Electrochemical Biosensor Using DNA Embedded Phosphorothioate Modified RNA for Mercury Ion Determination

Mercury (Hg) and its compounds, originating from a variety of natural and anthropogenic sources, are ubiquitous in the natural environment, and cause severe environmental contamination and pose irreversible harm to human health. A fast and accurate sensing approach is of significant importance for mercury detection. Here, a label-free biosensor using Hg(II)-induced cleavage of phosphorothioate (PS) modified RNA was exploited. We designed a specific single-stranded DNA embedded with four PS-modified RNA (Hg-DPR) to improve the cleavage reaction yield, and then Hg-DPR was covalently linked with single-walled carbon nanotube field effect transistor (SWNTs/FET) via a peptide bond. The Hg-DPR can be efficiently cleaved after exposure to Hg(II), which further causes the conductivity of the SWNTs to change. Using the relative resistance change, the Hg-DPR/SWNTs/FET successfully detected Hg(II) levels as low as 10 pM, and the calibration curves were linear in the range of 50 pM to 100 nM and 100 nM to 10 μM. Additionally, Hg-DPR/SWNTs/FET exhibited excellent sensitivity, portability, and low-cost for Hg(II) detection.