A novel cysteine-specific fluorescent probe and its applications in biological imaging and food detection

The fluctuation of cysteine (Cys) levels in living organisms can serve as an important indicator for early diagnosis and warning of various diseases. Excessive dietary intake of Cys-rich foods may also have potential health impacts. Therefore, it is crucial to develop methods to detect Cys in both organisms and food samples. Due to the structural similarities among biological thiol molecules, it is challenging to develop probes that can distinguish Cys from other biothiols. In this study, we designed and synthesized a novel fluorescent probe MI-Cys with a maleimide group for the specific detection of Cys. The response mechanism of the probe MI-Cys for Cys is the intramolecular cyclization amidation triggered by the Michael addition of Cys. The probe MI-Cys exhibits a good linear relationship for low-concentration Cys (0-1.0 μM) and has been applied in cellular imaging and food detection. This study not only offers an alternative recognition mechanism for constructing highly specific Cys fluorescent probes, but also provides a new approach for future bioimaging applications and food safety.