A real-time colorimetric and ratiometric fluorescent probe for rapid detection of SO2 derivatives in living cells based on a near-infrared benzopyrylium dye

A benzopyrylium-based dye, Probe 1, was developed as a near-infrared fluorescent probe for the detection of SO2 derivatives (sulfite/bisulfite) in pure aqueous solution. In the presence of sulfite/bisulfite, the solution of Probe 1 displayed significant changes in its absorption (from 650 nm to 420 nm) and emission (from 690 nm to 489 nm) spectra. Probe 1 exhibits excellent selectivity and high sensitivity toward sulfite/bisulfite and the detection limit (S/N = 3) for bisulfite is as low as 10.4 nM. Specifically, Probe 1 shows a fast response time (within 10 s) toward sulfite/bisulfite, which makes it capable for real-time sensing or imaging both in vitro and in vivo assays. Probe 2, an analogue of Probe 1, as a turn-on fluorescent probe was also developed and displayed similar properties for the detection of sulfite/bisulfite. The demonstration of Probe 1 as a ratiometric fluorescent probe and Probe 2 as a turn-on fluorescent probe for the detection of SO2 derivatives was achieved in living HeLa cells and A431 cells, respectively.