[Bis-(4-hexyloxy-phenyl)-amino]-phenyl}-anthracen-9-ylethynyl)-benzoic acid (FSD-103) was found to exhibit the aggregation-induced emission (ME) property and a further fluorescence quench with a high selectivity to Cu2+ in 1 min. Then, due to the strong interaction between Cys and Cu2+, the combination of FSD-103 and Cu2+ was influenced, which restored the AIE effect. Therefore, based on the FSD-103-Cu2+ system, a new "off-on" fluorescence sensor for Cys detection was realized in 8 min, where a linear relationship between the fluorescence intensity and Cys was found in both low concentration range (1-10 mu M) and high concentration range (10-17 mu M), and the detection limit was 0.2 mu M. Interestingly, by soaking a filter paper, the visualization of the fluorescence recovery effect of Cys can be easily realized at the mu M level. This method shows acceptable selectivity, which provides a practicable method for the application of organic molecules in Cys detection.