Development of a QCM-D biosensor for Ochratoxin A detection in red wine

Ochratoxin A (OTA), a highly toxic compound, is one of the most widely spread mycotoxins that contaminates a large variety of agricultural commodities. Due to its presence in the food chain, it imposes a hazard on both human and animal health. Therefore, there is a need for precise, fast and simple methods for toxin quantification. Herein, a novel sensor based on a quartz crystal microbalance with dissipation monitoring (QCM-D) and antibodies for specific analyte recognition was developed for rapid and sensitive detection of OTA in red wine. The combination of indirect competitive assay with QCM-D gives a straightforward device, which can simultaneously measure frequency (Δf) and dissipation (ΔD) changes resulting in detailed information about the mass attached to the sensor surface as well as conformational changes, viscoelastic properties and the hydration state of the film. Small molecules (such as OTA) suffer from poor LOD due to the high concentration of primary antibody needed to generate adequate signal. In the present study, amplification of the QCM-D signal was obtained by applying secondary antibodies conjugated with gold nanoparticles (AuNPs). Thanks to this, a linear detection range of 0.2-40ngmL^-1 has been achieved with an excellent LOD of 0.16ngmL^-1, which is one order of magnitude lower than LOD specified by European Union legislation concerning the limit of OTA in food. Moreover, a matrix effect (caused by the occurrence of polyphenols in wine) and associated non-specific interactions with the sensor surface was completely eliminated by a simple pre-treatment of the wine with the addition of 3% poly(vinylpyrrolidone) (PVP).