Electrochemical detection of selenate using ferrocene peptide-mediated enzymatic biosensor at gold nanodendritic surfaces†

The ferrocene-conjugated peptide acted as the redox mediator to aid in electron transfer to selenate reductase immobilized at the gold nanodendritic surfaces and provided an enhanced sensitivity for the catalytic reduction of selenate (SeO 4 2- ) to selenite (SeO 3 2- ). The calibration studies were performed using differential pulse voltammetry under optimized conditions with a wide linear range and a limit of detection (LOD) of 5.7 × 10 −4 μg/L. This LOD was an 18-fold improvement over the one obtained using a non-mediated biosensor. Other oxyanions, including SO 4 2 , NO 3 - , PO 4 3- , SeO 3 2- , AsO 4 3- and AsO 3 3- , did not interfere significantly with the electrochemical detection of selenate. At high concentrations of these oxyanions, the LOD for selenate detection remained virtually unaffected, suggesting that the biosensor might have utility for selenate detection in real matrices. For this purpose, the spiked mine tailings were used as real samples displaying a recovery between 96.9 and 103.1 %. Based on the preliminary results, the ferrocene peptide-mediated enzymatic biosensor demonstrated to be a promising tool for sensitive and selective monitoring of selenate toward future applications in the on-site validation of selenium pollution as well as the pre-treatment strategies for selenium removal across diverse environmental matrices. • First-ever electrochemical sensor for selenate using a redox mediator. • The use of a mediator lowers the limit of detection by a factor of more than 200 compared to an unmediated system. • Low interference from other oxoanions. • Good long-term stability.