Highly sensitive surface acoustic wave biosensor for the detection of Hg 2+ based on the thymine-Hg 2+ -thymine structure.

The detection of mercury ions (Hg 2+ ) with an ultralow concentration is of great significance for the treatment of heavy metal pollution in industrial waste water and the monitoring of drinking water quality. In this study, a simple, sensitive, and portable surface acoustic wave (SAW) biosensor for the determination of Hg 2+ concentration was developed. First, a DNA fragment with a specific binding capacity for Hg 2+ was chemically adsorbed on to the sensitive region through forming Au-S bonds with the SAW biosensor. The DNA probe could then form a thymine-Hg 2+ -thymine (T-Hg 2+ -T) complex with strong affinity for Hg 2+ after immersion in a test solution containing Hg 2+ , resulting in a significant change in the response frequency of the device. The linear detection range of the device was 10 pM to 1 nM, while the limit of detection (LOD) was as low as 6.3 pM. Furthermore, the SAW biosensor exhibited excellent selectivity to Hg 2+ compared with that of interfering ions, e.g. , Ag + , Ba 2+ , Cu 2+ , Zn 2+ , Mn 2+ , Fe 3+ , Ca 2+ , and Na + . The results provide a new strategy for the preparation of portable devices that can monitor toxic heavy metal ions with high sensitivity and selectivity.