Immunoassay for ochratoxin A (OTA) on magnetic particles with smartphone-based electrochemical detection of TMB (3,3’,5,5’- Tetramethylbenzidine)
Source: BAM department Analytical Chemistry; Reference Materials and department Materials Chemistry
The contamination of food by mycotoxins poses a severe health risk to humans and animals. Therefore, the European Commission has set legal limits for several mycotoxins, such as ochratoxin A (OTA). Many companies in food industry have their own laboratories to control mycotoxin contamination. However, the mycotoxin analysis is time-consuming and needs trained personnel.
The antibody-based detection method, ELISA (Enzyme-linked immunosorbent assay), with photometric detection of the chromogen, TMB (3,3’,5,5’-tetramethylbenzidine), forms a good basis for sensitive detection. However, devices for photometric detection are difficult to miniaturize. Electrochemical methods offer great promise in meeting the demand for on-site devices for monitoring mycotoxins.
To provide a straightforward approach for the miniaturization of the detection step in ELISA, the pitfalls of the electrochemical TMB detection were studied. A stable electrochemical signal is an important prerequisite for performing analytical measurements. It was found that the TMB electrochemistry is strongly dependent on the pH and the electrode material. A stable electrode response to TMB could be achieved at highly acidic conditions on gold electrodes, whereas carbon electrodes and a weakly acidic pH value do not allow reliable detection of TMB. Based on these results, an immunoassay for OTA on magnetic microparticles was developed. The results obtained with the developed electrochemical method are in good correlation with the well-established optical method.
Furthermore, the applicability of the immunomagnetic assay for OTA in beer was demonstrated. Here a handheld device for electrochemical detection connected via Bluetooth to a smartphone was used. The beer samples were spiked with OTA and with the immunoassay and electrochemical detection traces of OTA could be quantified (0.5 μg L−1). The developed detection system is highly promising to connect many immunoassays with smart technologies, and it represents a miniaturized and low-cost alternative to traditional optical detection.
Electrochemical Immunomagnetic Ochratoxin A Sensing: Steps Forward in the Application of 3,3’,5,5’- Tetramethylbenzidine in Amperometric Assays
Soraya Höfs, Deniz Hülagü, Francesca Bennet, Peter Carl, Sabine Flemig, Thomas Schmid, J. A. Schenk, Vasile-Dan Hodoroaba, Rudolf J. Schneider
published in ChemElectroChem, Vol. 8, issue 13, pages 2597-2606, 2021
BAM department Analytical Chemistry; Reference Materials and department Materials Chemistry