A novel mitochondria-targeted rhodamine analogue for the detection of viscosity changes in living cells, zebra fish and living mice

Monitoring the intracellular viscosity changes is crucial for better understanding diffusion-controlled cellular processes. Herein, we synthesized a novel phenyl-substituted imidazole-fused rhodamine analogue RV-1 with a long absorption wavelength at 573 nm and a large Stokes shift of about 82 nm for monitoring the changes in cellular viscosity. The new probe RV-1 showed a very strong fluorescence emission at around 655 nm, with a 48.5-fold enhancement of fluorescence intensity from methanol to 99% glycerol. Significantly, the innovative probe RV-1 was successfully applied for the detection of viscosity changes not only in living cells, but also in zebra fish and living mice.