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A Highly Sensitive and Robust Biosensor for Fungal Toxins

DNA-based disposable electrochemical sensor allows detection of mycotoxins

Akkapol Suea-Ngam from our group has developed a novel, cost-effective and disposable biosensor for the detection of fungal toxins (mycotoxins). This biosensor shows high sensitivity of detection whilst being robust and easy to use.

Mycotoxins have proven dangerous and, in some cases, carcinogenic to humans and animals. One of the most common mycotoxins found in plant-based food and beverages is Ochratoxin A (OTA). Due to its triple threat of prevalence, accumulation in meat produce and toxicity in small amounts, this toxin necessitates a sensitive and robust detection method that allows quality control in every step of the food production process.

In this work, a biosensor was designed with enhanced selectivity and sensitivity to target OTA. This sensor consists of three components: a disposable electrode, short single-stranded DNA (ssDNA) molecules (aptamers) and the silver metal ions. The disposable electrode is the base of the sensor and serves as a transducer. This base is functionalized with aptamers, which show a high binding specificity towards molecular targets. The aptamers wrapped around the OTA in the sample, inhibiting digestion from Exonuclease I, an enzyme which selectively degrades ssDNA. Hence, the unbound aptamers were removed from the sensor surface. Aptasensors are both cheap and efficient, but show deficits in sensitivity and density on the sensor surface. Therefore, Akkapol developed an OTA detection method using silver metallization of the aptamers for signal enhancement. Silver ions, deposited on the aptamer surface, were reduced to silver metal chemically and electrochemically, allowing for a highly sensitive electrochemical signal detection.

This method performs at a detection limit of 0.7 pg/mL in a range from 1 pg/mL to 0.1 µg/mL, which exceeds the reported levels of detection of previous electrochemical techniques. Further, the sensor was successfully tested on OTA spiked beer samples in a range from 1 to 100 ng/mL with an accuracy of max. 2.5 %. Although developed for OTA detection, this sensor shows the versatility to be adapted for the detection of other toxins and contaminants, making this biosensor a promising tool for future electrochemical aptasensors.

Written by Julia Nette.

Read the full paper here.

The aptamer-functionalized gold electrode used for detection of Ochratoxin A

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