A novel near-infrared probe with large Stokes shift for the detection of viscosity changes in living cells

Highlights: • The probe NV-1 is a novel NIR fluorescent probe with large Stokes shift for detection of viscosity changes. • The probe NV-1 is specifically localized in mitochondria. • The probe NV-1 is successfully employed to monitor viscosity changes in living cells, zebra fishes and living mice. The status of living cells can be reflected by the changes of intracellular viscosity. Small molecular fluorescent probes are robust tools for measuring viscosity changes in living cells. Therefore, we constructed a near-infrared viscosity sensitive probe ZF1, which had a large Stokes shift, in methanol the Stokes reached to 148 nm and in glycerol it reached to 126 nm in viscous media, a significant enhancement of fluorescence at around 740 nm was observed. The probe ZF1 exhibited an 18.43-fold increasement of fluorescence intensity in glycerol. Moreover, in living cells, the probe ZF1 was applicable to detection of the viscosity changes.