Squaraines are extremely bright fluorophores that have never been reported as potential molecular rotors. Here, we report a red-emitting pyrrolyl squaraine molecular rotor. This rotor has been modified to target the plasma membrane of cells, allowing the measurement of viscosity variations at the cell surface as well as in intracellular vesicles by FLIM (Fluorescence Lifetime Imaging). Congratulations to Sonia Pfister, Halina Anton (UMR7021), and our partners at the IMAG’IC platform in Cochin (Paris) and all the authors for this collaborative work.
