Ochratoxin A (OTA) is a mycotoxin produced by several fungal species and various studies have shown that OTA can cause several adverse health effects to animals and humans through its consumption in contaminated plant foods such as coffee, beer, wine, corn, wheat, oats and vegetables . OTA has been shown to be nephrotoxic, teratogenic, immunotoxic, and carcinogenic in human health. In particular, the International Agency for Research on Cancer has classified OTA as a group 2B carcinogen . Due to the toxicity of OTA , the European Union has set maximum limits (MLs) for OTA in foods in the range of 0.5–10 μg kg−1 . Therefore, the development of a cheap, sensitive and rapid method for OTA detection in plant-based foods is essential.
The detection of OTA in food is mostly based on chromatographic techniques, which although powerful , require expensive equipment, trained personel and complex sample preparation [1,2]. Enzyme-linked immunosorbent assay s(ELISA) and immunochromatographic assays are portable, convenient and simple but require expensive and unstable antibodies and normally [3,4]. On the contrary aptamer-based biosensors employ relative inexpensive and stable single stranded oligonucleotides as biorecognition elements, which makes them ideal for rapid on-site detection of OTA [2,5], especially when combined with smartphone-based detection .
In this work, we describe a simple, portable and cost-efficient lateral flow biosensor for OTA. The biosensor utilizes an OTA-specific aptamer for biorecognition and is based on a lateral flow assay using a device consisting of a sample pad, a conjugate pad, a test and a control zone, as well as an absorbent pad. The conjugate PAD is loaded with OTA aptamer-AuNPs congugates while the test and control zones are loaded with a specific and a universal probe, respectively. The principle of the assay is that the OTA present in the sample combines with the OTA aptamer-AuNPs congugates and prevents the interaction between the specific probe in the test line and the OTA aptamer-AuNPs congugates; therefore, the intensity of the test line decreases as the concentration of OTA in the sample increases. Quantification of OTA is performed by reflectance calorimetry using a smartphone and image analysis. All the parameters of the assay were investigated in detail and the analytical features were established.
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