A Dual-Response Fluorescent Probe for the Detection of Viscosity and H₂S and Its Application in Studying Their Cross-Talk Influence in Mitochondria

Intracellular viscosity is an essential microenvironmental parameter and H₂S is a critical gaseous signaling molecule, which are both related to various physiological processes. It is reported that the change of viscosity and an imbalance of H₂S production in the mitochondria are both associated with overexpression of amyloid betapeptide (Aβ), which is thought to play a central role in the pathogenesis of Alzheimer's disease (AD). However, to our best knowledge, no fluorescent probe is found for dual detection of mitochondrial viscosity and H₂S. Herein, a dual-response fluorescent probe (Mito-VS) is designed and synthesized to monitor the level of viscosity and H₂S, respectively. Mito-VS itself is nonfluorescent due to a free intramolecular rotation between dimethylaniline and pyridine. After the increase of viscosity, the rotation is prohibited and an intense red fluorescence is released. Upon the addition of H₂S, the probe can react with H₂S to form compound 3 and a strong green fluorescence can be observed. Moreover, the probe possesses a good mitochondrion-targeting ability and is applied for imaging the change of viscosity on the red channel and visualizing the variation of exogenous and endogenous H₂S concentration on the green channel in mitochondria. Most importantly, the probe is capable of studying the cross-talk influence of viscosity and H₂S in mitochondria, which is very beneficial for knowing the pathogenesis of AD.