Rational construction of a NIR fluorescent probe for CO imaging in living cells and zebrafish

Carbon monoxide (CO) is a highly emitted atmospheric pollutant that can pose a serious health risk when its concentration is too high. However, endogenous CO plays an important role in maintaining human health. The development of tools capable of detecting CO in environmental samples and biological samples is therefore essential. Although CO fluorescent probes have been reported, their further applications are limited by factors such as low sensitivity and emission wavelength. Here, we have constructed a CO probe with simple structure, high sensitivity, good selectivity and near-infrared (NIR) emission characteristics. The probe uses the dicyanoisophorone derivative as fluorophore and connects allyl moiety as the reaction site. After the response, the intramolecular charge transfer (ICT) process turns on and releases strong near-infrared fluorescence at 675 nm. The linear range of fluorescence intensity of the probe for CO concentration is 1–10 μM and the detection limit is as low as 58 nM. The high sensitivity and NIR emission give the probe excellent imaging of cellular exogenous and endogenous CO. Moreover, the probe can also be used to image CO in zebrafish. There is reason to believe that the probe can be a powerful tool for detecting CO concentrations in environmental samples and for analyzing the biological role of CO in organisms.