Gasotransmitters such as nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) are endogenously produced gaseous molecules which induce unique signalling responses in cellular systems. Among those gasotransmitters, NO plays vital roles in various physiological processes such as neurotransmission, platelet aggregation and adhesion, hormone secretion, vasodilatation, and immune response to infections.
Fluorescence probes for monitoring of nitric oxide (NO) is of great importance because this NO which is recognized as the first gasotransmitter plays the key roles in various physiological and pathological processes. Although a large number of fluorescence probes for NO have been developed so far, most of the ratiometric probes devised to date require a large synthetic effort. Because ratiometric fluorescence probes for detection of NO still remain rare but also they are based on fluorescence resonance energy transfer (FRET). In this study, ratiometric fluorescence probe monitoring of NO which is based on an excited-state intramolecular proton transfer (ESIPT) was developed.
Addition of NO to this probe leads to formation of a benzo[c]cinnoline derivative in association with a clearly observable dual-emission change in the blue and yellow regions. And this selective and simple probe shows better selectivity and sensitivity for NO than other relevant analytes such as RNS, ROS. Also, the value of this probe is further demonstrated by its use in the ratiometric detection of NO in the living cells.

References
1. Chen, L.; Wu, D.; Yoon, J*. Sensor Actuat B-Chem., 2018, 259, 347-353.
2. Chen, L.; Wu, D.*; Lim, C. S.; Kim, D.; Nam, S.-J.; Lee, W.; Kim, G.; Kim, H. M.*; Yoon, J*. Chem. Commun., 2017, 53, 4791-4794.