A novel multi-functional fluorescent probe for dual-channel detection of SO2 and Hg2+ and dynamic visualization of SO2 fluctuations in vivo upon mercury exposure

Abstract

Although there are many drugs used for the treatment of mercury poisoning, it is remains confused that pathological symptoms associated with Hg²⁺-induced oxidative stress. It is reported that SO₂ can be generated as the anti-oxidant, and plays an important role in maintaining redox balance in cells. There has not yet been a study to precisely track the changes in SO₂ during mercury ion poisoning. We developed a novel dual-response fluorescence probe (CY-SPH) for respective or successive determination of Hg²⁺ and SO₂ in neutral aqueous media. The nucleophilic addition of HSO₃^- toward CY-SPH caused a significant fluorescence enhancement at 455 nm while the Hg²⁺ -triggered desulfurization of CY-SPH to the final phenolic product (CY-OH) elicited a markedly enhanced emission at 760 nm, allowing for two-color visualization of Hg²⁺ and SO₂ with good selectivity (detection limit: 67.2 nM for Hg²⁺ and 34.7 nM for SO₂). Moreover, CY-OH could undergo further nucleophilic addition reaction with HSO₃^- and resulted in a decrease in emission at 760 nm and an increase in emission at 438 nm, enabling the ratiometric determination of SO₂ with better sensitivity (detection limit, 3.50 nM). Significantly, CY-SPH can monitor the endogenous SO₂ fluctuations upon mercury exposure by means of confocal fluorescence imaging, which may prove valuable for deciphering the relationship between SO₂ levels and the mercury induced oxidative stress. We anticipated that this research will promote to understand the functions of SO₂ under the oxidative stress by Hg²⁺.

Keywords: Dual-channel; Hg(2+); Imaging; Multi-functional fluorescent probe; SO(2).