Nafion-based label-free immunosensor as a reliable warning system: The case of AFB1 detection in cattle feed

Abstract

This study presents a simple method for the rapid and versatile fabrication of label-free immunosensors on Nafion-modified screen-printed platforms. Herein, Nafion is exploited both as an immobilization matrix and as a weak (unexpectedly) electrochemical enhancer for the first time. The electrochemical characteristics in terms of diffusivity and conductivity of thin cation-exchange polymer membrane-modified screen-printed electrodes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The free electrode surface area, the diffusion coefficient, the peak-to-peak separation, the heterogeneous electron transfer constant, and the charge transfer resistance for Nafion-modified and bare SPE have been calculated and compared. Then, Nafion-SPEs were employed to develop a competitive label-free immunoassay for the quantitative detection of Aflatoxin B1. Morphological characterization of the proposed immunosensor was performed using Scanning Electron Microscopy, and its analytical performance was evaluated using square wave voltammetry as a detection technique and [Fe(CN)6]3−/4− as a redox probe. The immunosensor showed satisfactory results in spiked cattle feed in terms of limit of detection (3.8 ngmL−1), linear range (LR 10–100 ngmL−1), sensitivity (33.0 ngmL−1) and reproducibility (RSD%<10%). The comparison of performance to that of a labelled immunosensor and a conventional chromatographic technique revealed a strong correlation between the respective results, but with shorter analysis time for the proposed tool. Furthermore, The present study achieved evidence of the dependability of the proposed method, proving that its use as an early warning system for the detection of AFB1 in cattle feed is something doable and not an abstract idea.