Aptamer-based single-walled carbon nanohorn sensors for ochratoxin A detection

Abstract

Ochratoxin A (OTA), a mycotoxin produced by Aspergillus ochraceus and Penicillium verrucosum, is one of the most significant mycotoxins encountered in foods. In this research, a novel fluorescence biosensing strategy for simple and sensitive OTA detection using an aptamer specific for OTA as recognition element and single-walled carbon nanohorns (SWCNHs) as fluorescence quencher was reported. In the absence of target molecule (OTA), FAM (carboxyfluorescein)-modified aptamer was adsorbed onto the SWCNH surface. In this arrangement, the fluorophore and quencher were in close proximity; thus, FAM fluorescence was readily quenched by fluorescence resonance energy transfer from dye to carbon nanohorn. In the presence of target molecules (OTA), the OTA-specific aptamer form an antiparallel G-quadruplex, which is resistant to being wrapped onto SWCNHs. Therefore, the fluorescence of FAM cannot be quenched, and the fluorescent intensity as a function of OTA concentration was correspondingly measured. We obtained a detection limit of 17.2 nM for our sensing platform based on SWCNHs, with a linear detection range of 20–500 nM. The proposed assay system also exhibited high selectivity for OTA against other mycotoxins. The biosensor was verified for real sample application by testing 1% red wine containing buffer solution spiked with a series of OTA concentrations, and there is a good linear relationship (correlation coefficient = 0.990) between the fluorescence intensity and the logarithm of OTA concentration. Utilization of the proposed biosensor for quantitative determination of mycotoxins in food samples indicated the sensor being a useful tool for verifying the effectiveness of mycotoxin control strategies.