Multifunctional magnetic bead-based electrochemical immunoassay for the detection ofaflatoxin 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.