A Lateral Flow Immunoassay for the Rapid Detection of Ochratoxin A in Wine and Grape Must

Abstract

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.

Increased sensitivity of lateral flow immunoassay for ochratoxin A through silver enhancement

“…Strips were prepared as previously reported [6], except for the concentration of the OTA-BSA conjugate applied to build the T-line.…”

“…Line intensities were recorded by scanning images (OpticSlim 550 scanner, Plustek Technology GmbH, Norderstedt, Germany). The Scannex 3.0 software (Skannex AS, Hoenefoss, Norway) was used to acquire and process images, as reported [6].…”

“…Wines and grape must samples were treated as reported [6] that is diluted 1:2:2 with NaHCO 3 (0.15M, pH 9.0) and PEG (4% w/v). Grapes musts were also supplemented with 12% (v/v) of absolute ethanol.…”

“…Specifically, silver enhancement was exploited to ameliorate a fully optimized gold-based LFIA for measuring ochratoxin A (OTA) in wine and grape must [6].…”

“…In a preceding work, our group demonstrated the feasibility of using a gold-based LFIA to semi-quantify OTA contamination in wines and grape musts [6]. The assay format was based on the competition between the analyte and a conjugate of OTA immobilized onto the migration membrane (at the Test line) for the binding of antibodies directed toward OTA and labeled with GNPs.…”