Rapid detection of CO in vitro and in vivo with a ratiometric probe showing near-infrared turn-on fluorescence, large Stokes shift, and high signal-to-noise ratio

A new near-infrared (NIR) fluorescent probe was developed for the detection of CO in living systems. This probe is based on a unique cyanine fluorophore and uses an allyl ether moiety as the reaction site. Optical studies in solution show that this probe has good water solubility and possesses desirable sensing properties for CO including rapid response, high selectivity and sensitivity, large Stokes shift (123 nm), distinct colorimetric changes, and significant turn-on NIR fluorescence changes at 715 nm with high signal-to-noise ratio. Ratiometric fluorescent detection of CO with this probe at 715 and 570 nm is also applicable. The sensing mechanism was proven to be a process of recovery of the fluorophore by removing the allyl group via Tsuji-Trost reaction. Furthermore, this probe was applied for detecting CO in living cells and animals with good bioimaging performance. Moreover, indicated by this probe, more CO could be produced under oxidative stress conditions. All the results indicate that this probe can be applied as a promising new tool for in vitro and in vivo detection of CO.