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-Mn2+). 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-Mn2+ were captured onto the electrode surface, which could induce the in situ formation of MnO2via classical redox reaction between Mn2+ and KMnO4 on the immunesensing platform. Moreover, the generated MnO2 nanoparticles act as efficient catalyst could catalyze the 4-chloro-1-naphthol (4-CN) oxidation without H2O2 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 0.1pgmL−1 and 30ngmL−1. The detection limit (LOD) of the assay was 0.055pgmL−1. The developed method exhibited high selectivity and can be used for the determination of OTA in real red wine samples. •An facile impedimetric immunoassay was developed for OTA based on instant catalyst.•The instant catalyst can be formed on the immunosensing platform in 1 min.•The instant catalyst could catalyze the 4-CN oxidation without H2O2.•The PAMAM can load with multiple Mn2+ ions.