Rapid Determination of Ochratoxin A in Grape and Its Commodities Based on a Label-Free Impedimetric Aptasensor Constructed by Layer-by-Layer Self-Assembly.

Mina Nan,Yang Bi,Guorui Fu,Huali Xue,Lumei Pu,Haitao Long,Sulin Xue

doi:10.3390/toxins11020071

Abstract

A simple and sensitive label-free impedimetric aptasensor for rapid determination of ochratoxin A (OTA) has been developed, which was based on the combination between thiolated aptamer and gold nanoparticles by layer-by-layer self-assembly. Because of the interaction between aptamer and OTA, the relative normalized electron-transfer resistance (ΔRct) values obtained by electrochemical impedance spectroscopy (EIS) was proportional to the concentration of OTA and showed a good linear relationship from 0.1 to 10.0 ng/mL, with a lower detection limit (0.030 ng/mL) than one-step thiolated DNA aptasensor. The established method was successfully applied to detect and analyze OTA in table wine and grape juice, and the recovery was 90.56%–104.21% when PVP effective removed of phenolic substances. The label-free impedimetric aptasensor was used for rapid detection and quantitation of OTA in the inoculated grapes with the Aspergillus Nigri (H1), and the production of OTA (62.4 μg/kg, 20 μg/kg) far exceeded the maximum levels of 2 μg/kg after inoculation for three days. The developed method exhibited a good specificity, high sensitivity, time-efficient, and it could be applied to detect the OTA concentration in grape and its commodities.

Highlights

Grape is one of the world’s largest fruit crops with the highest proportion of processing, such as wine, grape juice, raisins, and other products
A simple method for the formation of aptamer sensors based on layer-by-layer self-assembled was developed in this study
The preparation of the sensor based on the self-assembled monolayer greatly simplified the construction of the sensor

Summary

Introduction

Grape is one of the world’s largest fruit crops with the highest proportion of processing, such as wine, grape juice, raisins, and other products. Grapes are infected by various fungi, which result in the grape decay and mycotoxins contamination [1,2]. Aspergillus and Penicillium are major agents infected grape at the stage of pre-harvest and post-harvest, ochratoxin production occurs during this time and the accumulation of toxins increases rapidly in fruit ripening [3,4,5]. Ochratoxin is a group of important mycotoxins, which mainly contain three important members with similar structures [6,7]. In view of OTA contamination and toxic threat, it is essential to develop a simple and rapid OTA detection method with high selectivity and accuracy

Methods

Results

Conclusion