Visualization and Quantification of Base-Level SO₂ in Live Cells without Intracellular Background Interference Using Sensitive ¹⁹F-NMR

Sulfur dioxide (SO₂), as an endogenous gasotransmitter, is involved in a variety of physiological processes in living systems, however, distinction and quantification of base-level SO₂ in live cells pose great challenges for the current analytical techniques. We report an efficient way to visualize and quantify base-level SO₂ in different live mammalian cells by ¹⁹F-NMR. This method relies on a high-performance ¹⁹F-probe (<b>P1-CF</b>_<b>3</b>) that reacts with the reactive sulfur species (RSS) in the generation of distinct chemical shift profiles, which are well-resolved in the NMR spectrum. The quantitative reaction of the ¹⁹F-probe with SO₂ is fast and produces a stable addition product that is well distinguishable between the intra- and extracellular environment. The high performance of this method discloses that the base-level SO₂ in live cells varies greatly in different cell lines. The high accuracy and precision of RSS measurement by the reactive ¹⁹F NMR probe allow simultaneous quantification of base-level SO₂ in living cells and culture medium in real time without interference from other RSS and potential competitors and also without background signals.