A lateral flow immunoassay for the rapid detection of ochratoxin A in wine and grape must

A one-step lateral flow immunoassay was developed for semiquantitatively detecting ochratoxin A (OTA) in wines and grape musts. Matrix-matched calibration curves carried out in blank wines showed a detection limit of 1 μg L(-1) and IC(50) of 3.2 μg L(-1). Relative standard deviations for intra- and interday precision were in the 20-40% range. A simple treatment of samples, which only included dilution with sodium bicarbonate and polyethylene glycol (4% w/v) for red and white wines and the further addition of ethanol (12% v/v) for grape musts, was established. The developed assay allowed OTA detection in 5 min and proved to be accurate and sensitive enough to allow the correct attribution of samples as compliant or noncompliant according to EU legislation. Results agreeing with those of a reference chromatographic method were obtained on 38 wines and 16 musts. Although some lateral flow devices aimed at detecting OTA have been previously described, this is the first assay capable of measuring the toxin in wine and grape must, which represent a major source of OTA dietary intake. Analytical performances of the method are comparable to or better than previously reported assays showed. In addition, the assay, including sample treatments, is extremely simple and rapid and can be effectively regarded as a one-step assay usable virtually anywhere.

Analytical performances of a DNA-ligand system using time-resolved fluorescence for the determination of ochratoxin A in wheat

The analytical performances of a novel DNA-ligand system using the time-resolved fluorescence (TRF) response of ochratoxin A (OTA)-terbium-DNA aptamer interaction were tested for the quantitative determination of OTA in wheat. Wheat was extracted with acetonitrile/water (60:40, v/v) followed by clean-up through affinity columns containing a DNA-aptamer-based oligosorbent. Then, OTA was detected by TRF spectroscopy after reaction with a terbium fluorescent solution containing the DNA-aptamer probe. The entire procedure was performed in less than 30 min, including sample preparation, and allowed analysis of several samples simultaneously with a 96-well microplate reader. The average recovery from samples spiked with 2.5-25 μg kg(-1) OTA was 77%, with a relative standard deviation lower than 6% and a quantification limit of 0.5 μg kg(-1). Comparative analyses of 29 naturally contaminated (up to 14 μg kg(-1)) wheat samples using the aptamer-affinity column/TRF method or the immunoaffinity column/high-performance liquid chromatography method showed good correlation (r = 0.985) in the range tested. The trueness of the aptamer-based method was additionally assessed by analysis of two quality control wheat materials for OTA. The DNA-ligand system is innovative, simple and rapid, and can be used to screen large quantities of samples for OTA contamination at levels below the EU regulatory limit with analytical performances satisfying EU criteria for method acceptability.