A novel electrochemical sensor for ochratoxin A based on the hairpin aptamer and double report DNA via multiple signal amplification strategy

A novel electrochemical sensor for ochratoxin A (OTA) based on the hairpin aptamer (HA) and double report DNA was constructed successfully. In the work, HA was chosen as the OTA recognition element and immobilized on the gold electrode (GE) via Au-S. Au nanoparticles (AuNPs) labeled double report DNA (rDNA1 and rDNA2) were symmetrically hybridized with HA simultaneously. Compared to the single report DNA, the strategy can dramatically increase the amount of AuNPs on the electrode surface and the stability of the HA to prevent lodging. The signal amplification was further implemented by using trithiocyanuric acid (TCA) to aggregate the AuNPs. Thus, it was observed that the differential pulse voltammetry (DPV) response of AuNPs was significantly amplified via multiple signal amplification strategy. When OTA was present, the HA was specifically combined with OTA to form the OTA-HA complex, which caused double report DNA to detach from the electrode, resulting in the decrease of the DPV response. The proposed electrochemical aptasensor can sensitively detect low concentrations of OTA by monitoring the OTA-dependent DPV intensity change. Under the optimized conditions, it exhibited wide linear ranges from 1 pg mL(-1) to 1 ng mL(-1) with a low detection limit of 0.5 pg mL(-1). The work provides a new idea for the various mycotoxins and even other substances detection at trace level.