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Fast and accurate determination of minute Ochratoxin A levels in flours: towards the application at the field
* 1 , 2 , 3 , 3 , 4 , 4 , 1 , 2 , 2
1  Immunopeptide chemistry Lab, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Centre for Scientific Research (NCSR) "Demokritos", Athens, Greece
2  Immunoassay/Immunosensors Lab, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Centre for Scientific Research (NCSR) “Demokritos”, Athens, Greece
3  Research, Innovation & Improvements of Food Operations Department, Jotis S.A. − Nutritional Foods Industry, Peristeri, Greece
4  ThetaMetrisis S.A., Polydefkous 14, 12243 Egaleo, Greece
Academic Editor: Giovanna Marrazza


Ochratoxins are a group of mycotoxins produced as secondary metabolites by several fungi of Aspergillus and Penicillium species. Ochratoxin A (OTA) is the most toxic member of the group and can be found in a large variety of highly consumed foods, such as coffee, cocoa, wine, and flour. Reliable determination of ΟΤΑ levels in food samples is therefore indispensable to assure compliance with national/European regulations concerning MRLs and consequently minimize health risks posed for living beings. In the current study, a label-free biosensor based on White Light Reflectance Spectroscopy (WLRS) for rapid and accurate determination of OTA in flour specimens is demonstrated. The transducer employed is a Si chip with a 1-μm thick thermal SiO2 on top, and is transformed to biosensing element through immobilization of a suitable OTA-protein conjugate on the SiO2 surface, while the determination is based on a dedicated competitive immunoassay format. For the assay performance, a mixture of an in-house developed anti-OTA antibody with the calibrators or the samples is injected over the chip surface followed by reaction with secondary biotinylated antibody and streptavidin for signal amplification. The WLRS biosensing platform allows for the label-free, real-time monitoring of biomolecular interactions carried out onto the SiO2/Si chip by transforming the shift in the reflected interference spectrum caused by the immunoreaction to effective biomolecular adlayer thickness. After optimization, the sensor was capable of real-time detection of OTA in flour samples with LoD of 60 pg/mL, within 25 min total analysis time. The intra- and inter-assay CVs were ≤5.9% and ≤9.0%, respectively. The excellent analytical characteristics and short analysis time in combination with its small size render the proposed WLRS system ideal for the quantitative determination of minute OTA levels at the Point-of-Need for food-, environment-, and health-related purposes.

Keywords: mycotoxins; ochratoxin A; flour; white light reflectance spectroscopy; label-free immunosensor, Point-of-Need