In-situ amplified voltammetric immunoassay for ochratoxin A by coupling a platinum nanocatalyst based enhancement to a redox cycling process promoted by an enzyme mimic

Abstract

A new signal amplified protocol for sensitive monitor of ochratoxin A was developed by coupling platinum enhancement technique to a redox cycling amplification strategy. Initially, platinum-enclosed gold cores (AuPtNP) were functionalized with monoconal antibody against ochratoxin A (OTA) to act as signal tags. Upon addition of analyte (OTA), competitive immunobinding occurs between OTA and an OTA-BSA conjugate immobilized on a ferrocene modified electrode for the anti-OTA on the signal tags. Next, the AuPtNPs on the immunosensor are incubated with a platinum enhancing solution to initiate the growth of additional catalysts in order to further promote the catalytic cycling between p-aminophenol and p-quinoneimine with the aid of the reductant NaBH4 and ferrocene. As a result, the analytical signal is strongly enhanced and can be measured by differential pulse voltammetry in the range from −300 mV to 600 mV (vs. SCE) at 50 mV s−1. Under optimized conditions, the immunosensor displays a dynamic working range that extends from 0.2 pg⋅mL−1 to 5 ng⋅mL−1 of OTA, with a lower detection limit of 75 fg⋅mL−1. The method is highly selective and was applied to the determination of OTA in (spiked) red wine samples.