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Analysis of Mycotoxins in Beer Using a Portable Nanostructured Imaging Surface Plasmon Resonance Biosensor Sweccha Joshi, Rumaisha M Annida, Han Zuilhof, Teris A. van Beek, and Michel W.F. Nielen J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b04106 • Publication Date (Web): 06 Oct 2016 Downloaded from http://pubs.acs.org on October 6, 2016
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Journal of Agricultural and Food Chemistry
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Analysis of Mycotoxins in Beer Using a Portable Nanostructured
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Imaging Surface Plasmon Resonance Biosensor Sweccha Joshi, †, ‡ Rumaisha M. Annida, † Han Zuilhof, † Teris A. van Beek, †* Michel W.F. Nielen†,§
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†
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Wageningen, The Netherlands
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‡
TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
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§
RIKILT Wageningen University & Research, P.O. Box 230, 6700 AE Wageningen, The
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Netherlands
Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE
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*
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[email protected] Corresponding author (Tel:+31 317 482376; Fax: +31 317 484914; E-mail:
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ABSTRACT: A competitive inhibition immunoassay is described for the mycotoxins
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deoxynivalenol (DON) and ochratoxin A (OTA) in beer using a portable nanostructured
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imaging surface plasmon resonance (iSPR) biosensor, also referred to as imaging
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nanoplasmonics. The toxins were directly and covalently immobilized on a 3-dimensional
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carboxymethylated dextran (CMD) layer on a nanostructured iSPR chip. The assay is based
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on competition between the immobilized mycotoxins and free mycotoxins in the solution for
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binding to specific antibodies. The chip surface was regenerated after each cycle and the
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combination of CMD and direct immobilization of toxins allowed the chips to be used for
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more than 450 cycles. The limits of detection (LODs) in beer were 17 ng/mL for DON and 7
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ng/mL for OTA (or 0.09 ng/mL after 75 times enrichment). These LODs allowed detection of
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even less than 10% depletion of the tolerable daily intake of DON and OTA by beer.
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Significant cross-reactivity of anti-DON was observed towards DON-3-glucoside and 3-
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acetyl-DON while no cross-reactivity was seen for 15-acetyl-DON. A preliminary in-house
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validation with 20 different batches of beer showed that both toxins can be detected at the
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considered theoretical safe level for beer. The assay can be used for in-field or at-line
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detection of DON in beer and also in barley without pre-concentration, while OTA in beer
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requires an additional enrichment step thus making the latter in its present form less suitable
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for field applications.
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KEYWORDS: Imaging SPR, mycotoxins, beer, nanoplasmonics, deoxynivalenol, ochratoxin
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Journal of Agricultural and Food Chemistry
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INTRODUCTION
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Mycotoxins are the secondary metabolites of fungi commonly found in several foods,
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beverages, and animal feed and are known to be teratogenic, mutagenic, and carcinogenic.1
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They are carried-over from infected barley into malt and ultimately to beer due to their
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thermal stability and relatively good water solubility.2-4 Therefore, careful screening of beer
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ingredients and end products is required for safety of the consumers. The occurrence of
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different mycotoxins in beer has been reported earlier with most studies focusing on
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deoxynivalenol 1 (DON) mainly due to its high incidence.5,6 Another mycotoxin, ochratoxin
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A 5 (OTA), although detected in beer at low concentrations (only
