Chemiluminescence assay for the sensitive detection of iodide based on extracting Hg2+ from a T–Hg2+–T complex

Abstract

A simple and sensitive chemiluminescence assay for iodide (I⁻) detection was reported, which was based on iodide extracting Hg²⁺ from DNA featuring a stem-loop structure containing T–Hg²⁺–T. Specifically, Hg²⁺ induced random coiled G-rich single-strand DNA to form a stem-loop structure containing T–Hg²⁺–T. Because the binding of Hg²⁺ and I⁻ is much stronger than that of Hg²⁺ and thymine (T), I⁻ could extract Hg²⁺ from the stem-loop structure, releasing the DNA, which then bound with K⁺ and transformed into a K⁺-stabilized G-quadruplex (with hemin as a cofactor), which catalyzed the H₂O₂-mediated oxidation of luminol. The produced chemiluminescence as a sensing signal was applied to sensitively and selectively detect iodide with a detection limit of 12 nM. This system exhibited the first DNAzyme-based iodide sensor. Finally, the sensor was successfully applied for iodide detection in real lake water samples.