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Majer-Baranyi K.,Central Food Research Institute | Szekacs A.,Hungarian Academy of Sciences | Szendro I.,MicroVacuum Ltd | Kiss A.,Eszterházy Károly 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.


Adanyi N.,Central Environmental and Food Science Research Institute | Bori Z.,Central Environmental and Food Science Research Institute | Szendro I.,MicroVacuum Ltd. | Erdelyi K.,MicroVacuum Ltd. | And 5 more authors.
New Biotechnology | Year: 2013

In the last years, a new group of enzymes, the so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of not only amorphous silica among others. These enzymes are able to catalyze the polycondensation and deposition of silica at mild conditions. Silicateins can be expressed in Escherichia coli. The recombinant proteins are expressed on the surface of the cell wall and are able to catalyze the formation of a polysilicate net around the bacterial cells providing the possibility for further attachment to the surface of SiO2 containing sensor chips. With this mild immobilization process it is now possible to prepare novel microbial sensors based on Optical Waveguide Lightmode Spectroscopy.In the present study, the immobilization of silicatein modified E. coli BL21AI cells onto the SiO2-type chips was optimized (buffer concentration, pH, temperature, reaction time, and so on) and then the biological properties, in particular the inhibitory effect of stressors/environmental pollutants on the novel bacterial sensor were studied in real time.The effect of oxidative stress was investigated by exposing the sensors containing biosilica-immobilized E. coli BL21AI cells to various concentrations of hydrogen peroxide. The effect of antibiotics was tested using chloramphenicol (CAP) which is effective against a variety of Gram-positive and Gram-negative bacteria and penicillin G which destroys the bacterial cell wall. In addition, the inhibition by carbofuran (CF) pesticide was also tested. CF is a highly toxic compound which inhibits cholinesterase activity. According our results we can conclude that the novel bacterial sensor consisting of the silicatein modified E. coli BL21AI cells immobilized on OWLS sensor surface could be an effective tool to detect the presence of different type of pollutants in real time measurement. However penicillin G and CF are not specifically inhibitors of E. coli strain, but some inhibitory effect could be still determined beside the well expressed signals for H2O2 and CAP obtained with the novel microbial sensor. © 2013 Elsevier B.V.


Adanyi N.,Central Environmental and Food Science Research Institute | Bori Z.,Central Environmental and Food Science Research Institute | Szendro I.,MicroVacuum Ltd. | Erdelyi K.,MicroVacuum Ltd. | And 5 more authors.
Sensors and Actuators, B: Chemical | Year: 2013

In the last years, a new group of enzymes, so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of amorphous silica. Silicateins are able to catalyze the polycondensation and deposition of silica at mild conditions (low temperature and physiological pH). By means of these enzymes it is possible for the first time to produce silica nanostructures biocatalytically, which opens new ways for construction of biosensors. The cDNAs encoding the responsible enzymes have been isolated and the proteins can be produced in a recombinant way. Here we demonstrate the silicatein-mediated biosilica formation on the surface of SiO2 sensors in model measurements using Optical Waveguide Lightmode Spectroscopy (OWLS) for real-time evaluation. The efficiency of the enzyme reaction on the surface of the SiO2 chips was studied and the parameters of this process were optimized. Silicatein can be expressed in Escherichia coli and the resulting recombinant protein is able to catalyze the formation of silica shell around the bacterial cells. The described immobilization strategy provides a novel technology for the development of microbial biosensors. © 2012 Elsevier B.V. All rights reserved.


Majer-Baranyi K.,Food Science Research Institute | Adanyi N.,Food Science Research Institute | Nagy A.,Food Science Research Institute | Bukovskaya O.,DoubleDelta Kft. | And 2 more authors.
International Journal of Environmental Analytical Chemistry | Year: 2015

A label-free, optical waveguide lightmode spectroscopy based immunosensor was developed for frog (Bombina orientalis) vitellogenin (Vtg) determination in biological samples as a biomarker for exogenous oestrogen compounds. Antibody against Vtg was produced in rabbits immunised with purified lipovitellin (Lpv), a precursor of Vtg, from the homogenised ovary of oriental fire-bellied toads (B. orientalis). The purified protein and Lpv/Vtg-specific serum were applied in both competitive and direct immunoassay formats using optical waveguide lightmode spectroscopy immunosensor. When measuring Vtg in direct manner, the Lpv antibody (1.76 µg mL−1) was immobilised on the sensor surface, and the linear measuring range for Vtg was 0.1–10 µg mL−1. During the competitive measurement, 100 ng mL−1 Lpv was applied for the immobilisation. The linear measuring range for Vtg was 0.5–50 ng mL−1. We studied the relative substrate specificity of the antibody, and it was concluded that the method is suitable for the sensitive and selective determination of Vtg levels in toads. Heart, liver and gonad samples from male animals were spiked with Vtg and were analysed using the newly developed method, and female toads and spawn samples were tested and compared to the calibration curve obtained by the spiked samples. © 2015 Taylor & Francis.


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.


PubMed | Agro Environmental Research Institute, MicroVacuum Ltd. and Food Science Research Institute
Type: | Journal: 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.


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.


Szekacs I.,Hungarian Academy of Sciences | Kaszas N.,Semmelweis University | Grof P.,Semmelweis University | Erdelyi K.,MicroVacuum Ltd. | And 5 more authors.
PLoS ONE | Year: 2013

Optical waveguide lightmode spectroscopic (OWLS) techniques were probed for monitoring ion permeation through channels incorporated into artificial lipid environment. A novel sensor set-up was developed by depositing liposomes or cell-derived membrane fragments onto hydrophilic polytetrafluoroethylene (PTFE) membrane. The fibrous material of PTFE membrane could entrap lipoid vesicles and the water-filled pores provided environment for the hydrophilic domains of lipid-embedded proteins. The sensor surface was kept clean from the lipid holder PTFE membrane by a water- and ion-permeable polyethylene terephthalate (PET) mesh. The sensor set-up was tested with egg yolk lecithin liposomes containing gramicidin ion channels and with cell-derived membrane fragments enriched in GABA-gated anion channels. The method allowed monitoring the move of Na + and organic cations through gramicidin channels and detecting the Cl-- channel functions of the (α5β 2γ2) GABAA receptor in the presence or absence of GABA and the competitive GABA-blocker bicuculline. © 2013 Székács et al.


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.


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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