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

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 Mi-croscopy, 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 con-ventional 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 depend-ability 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.