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

Intracellular viscosity is an essential microenvironmental parameter and HS 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 HS 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 HS. Herein, a dual-response fluorescent probe (Mito-VS) is designed and synthesized to monitor the level of viscosity and HS, 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 HS, the probe can react with HS 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 HS concentration on the green channel in mitochondria. Most importantly, the probe is capable of studying the cross-talk influence of viscosity and HS in mitochondria, which is very beneficial for knowing the pathogenesis of AD.