Multifunctional magnetic bead-based electrochemical immunoassay for the detection of aflatoxin B₁ in food

A sensitive and reusable electrochemical immunoassay for aflatoxin B₁ (AFB₁) in food has been developed. A multifunctional magnetic bead (MMB) was initially synthesized using magnetic CoFe₂O₄ nanoparticle as the core and Prussian blue nanoparticle (PBNP)-doped silica as the shell, and then the prepared MMB was used as an affinity support for the immobilization of the AFB₁–bovine serum albumin conjugate (AFB₁–BSA). With the aid of an external magnet, the AFB₁–BSA-conjugated MMBs were attached on the surface of an indium tin oxide (ITO) electrode. Gold nanoparticles, labeled with horseradish peroxidase (HRP)-bound anti-AFB₁ antibodies (HRP-anti-AFB₁), were employed as detection antibodies. With a competitive immunoassay format, the concentrations of AFB₁ in samples were measured in PBS (pH 7.0) by using PBNP-doped MMBs as the mediator, HRP-anti-AFB₁ as the tracer and hydrogen peroxide (H₂O₂) as the enzyme substrate, and the linear range was 0.05–12 ng/mL with a detection limit of 6.0 pg/mL AFB₁ (at 3σ). Intra- and inter-assay coefficients of variation were less than 7.5%. In addition, the content of AFB₁ in red paprika specimens has been assayed by the developed immunoassay and a commercially available enzyme-linked immunosorbent assay (ELISA) method, respectively, and consistent results were obtained. The as-prepared immunoassay provides a promising approach for the screening of organic pollutants because it is simple, rapid, highly sensitive, specific, and without the need of sample pre-concentration.