Amplified impedimetric immunosensor based on instant catalyst for sensitive determination of ochratoxin A

A new impedimetric immunosensor for the fast determination of ochratoxin A (OTA) in food samples was developed based on the instant catalyst as enhancer. Initially, the signal tags were prepared via co-immobilization of anti -OTA antibody and amine-terminated dendrimer (PAMAM) on the graphene oxide nanosheets through the covalent interaction, which were utilized as a good platform for combining manganese ion ( anti -OTA-GO-PAMAM-Mn 2+ ). Upon target OTA introduction, a competitive-type immunoreaction was implemented between the analyte and the immobilized OTA-BSA on the electrode for the anti -OTA antibody on the graphene oxide nanosheets labels. After a competitive immunoassay format, the anti -OTA-GO-PAMAM-Mn 2+ were captured onto the electrode surface , which could induce the in situ formation of MnO 2 via classical redox reaction between Mn 2+ and KMnO 4 on the immunesensing platform. Moreover, the generated MnO 2 nanoparticles act as efficient catalyst could catalyze the 4-chloro-1-naphthol (4-CN) oxidation without H 2 O 2 to generate an insoluble precipitation on the platform. Under the optimal conditions, the instant catalyst based impedimetric immunosensor displayed a wide dynamic working range between 0.1   pg   mL −1 and 30   ng   mL −1 . The detection limit (LOD) of the assay was 0.055   pg   mL −1 . The developed method exhibited high selectivity and can be used for the determination of OTA in real red wine samples.