A Simple and Highly Sensitive Mitochondrial Targeting Fluorescent Probe and Its Applications for the Detection of Intracellular Viscosity.

Viscosity is an important intracellular parameter which plays a significant role in cellular activities. Abnormal changes in viscosity could lead to inflammation and various types of diseases. Therefore, testing cellular microviscosity changes could help to develop new tools for disease diagnosis and treatment. To accurately monitor mitochondrial viscosity changes, a novel fluorescent probe called DWL-IY was developed by using the twisted intramolecular charge transfer (TICT) mechanism. The probe DWL-IY demonstrated high selectivity for viscosity and good photostability under both light and light-avoidance conditions. It also showed high sensitivity, with the fluorescence intensity increasing by 146-fold from methanol to glycerol and a large Stokes shift of 77 nm in methanol and 85 nm in glycerol. The positively charged DWL-IY molecule could be accurately colocalized in mitochondria and safely applied to Hela cells with low toxicity, responding sensitively to their mitochondrial viscosity variations.