Development of a Sensitive Cysteine-Modified Au-NPs–Graphene Nanoribbons Nanocomposite Disposable Biosensor for Aflatoxin B1 Detection in Food samples

A simple and sensitive electrochemical biosensor based on a disposable graphite pencil electrode (PGE) is proposed for the detection of aflatoxin B1 (AFB1) in food samples. The biosensor utilized graphene nanoribbons (GNRs)–gold nanoparticles (Au-NPs) nanocomposites as the sensing material, with cysteine (Cys) and antiaflatoxin B1 (anti-AFB1) antibody serving as the detection probe. GNRs were produced by the oxidative unzipping of multiwalled carbon nanotubes (MWCNTs), followed by the electrodeposition of Au-NPs on GNRs-modified PGE and surface modification with Cys. Various characterization techniques were employed to analyze the MWCNTs, confirm the formation of GNRs, and verify the GNRs–Au-NPs nanocomposite. Electrochemical methods, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), were used to characterize each step of the biosensor fabrication. EIS was initially applied to test the designed biosensor for detecting AFB1 in phosphate-buffered saline (PBS) and later in spiked maize samples containing varying concentrations of the target analyte. The biosensor response was validated by using CV and differential pulse voltammetry (DPV). The biosensor demonstrated a good linear response over the investigated concentration range, with a limit of detection (LOD) of 0.06 ng mL–1, improved selectivity, higher repeatability, and stable performance over 24 days. Additionally, the sensor exhibited a good percent recovery when detecting AFB1 in spiked maize samples.