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Majer-Baranyi K.,Central Food Research Institute | Szekacs A.,Hungarian Academy of Sciences | Szendro I.,MicroVacuum Ltd. | Kiss A.,Eszterhazy Karoly College | Adanyi N.,Central Food Research Institute
European Food Research and Technology | Year: 2011

Contamination by deoxynivalenol (DON), a trichothecene mycotoxin produced by Fusarium species, occurs in cereals worldwide; therefore, efforts have been made toward the development of rapid and sensitive methods for the detection of this compound. In our investigation, optical waveguide lightmode spectroscopy (OWLS) technique has been applied to label-free detection of DON in both competitive and in direct immunoassay formats using DON-specific polyclonal antibodies. After immobilizing the antibody or the antigen conjugate for the direct or indirect measurement, the sensor chip was used in a flow-injection analyzer system. The direct method was found to result in an unstable sensor response and sensitivity insufficient to determine DON in different grains. In contrast, a competitive immunosensor format provided reproducible quantitative detection in the sub-ppt range. For competitive sensor investigation with the sensitized chip, first the optimal dilution rate of polyclonal antibodies was determined. For the measurements, antibody stock solution was diluted to 8 μg mL-1. During the competitive measurement, standard solutions were mixed with the antibodies at the appropriate concentration, and the mixture was incubated for 1 min and injected into the OWLS system. The sensitive detection range of the competitive detection method was between 0. 01 and 50 ng mL-1. After the establishment of the indirect method, spiked wheat flour samples were investigated. Results obtained with spiked samples showed that OWLS detection has a potential for quick determination of DON in wheat samples. © 2011 Springer-Verlag.


Sugihara K.,ETH Zurich | Delai M.,ETH Zurich | Szendro I.,MicroVacuum Ltd. | Guillaume-Gentil O.,ETH Zurich | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2012

A simultaneous optical waveguide lightmode spectroscopy (OWLS) and electrochemical impedance spectroscopy (EIS) measurement was carried out for the investigation of a supported lipid bilayer and its interactions with a pore-forming peptide, melittin. It was achieved only after the optimization of the ITO coating on the waveguide to increase the electrical sensitivity and the functionalization of the waveguide with a polyelectrolyte to form a lipid bilayer over the ITO surface. The combined system enabled monitoring of melittin pore activities in a wider range of melittin concentrations than either technique alone (1 μg/ml < C melittin < 200 μg/ml). Furthermore, it provided unique information that could not be obtained by the individual methods, such as a better identification of the melittin-pore formation and an insight about the correlation between the total pore area vs. adsorbed amount of melittin. © 2011 Elsevier B.V. All rights reserved.


Adanyi N.,Central Environmental and Food Science Research Institute | Majer-Baranyi K.,Central Environmental and Food Science Research Institute | Nagy A.,Central Environmental and Food Science Research Institute | Nemeth G.,Central Environmental and Food Science Research Institute | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2013

Abstract Label-free, optical waveguide lightmode spectroscopy (OWLS) based immunosensors were developed for vitellogenin (Vtg) determination in carp (Cyprinus carpio). Purified polyclonal serum raised in rabbits against lipovitellin (Lpv) purified from carp ovary and shown to fully cross-react with Vtg was applied both in direct and indirect measurement formats, and analytical features (limit of detection, specificity, matrix effects) were investigated. The direct OWLS immunosensor and the sandwich ELISA assay developed showed linear measuring range in 600-12,000 ng mL?1 and 200-3000 ng mL?1 Lpv concentrations in standard solutions, respectively. The competitive immunosensor allowed a sensitive detection range for Lpv between 3 and 100 ng mL?1. Vtg content in blood and liver samples from male and female carp were determined by indirect OWLS. To reduce the matrix effect, calibration curves were obtained using Vtg-free blood and liver samples from male carp spiked with Lpv. Vtg levels in the liver of female carp was lower than determined in the blood samples, therefore, blood occurs to be a more proper tissue to monitor elevated Vtg in male carp due to possible exposure to water-contaminating endocrine disrupting chemicals. © 2012 Elsevier B.V. All rights reserved.


Majer-Baranyi K.,Food Science Research Institute | Zalan Z.,Food Science Research Institute | Mortl M.,Agro Environmental Research Institute | Juracsek J.,Agro Environmental Research Institute | And 3 more authors.
Food Chemistry | Year: 2016

Optical waveguide lightmode spectroscopy (OWLS) technique has been applied to label-free detection of aflatoxin B1 in a competitive immunoassay format, with the aim to compare the analytical goodness of the developed OWLS immunosenor with HPLC and enzyme-linked immunosorbent assay (ELISA) methods for the detection of aflatoxin in spice paprika matrix. We have also assessed applicability of the QuEChERS method prior to ELISA measurements, and the results were compared to those obtained by traditional solvent extraction followed by immunoaffinity clean-up. The AFB1 content of sixty commercial spice paprika samples from different countries were measured with the developed and optimized OWLS immunosensor. Comparing the results from the indirect immunosensor to that obtained by HPLC or ELISA provided excellent correlation (with regression coefficients above 0.94) indicating that the competitive OWLS immunosensor has a potential for quick determination of aflatoxin B1 in paprika samples. © 2016 Elsevier Ltd.


Adanyi N.,Central Environmental and Food Science Research Institute | Szekacs I.,Hungarian Academy of Sciences | Szendro I.,MicroVacuum Ltd. | Szekacs A.,Central Environmental and Food Science Research Institute
Food and Agricultural Immunology | Year: 2014

An Optical Waveguide Lightmode Spectroscopy (OWLS)-based immunosensor was developed for selective and sensitive determination of histamine content in fermented vegetable juices. The conjugate of the antigen (histamine-bovine serum albumin 10 μg mL-1) was attached on the amino modified sensor surface with glutaraldehyde. During the measurement standard solutions or samples were mixed with antibodies of appropriate concentration (1:1000), the mixture was incubated for 1 minute and injected into the OWLS system. The amount of antibodies bound to immobilised antigen conjugates was inversely proportional to the histamine content. Relative substrate specificity of the antibody was studied, and besides histamine, only putrescine, cadaverine and agmatine were found to give slight sensor responses. Fermented vegetable juice samples treated with different microorganisms were measured in 1000-fold dilution, and analytical data were compared to those measured by HPLC. It was concluded that the method is suitable for the sensitive and selective determination of histamine content. © 2012 Taylor & Francis.

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