Ochratoxin A (OTA) is a mycotoxin produced as a fungal secondary metabolite by several Aspergillus and Penicillium species growing on stored and processed agricultural products. The toxin causes carcinogenic, tetratogenic, estrogenic, nephrotoxic and immunosuppressive health conditions in both humans and animals. In humans, the consumption of food contaminated by OTA has been indicated to cause Balkan endemic nephropathy, a disease characterised by severe kidney damage. Currently, HPLC coupled to a fluorescent detector is the preferred method for testing for OTA and its metabolites. Thin-layer and gas chromatographic techniques as well as enzyme-linked immunosorbent assay have also been used to determine OTA. These methods have excellent sensitivities and limits of detection but require extensive sample pre-treatment, skilled labour and expensive equipment. On the other hand, electrochemical immunosensors are easy to use, require very minimal sample pre-treatment and detect low concentrations of target antigen. In this study, a direct electrochemical immunosensor for the detection of OTA was developed. Ochratoxin A antibody was immobilised onto a glassy carbon electrode modified with polyaniline-polystyrene nanocomposite doped with a novel bis[N-(phenyl)3,5-di-tert-butylsalicyladiminato]-
cobalt(II) complex. The biosensor’s ac and dc voltammetry characteristics were used to optimize the biosensor. Faradaic electrochemical impedance spectroscopy calibration of the nano-immunosensor responses was performed with aliquots of standard OTA solution in phosphate buffer (pH 7.2). Response profiles of the composite Ochratoxin A immunosensor include a detection limit of 80 μg/L and a sensitivity of 657 kW L/μg. The sensor was applied in the analysis of certified samples of maize meal, sorghum and poultry feed.

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1. End termination of commercial BDD electrodes with Sulphur and Nitrogen functionality for improved immobilisation of biomolecules.