A simple label-free photoelectrochemical immunosensor for highly sensitive detection of aflatoxin B1 based on CdS–Fe3O4 magnetic nanocomposites

Abstract

A simple label-free photoelectrochemical (PEC) platform was developed based on magnetic CdS–Fe₃O₄ nanocomposites and used for detection of aflatoxin B₁ (AFB₁). CdS quantum dots (QDs) were successfully assembled on mesoporous Fe₃O₄ NPs via covalent binding and employed as the photoactive materials on the surface of screen-printed electrode (SPE). H₂O₂ was employed as a sacrificial electron donor for scavenge photo-generated holes in the valence band of CdS QDs. Anti-aflatoxin B₁ (anti-AFB₁) was conjugated onto CdS–Fe₃O₄ nanocomposites modified SPE by using the classic EDC coupling reactions between the carboxy group (–COOH) groups on the surfaces of the TGA capped CdS QDs and the amino group (–NH₂) groups of the antibody (Ab). The concentrations of AFB₁ were measured through the decreased photocurrent resulting from the increased steric hindrances due to the formation of the immunocomplex. Under the optimal conditions, the PEC biosensor for AFB₁ determination exhibited a linear range from 0.01 ng mL⁻¹ to 80 ng mL⁻¹ with a detection limit of 5.0 pg mL⁻¹. Besides, the PEC biosensor has been applied in the corn samples detection. The proposed PEC biosensor is simple, sensitive, fast and stable, which opens up a new promising PEC platform for other small molecules analysis.