Ratiometric fluorescence detection of Hg(II) in aqueous solutions at physiological pH and live cells with a chemosensor based on tyrosine

A fluorescent chemosensor (Pyr-Tyr) based on tyrosine showed highly selective and sensitive ratiometric response to Hg(II) among 14 metal ions in buffered aqueous solutions. The emission intensity ratio at 480 and 383 nm increased significantly from 0 to about 1.5 with the increase of Hg(II) concentrations (0–1 equiv.) and the ratiometric response to Hg(II) was not interfered by other metal ions such as Cu(II), Cd(II), and Ag(I). The detection limit of the chemosensor for Hg(II) was calculated to be 12 ± 1 nM (2.4 ppb). Pyr-Tyr exhibited ratiometric responses to Hg(II) in a wide range of pH values (pH 4.5–11.5) and the chemosensor was demonstrated to detect intracellular Hg(II) in HeLa cells. The binding mode of the chemosensor with Hg(II) was investigated by 1H NMR titration and pH titration experiments, and ESI mass spectrometry.