A Nile Red/BODIPY-based bimodal probe sensitive to changes in the micropolarity and microviscosity of the endoplasmic reticulum

We herein report a fluorescent bimodal probe (1) capable of determining ER viscosity and polarity changes using FLIM and fluorescence ratiometry, respectively; during ER stress caused by tunicamycin, the viscosity was increased from ca. 129.5 to 182.0 cP and the polarity of the ER (dielectric constant, ε) enhanced from 18.5 to 21.1.