A red-emitting fluorescent probe for visualizing mitochondrial microviscosity by cell imaging

The visual detection of mitochondrial viscosity is of considerable significance in that it is associated with various cellular functions. Herein, a novel red-emitting viscosity probe YD-Mito constructed by linking phenylamine derivatives and benzo[e]indolium through a C–C double bond has been designed and synthesized. It was found that YD-Mito exhibited a special response to viscosity accompanying with a sharp fluorescence enhancement (20-fold) at 620 nm. Importantly, YD-Mito can precisely localized in mitochondria independent from membrane potential and visualized the mitochondrial viscosity. Therefore, probe YD-Mito could provide a powerful tool for the determination of mitochondrial viscosity.