A metal-free near-infrared fluorescent probe for tracking the glucose-induced fluctuations of carbon monoxide in living cells and zebrafish

In this work, by taking full advantage of the transformation of nitro group into amino moiety under the direct reduction of CO, a new metal-free colorimetric and near-infrared fluorescent probe NIR-CO for rapid and specific tracing of intracellular CO has been constructed, and it also become the first reaction-based near-infrared fluorescent probe for CO detection without additional reagents. Probe NIR-CO could quantitatively detect CO at the nanomolar level and the detection limit was calculated as low as 6.1 nM. Additionally, probe NIR-CO with preeminent sensing properties was successfully applied to monitor the fluctuations of endogenous CO levels in living systems. In particular, the up-regulation of heme oxygenase-1 (HO-1) caused by transient glucose deprivation (TGD) in living cells and the down-regulation of HO-1 inhibited by high glucose (HG) in zebrafish were confirmed for the first time via mapping the glucose-induced fluctuations of CO levels. Thus, we anticipate that probe NIR-CO not only can serve as a powerful tool to investigate the detailed biological functions of CO in the pathophysiological processes, but also possesses potential applications of in situ monitoring HO-1 activity in the complex biological systems.