Selective molecular interplay in electrochemical sensing: DNA-templated Hg(II) capture and enzyme-driven SeO₄^2-...

Understanding and controlling selective molecular interactions at bioelectronic interfaces are crucial for developing high-performance electrochemical sensors. In this work, we present a DNA-enzyme functionalized gold electrode for the dual-mode detection and precipitation of mercury (Hg(II)). The sensor utilizes thymine-rich DNA strands to selectively capture Hg(II), forming stable T-Hg(II)-T complexes, while an immobilized enzyme catalyzes the selective reduction of selenate (SeO₄^2-) to selenite (SeO₃^2-). The in situ-generated SeO₃^2- reacts with the bound Hg(II), triggering the precipitation of HgSeO₃ and facilitating the controlled release of mercury from the DNA scaffold. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) revealed distinct charge transfer resistance (R_CT) variations, corresponding to Hg(II) binding, SeO₄^2- reduction, and HgSeO₃ precipitation. The sensor exhibited exceptional selectivity, a detection limit in the sub-nanomolar range, and strong anti-interference performance from competing metal ions and oxyanions. Environmental sample testing further validated its applicability, showing high recovery rates (90.3-109.8 %). The results showed excellent agreement with the inductively coupled plasma mass spectrometry (ICP-MS) measurements as a conventional Hg(II) detection method. This work advances DNA-enzyme-mediated electrochemical sensing by integrating molecular recognition with an intrinsic detoxification mechanism. The findings provided a promising foundation for the next-generation bioelectronic platforms, enabling real-time monitoring of both inorganic mercury and selenate and a potential mercury removal method.