Simultaneous Detection of Carbon Monoxide and Viscosity Changes in Cells

A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells. Carbon monoxide (CO) is produced in mammals and regulates many critical cellular functions, including the response to disease. A ruthenium(II) vinyl probe is presented that allows rapid, selective and sensitive detection of endogenous CO in live mammalian cells under normoxic and hypoxic conditions. By exploiting fluorescence lifetime imaging microscopy, the probe can also measure microscopic viscosity in live cells at the same time.