Mitochondria-targeted NIR fluorescent probe for sensing Hg²⁺/HSO₃^- and its intracellular applications

Mercury and sulfur dioxide (SO₂) are common pollutants in the ecological environment, which are important factors causing many diseases of organisms. The lack of appropriate analytical tools has limited the further understanding of the relationship between ionic mercury (Hg²⁺) and SO₂. Herein, a bifunctional fluorescent probe LJ was designed and explored to simultaneously detect Hg²⁺ and SO₂ via desulfurization reaction and Michael addition reaction, respectively. Probe LJ showed distinct fluorescence responses which a large near-infrared fluorescence enhancement towards Hg²⁺ at λ_em = 713 nm and a blue shift at λ_em = 450 nm towards SO₂ without any spectral cross interferences. To the best of our knowledge, this is the first fluorescent probe with dual fluorescent emission channels to detect Hg²⁺ and SO₂ with the detection limit of 187 nM and 354 nM, respectively. Moreover, cell fluorescent imaging experiments indicated that the probe was mitochondria targetable and provided evidence that SO₂ could be used as an antidote to attenuate the toxicity of Hg²⁺ in living cells.