Electrochemical DNA aptamer-based biosensor for OTA detection, using superparamagnetic nanoparticles

A novel electrochemical aptasensor, based on disposable screen-printed electrodes was developed for the sensitive detection of the mycotoxin ochratoxin A (OTA). Two strategies were investigated by using an indirect and a direct competitive assay, based on the use of superparamagnetic nanoparticles. The performance of the optimized aptasensors in terms of reproducibility, stability, sensitivity, and analysis time was studied. The best strategy was found to be the direct competitive format. In this assay, free OTA competed with labeled alkaline phosphatase–OTA for the binding to the DNA aptamer immobilized on magnetic beads. The electrochemical detection was thus achieved through a suitable substrate for the enzyme ALP, by Differential Pulse Voltammetry. The aptasensor obtained using this novel approach allowed detection limit of 0.11 ng/mL, and was also validated for real sample analysis.