Development of a label-free electrochemical aptasensor for ultrasensitive detection of ochratoxin A. (May 2022) - Hou, Yujiao
Abstract: The prevalent ochratoxin A (OTA) contamination in food has increased the urgency to develop sensitive and accurate detection methods. This study reported a conveniently fabricated label-free electrochemical (EC) aptasensor for ultrasensitive detection of OTA based on the competitive binding of OTA with its specific aptamer without any signal amplification strategy. A gold electrode (AuE) was modified with a compact layer of double-stranded DNA (dsDNA), obtained via OTA aptamer and complementary DNA (cDNA) hybridization, to act as a barrier for redox probe [Fe(CN)6 ] 3-/4- to AuE access. This led to a high initial electron-transfer resistance (Rct ), recorded via electrochemical impedance spectroscopy (EIS). Since the aptamer displayed a higher affinity to OTA than cDNA, the added OTA triggered aptamer dissociation from AuE to form the OTA-aptamer complex, obviously decreasing the Rct . The target-induced variation in the resistance response strongly depended on the OTA concentration. Optimum conditions improved the linear relationship between Rct and the logarithm of OTA concentration in a range of 0.05–10 ng/mL with a limit of detection (LOD) of 0.05 ng/mL for OTA. Recoveries of 74.8–105% with relative standard deviations (RSDs) of 8.86–13.09% were obtained in the spiked malt samples. The Real-world detection of OTA in the actual malt samples confirmed the reliability of the convenient, cost-effective, and highly specific impedimetric aptasensor, exhibiting significant promise for extended application in food control to identify more hazardous contaminants by altering the corresponding aptamers. Highlights: A label-free electrochemical impedimetric aptasensor for OTA detection was developed. No extra coupling medium was involved for immobilizing the aptamers. The aptasensor achieved high sensitivity for OTA without signal amplification. The impedimetric aptasensor succeeded in real malt samples with satisfactory recoveries. The aptasensor can be extended to more contaminants in foods via replacing the corresponding aptamers.