An Ultrasensitive Gold Nanoband Aptasensor for Mercury(II) Detection in Aquatic Environment

Heavy metal contamination in aquatic environment has made great adverse impacts on human health and environment. In this work, a label-free electrochemical gold nanoband aptasensor (GNA) was developed using thymine-Hg2+-thymine (T-Hg2+-T) coordination chemistry for Hg2+ detection in drinking water. The gold nanoband sensor contains gold nanoband working electrode with a band thickness of 100 nm. The nanoscale working electrode increases the mass transfer rate and sensitivity for Hg2+ detection. Moreover, the gold nanoband sensors are cost-effective and can be easily regenerated by cutting the edge after the performance decreases dramatically compared with microelectrodes and disk electrodes. T-rich oligonucleotides modified with thiol group was self-assembled onto the working electrode through Au-S covalent bonding. In the presence of Hg2+, oligonucleotides will capture Hg2+, thus inducing the conformational change from single-strand to duplex-like structure that would promote electron transfer. Electrochemical impedance spectroscopy (EIS) was used to detect the Hg2+-mediated conformational changes. By optimizing experimental conditions, the linear range of proposed biosensor is from 0.1 nM to 1 μM, and the limit of detection is 40 pM (8 ppt). Furthermore, this nanobiosensors exhibited high selectivity and a great potential to detect trace Hg2+ in real samples from aquatic environment.