Mitochondria- and nucleus-targeted fluorescent probe for chemometrics-enhanced detection of cysteine

The detection and imaging of cysteine (Cys) are vital for clinical applications, given its critical role as a biomarker in various diseases. In this study, a cationic fluorescent probe (probe T) was synthesized, featuring benzothiazole as a fluorescent group and acrylate as a Cys recognition site. Compared to other biothiols, probe T specifically detects Cys while targeting mitochondria and nuclei. In addition, probe T has low cytotoxicity and successfully imaged mitochondria and nuclei in MCF-7 cells. The fluorescence intensity ratio (F_{560 nm}/F_{500 nm}) of probe T was linearly correlated with the Cys concentration under 360 nm excitation, and the limit of detection was 60.4 nM. When quantifying Cys in complex biological samples, background interferences often lead to biased quantitative results. To mitigate this, chemometric method based on spectral shape deformation (SSD) theory was used to correct the spectral shape and intensity changes caused by background signals. By combining the SSD model with the ratiometric fluorescence sensing method, it was able to accurately quantify Cys in cell lysate, and the quantitative results were consistent with the kit. Therefore, this method not only provides a new diagnostic tool for the study of Cys-related diseases, but also provides an effective solution for background interference correction.