A Retrievable and Highly Selective Fluorescent Probe for Monitoring Sulfide and Imaging in Living Cells

Abstract

A novel selective fluorescent chemosensor based on an 8-hydroxyquinoline-appended fluorescein derivative (<b>L1</b>) was synthesized and characterized. Once combined with Cu²⁺, it displayed high specificity for sulfide anion. Among the various anions, only sulfide anion induced the revival of fluoresecence of <b>L1</b>, which was quenched by Cu²⁺, resulting in “off–on”-type sensing of sulfide anion. What’s more, the sensor was retrievable to indicate sulfide anions with Cu²⁺, and S^2–, in turn, increased. With the addition of Cu²⁺, compound <b>L1</b> could give rise to a visible pink-to-yellow color change and green fluorescence quenching. The resulting yellow solution could change to pink and regenerate to green fluorescence immediately upon the addition of sulfide anion; however, no changes were observed in the presence of other anions, including CN^–, P₂O₇^4–, and other forms of sulfate, making compound <b>L1</b> an extremely selective and efficient sulfide chemosensor. The signal transduction occurs via reversible formation–separation of complex <b>L1</b>Cu and CuS. What’s more, the biological imaging study has demonstrated that the chemosensor can detect sulfur anions in biological systems at a relatively low concentration