A Novel Methacryloyl–Masked NIR Fluorescent Probe for Detection of Cysteine and Its Application in Bioimaging

Cysteine (Cys) detection is recognized as an essential element in this investigation due to the critical function of Cys in several physiological processes in living organisms. A new NIR fluorescent probe SNC-Cys has been synthesized by incorporating a five-membered malononitrile derivatized ring as an electron withdrawing group, and a methacryloyl group detection moiety for cysteine. After adding Cys, SNC-Cys shows an emission of 654 nm and further works as a "Turn-on" probe via ICT photomechanism. SNC-Cys has high sensitivity and selectivity for Cys (LOD = 0.46 µM) and can discriminate it from other closely related amino acids, molecules with structural similarity, and in some cases very close functional group likeness. Thus, these results allow the effective imaging of Cys in living A549 cells which indicates good cell permeability and high applicability in live cell imaging. This study anticipates that SNC-Cys could be an aid in the detection of Cys-relevant diseases.