In this paper, we report a new concept to construct a label-free electrochemical inhibition-based immunosensor for the detection of the mycotoxin deoxynivalenol (DON) in cereal samples. The electrochemical impedance spectroscopy of tris(bipyridine) ruthenium (II) chloride was used as a marker enhanced with gold nanoparticles-dotted 4-nitrophenylazo functionalized graphene (AuNp/G/PhNO₂) nanocatalyst mediated in Nafion on a glassy carbon electrode. Under the optimized conditions, the formation of immunocomplexes inhibited electron flow and increased the charge transfer resistance of the sensing interface linearly. The change in impedance was proportional to DON concentrations in the range of 6–30 ng/mL with a sensitivity and detection limit of 32.14 ΩL/ng and 0.3 µg/mL, respectively, which compares favorably with the ELISA result. The proposed sensor had a stability of 80.3%, good precision and selectivity in DON standard solution containing different interfering agents, indicating promising application prospect for this strategy in designing impedimetric, electrochemiluminescent, voltammetric or amperometric sensors.

An impedimetric immunosensor for fumonisins was developed based on poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes doped with palladium telluride quantum dots onto a glassy carbon surface. The composite was assembled by a layer-by-layer method to form a multilayer film of quantum dots (QDs) and poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes (PDMA-MWCNT). Preparation of the electrochemical immunosensor for fumonisins involved drop-coating of fumonisins antibody onto the composite modified glassy carbon electrode. The electrochemical impedance spectroscopy response of the FB₁ immunosensor (GCE/PT-PDMA-MWCNT/anti-Fms-BSA) gave a linear range of 7 to 49 ng L⁻¹ and the corresponding sensitivity and detection limits were 0.0162 kΩ L ng⁻¹ and 0.46 pg L⁻¹, respectively, hence the limit of detection of the GCE/PT-PDMA-MWCNT immunosensor for fumonisins in corn certified material was calculated to be 0.014 and 0.011 ppm for FB₁, and FB₂ and FB₃, respectively. These results are lower than those obtained by ELISA, a provisional maximum tolerable daily intake (PMTDI) for fumonisins (the sum of FB₁, FB₂, and FB₃) established by the Joint FAO/WHO expert committee on food additives and contaminants of 2 μg kg⁻¹ and the maximum level recommended by the U.S. Food and Drug Administration (FDA) for protection of human consumption (2–4 mg L⁻¹).

Nanoparticles are considered unique sensing material as they are small and deliver sensitivity as low as parts per billion compared to their bulk counterparts used in the conventional devices. Zinc Oxide (ZnONPs) nanoparticles are considered one of the promising sensing materials due to their high surface-to-volume ratio compared to other conventional sensing materials. They have been found useful for sensing of hydrogen gas, carbon monoxide, ammonia and ethanol. Ethanol sensing forms a platform for monitoring various processes in medical and food industries. Herein, zinc oxide nanoparticles were synthesized using Spathodea campanulata plant extract as reducing and stabilizing agent. The biosynthesized nanoparticles were used to fine tuning a glassy carbon electrode (GCE) for ethanol sensing. Ethanol sensing capability of the modified GCE electrode was gauged upon its amperometric responses to different ethanol concentrations. The high surface to volume ratio of the nanoparticles greatly enhanced peak currents of the modified electrodes leading to signal towards ethanol detection.