New selective and sensitive fluorescence probes have always been in great demand for carbon monoxide, an important gasotransmitter molecule, which is involved in critical physiological and pathophysiological processes in the mammalian cardiovascular system. In this work, we synthesized a new palladacycle compound as a fluorescence turn-on probe for selective and quantitative detection of carbon monoxide. The weakly fluorescent probe quickly and selectively reacts with carbon monoxide and releases a highly fluorescent benzimidazole moiety, due to protonolysis of the palladacycle, which greatly enhances the fluorescence intensity. The selective reaction was against interference from other possible coexisting reactive oxygen species, and achieved a detection limit of ∼0.06 μM. Furthermore, the fluorescence turn-on probe was demonstrated with a high cellular uptake rate and was successfully applied for cell imaging of carbon monoxide in living cells.
Keywords: benzimidazole; carbon monoxide; cell imaging; endogenous CO; fluorescent probe; palladacycle.