A Ratiometric Fluorescent Probe for Fast and Accurate Detection of Cysteine with Quantitative Fluorescence Models and its Application in Cell Imaging

Cysteine (Cys) concentration has important clinical significance as a biomarker of diseases. In this study, a cationic probe (probe T) was synthesized using benzothiazole as the fluorescent group and acrylate as the recognition site to Cys. Under an excitation wavelength of 360 nm, the fluorescence intensity decreased at 500 nm and the fluorescence intensity increased at 560 nm with the increase of Cys concentration, that is, the fluorescence spectrum deformation occurred. It was concluded that the fluorescence intensity ratio (I560 nm/I500 nm) of the probe T was linearly correlated with the Cys concentration. In addition, the probe T exhibited better selectivity for Cys compared to other biothiol, and the detection limit was calculated as 60.4 nM. Probe T was incubated with MCF-7 cells to enable fluorescence imaging of cells and co-localization of mitochondria and nuclei. This imaging technique could only achieve qualitative and semi-quantitative analysis, so precise quantitative analysis of Cys in the cell lysate was performed. The presence of background interference in the cell lysate could have led to biased quantitative results for Cys. The spectral shape deformation (SSD) was able to correct for background interferences affecting the spectral shape and intensity. By combining the SSD model with the proposed ratiometric fluorescence sensing method was able to accurately quantify Cys in cell lysates, and the accuracy was consistent with the results obtained from the kit. Therefore, this method will provide a new means for future research on Cys related diseases.