Application of Gold Nanoparticles for High-Sensitivity Fluorescence Polarization Aptamer Assay for Ochratoxin A

Abstract

The use of gold nanoparticles (GNPs) as carriers for the decrease in the detection limit of a fluorescence polarization (FP) aptamer assay is proposed. The common FP assay is based on the use of polarized exciting light and changes in the polarization of emitted light by the fluorophore–analyte conjugate before and after its binding with a receptor of the target analyte. Aptamers’ application as receptors in such an assay is limited due to their low molecular weight and, consequently, insufficient influence on polarization of emitted light. This limitation can be overcome by the inclusion of aptamers in larger intermolecular complexes. In the present work, the advantages of GNPs as unified, stable, and simply modified carriers for aptamers are demonstrated. The FP aptamer assay is realized with the use of GNPs with average diameter of 8.7 nm and ochratoxin A (OTA) as the target analyte. Finally, the assay is tested for OTA control in spiked white wine. The reached limit of detection is 2.3 µg/kg, which is 25-fold lower as compared to native aptamer. The time of the assay is 15 min. The universality of the proposed approach makes it possible to use aptamers for FP assays of various low-molecular-weight substances.