An isothiocyanate-functionalized self-immolative near-infrared fluorescence probe for cysteine sensing and bioimaging in living systems

Biothiols play vital roles in human pathophysiology, with cysteine (Cys) a promising clinical biomarker for many diseases. Therefore, new tools to sensitively and specifically monitor Cys under physiological conditions and in living systems are urgently required. Consisting of a hemicyanine dye and isothiocyanate as the recognition group and self-immolative trigger, here we constructed a near-infrared (NIR) fluorescence probe named CyOH-NCS to specifically sense Cys. The hydroxyl-protected molecule maintained inactive fluorescence until specific attack of the isothiocyanate group by Cys to induce self-immolation and release of the native fluorophore as a NIR fluorescence output. Moreover, the CyOH-NCS probe was used to successfully visualize Cys in living cells, zebrafish and mice. Finally, hydrogen sulfide (H2S) release experiments demonstrated that the CyOH-NCS probe was a responsive H2S donor, indicating potential dual use in pathophysiological applications.

Automated summary

Biothiols, particularly cysteine (Cys), play crucial roles in human pathophysiology and have significant potential as clinical biomarkers for various diseases. In this study, a near-infrared (NIR) fluorescence probe named CyOH-NCS was developed to specifically detect Cys in physiological conditions and living systems. The probe showed excellent performance in visualizing Cys in living cells, zebrafish, and mice. Additionally, the probe exhibited responsive hydrogen sulfide (H2S) release, suggesting its potential dual application in pathophysiological studies.