A Novel Single-Molecule Fluorescence Lifetime Probe for Apoptosis Diagnosis Through Mitochondrial SO

As a key signaling molecule, sulfur dioxide (SO2) plays a crucial role in maintaining physiological homeostasis. In this work, we designed a mitochondria-targeted fluorescent probe (MIC) for independently detect SO2 (short-wavelength) and DNA (long-wavelength) in real time. It is worth noting that our research reveals a dual role of that SO2 in regulating oxidative stress. At appropriate levels, it acts as a modulator, whereas excessive amounts induce apoptosis by reducing mitochondrial membrane potential, upregulating p53/Bax, downregulating Bcl-2, and activating the caspase-3 cascade. The apoptotic process induces mitochondrial membrane permeability changes, triggering the release and nuclear translocation of the probe MIC, which subsequently emits red fluorescence. Using time-resolved fluorescence imaging technology, we further observed a significant increase in the average fluorescence lifetime of the DNA channel. This finding demonstrates that the MIC probe not only enables dual-channel monitoring of mitochondrial SO2 and nuclear DNA but also precisely evaluates the apoptotic process through changes in fluorescence lifetime. This innovative tool provides an important means for in-depth study of the SO2-mediated apoptotic mechanism and opens up new strategies for the diagnosis of mitochondrial-related diseases.