One-step and real-time detection of Hg in brown rice flour using a biosensor integrated with AC electrothermal enrichment.

Mercury (Hg) is one of the most toxic heavy metals in farm products, so rapid detection of trace Hg has always been sought after with high interest. Herein, we report a biosensor to specifically recognize Hg in leaching solutions of brown rice flour. This sensor is simple and of low cost, with a very short assay time of 30 s. Another merit is the ultra-low limit of detection (LOD) at fM level. In addition, the specific aptamer probe realizes a good selectivity above 10: 1 against the interferences. This sensor is developed based on an aptamer-modified gold electrode array (GEA) for capacitive sensing. Alternating current electrothermal (ACET) enrichment is induced during the AC capacitance acquirement. Thus, the enrichment and detection are coupled as a single step, and pre-concentration is needless. Owing to the sensing mechanism of solid-liquid interfacial capacitance and ACET enrichment, Hg level can be sensitively and rapidly reflected. Also, the sensor has a wide linear range from 1 fM to 0.1 nM and a shelf life of 15 days. This biosensor shows advantages on overall performance, enabling easy-to-operate, real-time, and large-scale Hg detection in farm products.