Palladium-triggered ratiometric probe reveals CO's cytoprotective effects in mitochondria

Carbon monoxide (CO) exposure causes mitochondrial dysfunction by targeting mitochondrial haem-protein cytochrome c oxidase. It may subsequently lead to cardiac dysfunction and long-term neurocognitive deficits. While other investigation suggests that the proper treatment of CO reduces cell death by reducing or preventing inflammatory and apoptosis. Therefore, it is urgent to evaluate its toxicity or safety by accurately quantifying CO content. Herein, we established a ratiometric fluorescent probe Mito-Ratio-CO to detect CO in mitochondria. Mito-Ratio-CO shows high selectivity and sensitivity to CO with a detection limit of 37.2 nM in the presence of palladium. After the evaluation of its cytotoxicity, Mito-Ratio-CO system was employed to determine exogenous and endogenous CO in HepG2 cells. Importantly, with this tool in hand, we were able to observe that endogenously produced CO arose when mitochondria suffered from oxidative stress.