Dual-site functionalized NIR fluorescent material for a discriminative concentration-dependent response to SO2 in cells and mice.

Sulfur dioxide (SO2), as an important anti-oxidant and gaseous signaling molecule, plays fundamental roles in the regulation of intracellular signaling and cell death cellular bioenergetics. The accurate determination of the SO2 levels in an organism is a critical step in establishing its biological functions. Therefore, there is a high demand for developing efficient analytical methods for monitoring the wide range of concentration changes of SO2 in living systems. Herein, for the first time, we have successfully constructed a dual-site functionalized NIR fluorescent material (NIR-SP), which is capable of monitoring low concentrations of SO2 with red fluorescence responses and high concentrations of SO2 with blue fluorescence enhancements. Further studies absolutely confirmed that the discriminative response was due to the fact that the reactivity of the unsaturated C[double bond, length as m-dash]C double bond (site I) in NIR-SP was superior to that of the aldehyde group (site II). Furthermore, detection in a concentration-dependent manner was demonstrated by fluorescent imaging in cells and mice. We envision that this strategy would lead to insights into SO2 concentration-dependent biological effects and cell signals.