Photoelectrochemical aptasensor for detection of Ochratoxin A in synthetic red wine samples

The detection of Ochratoxin A (OTA) in wine samples is crucial for ensuring the safety and quality of wine products. Addressing this need, a photoelectrochemical aptasensor composed of electrochemically synthesized zinc oxide nanorods (ZnO-NRs), cadmium sulfide nanofibers (CdS) deposited via chemicalp bath deposition, gold nanoparticles (Au-NPs) obtained through electrochemical reduction and selective aptamers added by drop casting has been developed. The ZnO-NRs provide a high surface area, while CdS nanofibers enhance photoelectrochemical properties, Au-NPs facilitate electron transfer, and the aptamers offer high selectivity towards OTA. The morphology and structure of the synthesized compounds were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction (XRD). Evaluation of the aptasensor’s performance in synthetic wine samples demonstrated that the photocurrent signal significantly improves sensor sensitivity compared to dark conditions, owing to the enhanced electron transfer upon photoexcitation of the CdS semiconductor. The aptasensor achieved a limit of detection (LOD) and limit of quantification (LOQ) of 0.5 μg/L and 1.8 μg/L, respectively, surpassing the European Union’s OTA threshold of 2 μg/L in wines. These findings highlight the potential application of the developed aptasensor in the wine export industry and open new avenues for the development of photoelectrochemical biosensors for various analytes by modifying the aptamer.