A novel highly sensitive fluorescent probe for imaging endogenous CO

As an important gaseous signal molecule, carbon monoxide (CO) plays a major role in multiple physiological and pathological processes. Therefore, it is significantly meaningful to develop fluorescent probes with features such as in situ imaging to detect CO in biological samples. However, the reported CO fluorescent probes still suffer from low sensitivity, poor selectivity, and low water solubility. In particular, due to the very low concentration of CO in organisms, these probes must have high sensitivity to achieve the detection of CO. To address this problem, we constructed a CO fluorescence probe (HS-CO) with a reasonable design, which can greatly increase the rigid plane of the probe through spontaneous intramolecular cyclization after the reaction with CO. The substantial increase in the fluorescence quantum yield after the reaction enabled it to achieve a strong change in the fluorescence signal and exhibit high sensitivity for detecting CO (LOD = 4.5 nM). Importantly, probe HS-CO was successfully used to detect endogenous and exogenous CO in HeLa cells. In addition, probe HS-CO successfully detected CO in zebrafish. These results together identified the great potential of the probe as a tool for functional analysis of CO in organisms.