A Quinoline-Based Ratiometric and Reversible Fluorescent Probe for Cadmium Imaging in Living Cells

We report a novel ratiometric and reversible fluorescent probe for Cd(2+) detection utilizing a 6-(dimethylamino)quinaldine derivative as the fluorophore and a 2-hydrazinopyridine derivative as Cd(2+) chelator. This ratiometric fluorescent probe possesses favorable photophysical properties. It shows a large (55 nm) red-shift from 515 nm to 570 nm in the emission spectrum. Moreover, this probe also exhibits an excellent linear relationship of fluorescence intensity ratio (F570/F515) (R(2)=0.989) vs. Cd(2+) concentration in the range of 0-10 µM at physiological pH, which can serve as a "quantitative detecting" probe for Cd(2+). Utilizing this sensitive and selective probe, we have successfully detected Cd(2+) in living cells.