One stone towards two birds: Y-shaped DNA probe and rGO-AuNPs aerogel-driven electrochemical aptasensor for AFB and OTA co-detection.

The widespread co-contamination of aflatoxin B (AFB) and ochratoxin A (OTA) in food and other complex matrices poses significant challenges for their on-site monitoring. Here, a highly selective and sensitive electrochemical (EC) aptasensor based on Y-shaped DNA probe as specific recognition element and Nafion-immobilized reduced graphene oxide-gold nanoparticles (rGO-AuNPs) aerogel nanocomposite as signal amplification unit was developed for the simultaneous determination of trace AFB and OTA. rGO-AuNPs aerogel was uniformly distributed and firmly fixed on the Au electrode surface through Nafion film, which with large specific surface area and excellent electrical conductivity provided numerous active sites for coupling with Y-shaped DNA probes to amplify electrical signals of ferrocene (Fc) and methylene blue (MB) to improve the detection performance. In the presence of AFB and OTA, they were specifically bound by the functionalized aptamers in the Y-shaped DNA probes, leading to the release of electrical signal molecules (Fc and MB) and the reduction of the amplified current signals, which were recorded for simultaneous quantitation of AFB and OTA. Under optimal conditions, the newly-developed EC aptasensor exhibited high selectivity, good stability, remarkable reproducibility, and excellent sensitivity with ultra-low LODs of 0.86 pg/mL for AFB and 0.723 pg/mL for OTA, respectively. The successful application in malt and lotus seeds samples underscored its feasibility and accuracy for simultaneously detecting AFB and OTA to really achieve the purpose of "one stone towards two birds". The proposed EC aptasensing platform boasted broad application prospects in food safety, environmental monitoring, and clinical fields.