Multifunctional Fluorescent Probes for Profiling Cys, Hcy, GSH, and SO₂: Illuminating Their Dynamics in Apoptosis and Ferroptosis

Abstract The ability to perform simultaneous fluorescence imaging of multiple targets is essential, providing crucial multi‐parametric information necessary for understanding complex biological interactions and processes. In this study, TBC , a novel multi‐signal fluorescent probe is presented, crafted for simultaneous differentiation and in situ real‐time monitoring of homocysteine (Hcy), cysteine (Cys), sulfur dioxide (SO 2 ), and glutathione (GSH), illuminating the dynamic metabolic status of endogenous reactive sulfur species. TBC achieves an ultrahigh signal‐to‐background ratio, enabling wash‐free direct fluorescence imaging of the dynamics and distribution of these entities in living cells and zebrafish. Notably, TBC has revealed distinctive dynamic metabolic features of Hcy/Cys/SO 2 /GSH during apoptosis and ferroptosis. This innovative probe acts as a key tool for unraveling the conversion networks of multiple reactive sulfur species and assessing the impact of metabolic oscillations during programmed cell death and the progression of diverse diseases, effectively uncovering concurrent biochemical dynamics in various biological settings and cell death events.