A gold/Fe₃O₄ nanocomposite for use in a surface plasmon resonance immunosensor for carbendazim

A surface plasmon resonance (SPR) biosensor for the pesticide carbendazim is described that has enhanced performance due to the use of a Au/Fe₃O₄ nanocomposite as an amplifying label on the surface the carboxymethyldextran-coated gold layer of the sensor. The surface was further modified with monoclonal antibody to obtain a sensor for real-time detection of carbendazim. Binding of carbendazim results in a change in refractive index. SPR detection in the absence of Au/Fe₃O₄ nanocomposite and by UPLC-MS analysis demonstrated the improved performance to be due to the use of the Au/Fe₃O₄ nanocomposite. Response is linear in the 0.05 to 150 ng·mL^-1 carbendazim concentration range, and the limit of detection is 0.44 ng·mL^-1. This is more than 1 order of magnitude lower than that of the conventional SPR assay. The recoveries from spiked medlar are between 102.4 and 115.0%. The selectivity was tested by using the pesticides benzimidazole, 2-mercaptobenzimidazole, 2-benzimidazole propionic acid, and 2-(2-aminoethyl) benzimidazole as potential interferents. Conceivably, this Au/Fe₃O₄ nanocomposite-based method has a large potential for the detection of other small analytes at trace concentrations. Graphical abstract Schematic presentation of the SPR sensor for the detection of the fungicide carbendazim (methyl 2-benzimidazole carbamate; MBC) based on the use of a gold/Fe₃O₄ nanocomposites.