Fast and sensitive detection of ochratoxin A in red wine by nanoparticle-enhanced SPR

Herein, we present a fast and sensitive biosensor for detection of Ochratoxin A (OTA) in a red wine that utilizes gold nanoparticle-enhanced surface plasmon resonance (SPR). By combining an indirect competitive inhibition immunoassay and signal enhancement by secondary antibodies conjugated with gold nanoparticles (AuNPs), highly sensitive detection of low molecular weight compounds (such as OTA) was achieved. The reported biosensor allowed for OTA detection at concentrations as low as 0.75 ng mL⁻¹ and its limit of detection was improved by more than one order of magnitude to 0.068 ng mL⁻¹ by applying AuNPs as a signal enhancer. The study investigates the interplay of size of AuNPs and affinity of recognition elements affecting the efficiency of the signal amplification strategy based on AuNP. Furthermore, we observed that the presence of polyphenolic compounds in wine samples strongly interferes with the affinity binding on the surface. To overcome this limitation, a simple pre-treatment of the wine sample with the binding agent poly(vinylpyrrolidone) (PVP) was successfully applied.