Rational Design of a Reversible Fluorescent Probe for Sensing Sulfur Dioxide/Formaldehyde in Living Cells, Zebrafish, and Living Mice.

Living systems contain a diverse array of molecules and ions undergoing dynamic changes by a web of interacting chemical reactions. Sulfur dioxide (SO2) and formaldehyde (FA) can be generated endogenously in living organisms to maintain their homeostasis, but aberrant production of these species is implicated with some critical diseases. The dynamic interaction between SO2 and FA on the overall health and disease of living organisms remains challenging to elucidate owing to a dearth of methods for monitoring dynamic fluctuation of these transient species. Herein, we present the rational design, synthesis, and photophysical property studies of the probe (CaP), the first reversible fluorescent probe for investigating the dynamics changes of SO2 and FA. Importantly, the highly desirable attributes of the robust probe CaP (such as ultrafast response to SO2 in less than 5 s, swift restoration by FA in less than 1 min) make it possible to reversibly monitor the dynamic fluctuation of endogenous SO2 and FA in real-time in living cells for the first time. Moreover, we demonstrate the utility of this unique probe to detect the fluctuations of SO2 and FA in living zebrafish and murine species. This work provides a powerful chemical tool for monitoring the dynamic interaction of endogenous SO2 and FA, which will pave an avenue for interrogating the intersecting correlation between SO2 and FA in health and disease states.