Electrogenerated Chemiluminescence Immunosensor for Bacillus thuringiensis Cry1Ac Based on Fe3O4@Au Nanoparticles

A highly sensitive electrochemiluminescence (ECL) immunosensor for Cry1Ac was fabricated. The primary antibody anti-Cry1Ac was immobilized onto core–shell structural Fe3O4@Au nanoparticles. The antigen and glucose-oxidase-labeled secondary antibody were then successively combined to form sandwich-type immunocomplexes through a specific interaction. The magnetic particles loaded with sandwich immune complexes were attracted to a magnet-controlled glass carbon electrode (GCE) by an external magnet applied on top of the GCE. ECL was generated by the reaction between luminol and hydrogen peroxide derived from the enzymatic reaction in the presence of glucose. The sensors exhibited high sensitivity and a wide linear range for Bacillus thuringiensis Cry1Ac detection from 0 to 6 ng/mL, as well as a detection limit of 0.25 pg/mL (S/N = 3). The sensor is one of the most sensitive sensors for Cry1Ac, which can be easily renewed and conveniently used.