Development and modeling of an ultrasensitive label-free electrochemical immunosensor for okadaic acid based on polythionine-modified three-dimensional gold nanoelectrode ensembles

A novel ultrasensitive and label-free electrochemical immunosensor was developed and used in combination with electrochemical impedance spectroscopy (EIS) or square wave voltammetry (SWV) for okadaic acid (OA) detection. The prepared immunosensor is primarily composed of polythionine-modified three-dimensional gold nanoelectrode ensembles (3DGNEEs). These ensembles were fabricated by combining electroless and electrochemical deposition. The deposition potential and time of the electrodeposition were optimized to enhance the properties of the 3DGNEEs. OA antibodies (anti-OA) were fixed on the PTh-modified ensembles by glutaraldehyde (GA). The fabrication process of immunosensor was characterized by EIS. The EIS responses were simulated using a newly constructed model of the recognition interface, and the detection limit of SWV is lower than that of EIS (3.20 × 10⁻¹⁵ vs. 2.65 × 10⁻¹² g mL⁻¹), and the linear OA detection range of the former is wider (1 × 10⁻¹²–1 × 10⁻⁷ vs. 5 × 10⁻¹²–1 × 10⁻⁹ g mL⁻¹).