Abstract
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.
Highlights
The mycotoxin deoxynivalenol (DON) is a low molecular weight metabolite and chemical by-product of the fungal species Fusarium graminearum and Fusarium culmorum which occur naturally in the soil of crop fields and contaminate a wide range of crop plants before and after harvest [1]. It belongs to a class of mycotoxins called the trichothecenes which are commonly found in cereals or cereal-based food and feedstuffs
The sensor platform was prepared in stages as illustrated in Figure 3. (A) Nafion stock solution was diluted with 1:1 water to methanol mixture to yield 1% (v/v) solution and AuNp/G/PhNO2 was dispersed in the 1% (v/v) Nafion solution by ultra-sonication for 30 min to form 1 mg·mL−1 uniform nano-composite. 4 μL of it was drop-casted on the surface of a pre-cleaned glassy carbon electrode (GCE) and excess solvent was allowed to evaporate to dryness in the open at room temperature to form a thin film; (B) The
Nafion/AuNp/G/PhNO2 modified GC electrode was placed in 1 mM Ru(bpy)3Cl2 aqueous solution for 2 h to incorporate [Ru(bpy)3]2+ via electrostatic and ion-exchange interactions, forming a thin film modified glassy carbon electrode depicted as GCE/Nafion/[Ru(bpy)3]2+/AuNp/G/PhNO2
Summary
The mycotoxin deoxynivalenol (DON) is a low molecular weight metabolite and chemical by-product of the fungal species Fusarium graminearum and Fusarium culmorum which occur naturally in the soil of crop fields and contaminate a wide range of crop plants before and after harvest [1] It belongs to a class of mycotoxins called the trichothecenes which are commonly found in cereals or cereal-based food and feedstuffs. The analytical methods reported for the determination of DON include PCR, GC, GC-MS, HPLC, thin-layer chromatography and enzyme-linked immunosorbent assay (ELISA) [10,11,12,13,14,15,16] Some of these methods allow good accuracy of quantification and good detection limits, but they are not cost effective; some suffer from low selectivity and usually require significant amounts of time associated with labour-intensive sample cleanup, sophisticated instrumentation, skilled operators or technical expertise. The formation of immunocomplexes between DON antibody and DON antigenic species to which it selectively binds inhibited the electron flow and increased the charge transfer resistance of the sensing interface linearly, with the change in impedance being proportional to DON concentration
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