Development of a new ratiometric probe with near-infrared fluorescence and a large Stokes shift for detection of gasotransmitter CO in living cells.

A near-infrared (NIR) ratiometric fluorescent probe, NIR-Ratio-CO, was developed for rapid detection of carbon monoxide (CO) in both solution and living cells through the strategy of Pd-mediated Tsuji-Trost reaction. This probe shows a rapid, highly specific and sensitive detection process for CO, accompanied by colorimetric and distinct ratiometric fluorescence changes at 655 and 592 nm with a large Stokes shift up to 195 nm. The detection limit for CO was measured to be about 61 nM by the fluorescence method. In addition, this probe was successfully applied for ratiometric imaging of both exogenous and endogenous CO in living cells, indicating that it can be used as a novel tool for ratiometric fluorescent detection of CO in living systems.