Color-reversible fluorescence tracking for the dynamic interaction of SO₂ with Hg²⁺ in living cells

Mercury ion (Hg²⁺) is one of the most threatening substances to human health, and the mercury poisoning can damage physiological homeostasis severely in human, even cause death. Intriguingly, Sulfur dioxide (SO₂), a gas signal molecule in human, can specifically interact with Hg²⁺ for relieving mercury poisoning. However, the dynamic interaction of Hg²⁺ with SO₂ at the tempospatial level and the correlation between Hg²⁺ and SO₂ in the pathological process of mercury poisoning are still elusive. Herein, we rationally designed a reversible and dual color fluorescent probe (CCS) for dynamically visualizing Hg²⁺ and SO₂ and deciphering their interrelationship in mercury poisoning. CCS held good sensitivity, selectivity and reversibility to Hg²⁺ and SO₂, that enabled CCS to specifically detect SO₂ and Hg²⁺ via cyan fluorescence channel (centered around 485 nm) and red fluorescence channel (centered around 679 nm), respectively. Notably, the separate fluorescence signal changes of CCS realized the dynamic tracing of Hg²⁺ and SO₂ in living cells, and presented the potential for exploring the correlation between SO₂ and Hg²⁺ in mercury poisoning.