Aptamer-modified pencil graphite electrodes for the impedimetric determination of ochratoxin A

Ochratoxin A (OTA), a widespread food contaminant, is considered as one of the most hazardous mycotoxins commonly occurring in beer. Herein, we describe a novel impedimetric aptasensor based on Pencil Graphite Electrodes (PGE) for the analysis of OTA. Taking advantage of its affordability and high active surface area, a PGE was modified with a specific aptamer, to achieve sensitive detection of OTA. This strategy relies on the target-induced increase in the electron transfer resistance (Rct) upon OTA recognition using ferro/ferricyanide as a redox probe. With the addition of OTA, the formation of OTA–aptamer complex resulted in an increase of Rct. The change of Rct strongly depends on OTA concentration, which is applied for mycotoxin quantification. An acceptable linear range was obtained from 0.1 to 2.0 ng mL−1 with a very good limit of detection as low as 0,1 ng mL−1. This simple-to-design aptasensor was successfully tested in spiked beer samples, with OTA concentrations in the range of 0.4–1.6 ng mL−1, attesting a recovery percentage of 93.4 ± 6.6%. It also showed a high level of stability and reproducibility thanks to the electro-grafting method via in-situ generation of 4-carboxyphenyl diazonium salts. This PGE-based platform is a versatile approach for the design of low-cost aptasensors for food safety control.