Abstract
Ochratoxin A (OTA) is a type of mycotoxin generated from the metabolism of Aspergillus and Penicillium, and is extremely toxic to humans, livestock, and poultry. However, traditional assays for the detection of OTA are expensive and complicated. Other than OTA aptamer, OTA itself at high concentration can also adsorb on the surface of gold nanoparticles (AuNPs), and further inhibit AuNPs salt aggregation. We herein report a new OTA assay by applying the localized surface plasmon resonance effect of AuNPs and their aggregates. The result obtained from only one single linear calibration curve is not reliable, and so we developed a “double calibration curve” method to address this issue and widen the OTA detection range. A number of other analytes were also examined, and the structural properties of analytes that bind with the AuNPs were further discussed. We found that various considerations must be taken into account in the detection of these analytes when applying AuNP aggregation-based methods due to their different binding strengths.
Highlights
The ochratoxins constitute a group of structurally similar mycotoxins that are produced mainly by the metabolism of Aspergillus and Penicillium (Kuiper-Goodman and Scott, 1989; Malir et al, 2016)
The adsorb on the surface of gold nanoparticles (AuNPs) prepared from the reaction of HAuCl4 with sodium citrate can be stably dispersed in pure water due to the charge repulsion from the surface carboxyl groups, which leads to the formation of a dark red colloidal liquid with a UV-vis wavelength absorbance maximum at ∼520 nm
As DNA can adsorb on the AuNP surfaces through interactions of their base groups with gold (Demers et al, 2002), which is even stronger than DNA hybridization (Demers et al, 2002; Kimura-Suda et al, 2003; Sponer et al, 2004), DNA molecules can protect the AuNPs from salt aggregation (Liu and Liu, 2017)
Summary
The ochratoxins constitute a group of structurally similar mycotoxins that are produced mainly by the metabolism of Aspergillus and Penicillium (Kuiper-Goodman and Scott, 1989; Malir et al, 2016). Since the first report into the quantitative detection of OTA was published in 1973 (Nesheim et al, 1973), a number of additional OTA detection methods have been developed based on thin-layer chromatography (Nesheim et al, 1973), high performance liquid chromatography (HPLC) (Molinié et al, 2005), gas chromatography (Jiao et al, 1992), and mass spectrometry (Ediage et al, 2012; Cramer et al, 2015) These methods offer satisfactory sensitivity and selectivity, they tend to require expensive instrumentation, complicated operations, and highly-trained operators. To obtain reliable results and widen the OTA detection range, a “double calibration curve” method will be examined to produce a label-free, rapid, and cost-competitive method
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