Double-Hemin G-Quadruplex Highly Sensitive Detection of Mercury Ions in Human Serum

The traditional G-quadruplex/hemin horseradish peroxidase has poor stability and a strong background signal and is not suitable for the detection of heavy metals such as mercury ions. In this work, we used the previous DNA strand for mercury ion detection and optimized it. Hemin is covalently bound to the 5′ and 3′ ends of the DNA strand. In the covalent binding state of double Hemin, the G-quadruplex has a strong catalytic activity and can catalyze the oxidation of hydrogen peroxide by ABTS. The formation of double chains with the addition of the S2 chain provides a rigid structure for detecting mercury ions. At the same time, after the addition of mercury ions, the formation of T-Hg2+-T structure further hinders the formation of G-quadruplex and reduces the absorbance value. The detection range in ultrapure water was 0–1000 nM, and the limit of detection concentration was 0.61 pM. In the human serum, the detection range is 0–300 nM and the LOD is 0.1 nM. In addition, the biosensor has excellent selective specificity and is expected to be used to detect mercury ions in organic biological environments and industrial environments contaminated by heavy metals.