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

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.