RESUMEN

One of the most important tasks in food safety is to properly manage the investigation of mycotoxin contamination in agricultural products and foods made from them, as well as to prevent its occurrence. Monitoring requires a wide range of analytical methods, from expensive analytical procedures with high-tech instrumentation to significantly cheaper biosensor developments or even single-use assays suitable for on-site monitoring. This review provides a summary of the development directions over approximately a decade and a half, grouped according to the biologically sensitive components used. We provide an overview of the use of antibodies, molecularly imprinted polymers, and aptamers, as well as the diversity of biosensors and their applications within the food industry. We also mention the possibility of determining multiple toxins side by side, which would significantly reduce the time required for the analyses.

Asunto(s)

Aptámeros de Nucleótidos , Técnicas Biosensibles , Micotoxinas , Micotoxinas/análisis , Contaminación de Alimentos/análisis , Anticuerpos , Técnicas Biosensibles/métodos

RESUMEN

The herbicide active ingredient glyphosate is the most widely applied herbicidal substance worldwide. Currently it is the market-leading pesticide, and its use is projected to further grow 4.5-fold between 2022 and 2029. Today, glyphosate use exceeds one megaton per year worldwide, which represents a serious environmental burden. A factor in the overall boost in the global use of glyphosate has been the spread of glyphosate-tolerant genetically modified (GM) crops that allow post-emergence applications of the herbicide on these transgenic crops. In turn, cultivation of glyphosate-tolerant GM crops represented 56% of the glyphosate use in 2019. Due to its extremely high application rate, xenobiotic behaviour and a water solubility (11.6 mg/mL at 25 °C) unusually high among pesticide active ingredients, glyphosate has become a ubiquitous water pollutant and a primary drinking water contaminant worldwide, presenting a threat to water quality. The goal of our research was to develop a rapid and sensitive method for detecting this herbicide active ingredient. For this purpose, we applied the novel analytical biosensor technique optical waveguide light-mode spectroscopy (OWLS) to the label-free detection of glyphosate in a competitive immunoassay format using glyphosate-specific polyclonal antibodies. After immobilising the antigen conjugate in the form of a glyphosate conjugated to human serum albumin for indirect measurement, the sensor chip was used in a flow-injection analyser system. For the measurements, an antibody stock solution was diluted to 2.5 µg/mL. During the measurement, standard solutions were mixed with the appropriate concentration of antibodies and incubated for 1 min before injection. The linear detection range and the EC50 value of the competitive detection method were between 0.01 and 100 ng/mL and 0.60 ng/mL, respectively. After investigating the indirect method, we tested the cross-reactivity of the antibody with glyphosate and structurally related compounds.

Asunto(s)

Técnicas Biosensibles , Herbicidas , Plaguicidas , Humanos , Inmunoensayo , Análisis Espectral , Anticuerpos , Productos Agrícolas , Glifosato

RESUMEN

Food security is significantly affected by the mass production of agricultural produce and goods, the growing number of imported foods, and new eating and consumption habits. These changed circumstances bring food safety issues arising from food spoilage to the fore, making food safety control essential. Simple and fast screening methods have been developed to detect pathogens and biomarkers indicating the freshness of food for safety. In addition to the traditional, sequential, chemical analytical and microbiological methods, fast, highly sensitive, automated methods suitable for serial tests have appeared. At the same time, biosensor research is also developing dynamically worldwide, both in terms of the analytes to be determined and the technical toolkit. Consequently, the rapid development of biosensors, including electrochemical-based biosensors, has led to significant advantages in the quantitative detection and screening of food contaminants. These techniques show great specificity for the biomarkers tested and provide adequate analytical accuracy even in complex food matrices. In our review article, we summarize, in separate chapters, the electrochemical biosensors developed for the most important food groups and the food safety issues they can ensure, with particular respect to meat and fish products, milk and dairy products, as well as alcoholic and non-alcoholic beverages.

Asunto(s)

Técnicas Biosensibles , Contaminación de Alimentos , Animales , Contaminación de Alimentos/análisis , Inocuidad de los Alimentos , Técnicas Biosensibles/métodos , Leche , Carne , Técnicas Electroquímicas

RESUMEN

A capillary-based immunofluorescence sensor was developed and incorporated in a flow injection analysis system. The light-guiding capillary was illuminated axially by a 473 nm/5 mW solid state laser through a tailored optofluidic connector. High sensitivity of the system was achieved by efficiently collecting and detecting the non-guided fluorescence signal scattered out along the wall of the capillary. The excitation was highly suppressed with bandpass and dichroic filters by simultaneously exploiting the guiding effect inside the capillary. The glass capillary used as a measuring cell was silanized in liquid phase by 3-aminopropyltriethoxysilane (APTS), and the biomolecules were immobilized using glutaraldehyde inside the capillary. The applicability of the developed system was tested with a bovine serum albumin (BSA)-anti-BSA-IgG model-molecule pair, using a fluorescently labeled secondary antibody. Based on the results of the BSA-anti-BSA experiments, a similar setup using a primary antibody specific for zearalenone (ZON) was established, and a competitive fluorescence measurement system was developed for quantitative determination of ZON. For the measurements, 20 µg/mL ZON-BSA conjugate was immobilized in the capillary, and a 1:2500 dilution of the primary antibody stock solution and a 2 µg/mL secondary antibody solution were set. The developed capillary-based immunosensor allowed a limit of detection (LOD) of 0.003 ng/mL and a limit of quantification (LOQ) of 0.007 ng/mL for ZON in the competitive immunosensor setup, with a dynamic detection range of 0.01-10 ng/mL ZON concentrations.

Asunto(s)

Técnicas Biosensibles , Micotoxinas , Zearalenona , Zearalenona/análisis , Micotoxinas/análisis , Inmunoensayo , Límite de Detección , Anticuerpos , Colorantes

RESUMEN

The Persian walnut (Juglans regia L.) is the most grown nut tree crop in Central Europe. The aim was to study the full Hungarian walnut assortment with a distinct early spring phenology to detect the difference in phenolic profile in their green husks. Furthermore, the relationship between the presence and concentration of phenolic compounds and the tolerance/resistance of the observed cultivars to walnut bacterial blight was investigated. Examining the samples, significant differences were found between the concentrations of the different groups of phenolic compounds. Walnut blight immunity tests were also performed to clarify the role of phenolic compounds in the nut derived from a non-irrigated orchard. The Hungarian-bred local cultivars contained phenolic compounds in higher concentrations than the domesticated ones. There was a significant correlation between the budburst, as well as the pistillate flowers' receptivity and the concentration of juglone. Cultivars with a low concentration of phenolic compounds were the most susceptible to walnut bacterial blight, except 'Bonifác'.

RESUMEN

A digestibility trial was conducted with African catfish hybrid juveniles in order to determine the apparent digestibility coefficients (ADCs) of different nutrients. The experimental diets contained defatted black soldier fly (BSL), yellow mealworm (MW), or fully fat blue bottle fly (BBF) meals, in a 70 : 30 ratio between the control diet and the tested insect meals. The indirect method for the digestibility study was performed using 0.1% yttrium oxide as an inert marker. Fish juveniles of 217.4 ± 9.5 g initial weight were distributed in 1 m3 tanks (75 fish/tank) of a recirculating aquaculture system (RAS), in triplicates, and fed until satiation for 18 days. The average final weight of the fish was 346 ± 35.8 g. The ADCs of the dry matter, protein, lipid, chitin, ash, phosphorus, amino acids, fatty acids, and gross energy for the test ingredients and diets were calculated. A six-month storage test was carried out to evaluate the shelf life of the experimental diets, while the peroxidation and microbiological status of the diets were also assessed. The ADC values of the test diets differed significantly (p < 0.001) compared to those of the control for most of the nutrients. Altogether, the BSL diet was significantly more digestible for protein, fat, ash, and phosphorus than the control diet but less digestible for essential amino acids. Significant differences were found between the ADCs of the different insect meals evaluated (p < 0.001) for practically all nutritional fractions analyzed. The African catfish hybrids were able to digest BSL and BBF more efficiently than MW, and the calculated ADC values agreed with those of other fish species. The lower ADCs of the tested MW meal correlated (p < 0.05) with the markedly higher acid detergent fiber (ADF) levels present in the MW meal and MW diet. Microbiological evaluation of the feeds revealed that mesophilic aerobic bacteria in the BSL feed were 2-3 orders of magnitude more abundant than those in the other diets and their numbers significantly increased during storage. Overall, BSL and BBF proved to be potential feed ingredients for African catfish juveniles and the shelf life of the produced diets with 30% inclusion of insect meal retained the required quality during a six-month period of storage.

RESUMEN

Mycotoxin contamination of cereals used for feed can cause intoxication, especially in farm animals; therefore, efficient analytical tools for the qualitative and quantitative analysis of toxic fungal metabolites in feed are required. Current trends in food/feed analysis are focusing on the application of biosensor technologies that offer fast and highly selective and sensitive detection with minimal sample treatment and reagents required. The article presents an overview of the recent progress of the development of biosensors for deoxynivalenol and zearalenone determination in cereals and feed. Novel biosensitive materials and highly sensitive detection methods applied for the sensors and the application of these sensors to food/feed products, the limit, and the time of detection are discussed.

Asunto(s)

Alimentación Animal , Técnicas Biosensibles , Análisis de los Alimentos/métodos , Contaminación de Alimentos , Tricotecenos/análisis , Zearalenona/análisis , Animales , Grano Comestible , Hongos , Fusarium , Micotoxinas , Control de Calidad

RESUMEN

Project Aquafluosense is designed to develop prototypes for a fluorescence-based instrumentation setup for in situ measurements of several characteristic parameters of water quality. In the scope of the project an enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the detection of several environmental xenobiotics, including mycotoxin zearalenone (ZON). ZON, produced by several plant pathogenic Fusarium species, has recently been identified as an emerging pollutant in surface water, presenting a hazard to aquatic ecosystems. Due to its physico-chemical properties, detection of ZON at low concentrations in surface water is a challenging task. The 96-well microplate-based fluorescence instrument is capable of detecting ZON in the concentration range of 0.09-400 ng/mL. The sensitivity and accuracy of the analytical method has been demonstrated by a comparative assessment with detection by high-performance liquid chromatography and by total internal reflection ellipsometry. The limit of detection of the method, 0.09 ng/mL, falls in the low range compared to the other reported immunoassays, but the main advantage of this ELFIA method is its efficacy in combined in situ applications for determination of various important water quality parameters detectable by induced fluorimerty-e.g., total organic carbon content, algal density or the level of other organic micropollutants detectable by immunofluorimetry. In addition, the immunofluorescence module can readily be expanded to other target analytes if proper antibodies are available for detection.

Asunto(s)

Monitoreo del Ambiente , Ensayo de Inmunoadsorción Enzimática , Técnica del Anticuerpo Fluorescente , Fusarium/metabolismo , Microbiología del Agua , Zearalenona/análisis , Límite de Detección , Reproducibilidad de los Resultados , Espectrometría de Fluorescencia , Calidad del Agua

RESUMEN

Novel optical waveguide lightmode spectroscopy (OWLS)-based immunosensor formats were developed for label-free detection of Fusarium mycotoxin zearalenone (ZON). To achieve low limits of detection (LODs), both immobilised antibody-based (direct) and immobilised antigen-based (competitive) assay setups were applied. Immunoreagents were immobilised on epoxy-, amino-, and carboxyl-functionalised sensor surfaces, and by optimising the immobilisation methods, standard sigmoid curves were obtained in both sensor formats. An outstanding LOD of 0.002 pg/mL was obtained for ZON in the competitive immunosensor setup with a dynamic detection range between 0.01 and 1 pg/mL ZON concentrations, depending on the covalent immobilisation method applied. This corresponds to a five orders of magnitude improvement in detectability of ZON relative to the previously developed enzyme-linked immonosorbent assay (ELISA) method. The selectivity of the immunosensor for ZON was demonstrated with structural analogues (α-zearalenol, α-zearalanol, and ß-zearalanol) and structurally unrelated mycotoxins. The method was found to be applicable in maize extract using acetonitrile as the organic solvent, upon a dilution rate of 1:10,000 in buffer. Thus, the OWLS immunosensor method developed appears to be suitable for the quantitative determination of ZON in aqueous medium. The new technique can widen the range of sensoric detection methods of ZON for surveys in food and environmental safety assessment.

Asunto(s)

Fusarium/metabolismo , Análisis Espectral/métodos , Zearalenona/química , Técnicas Biosensibles , Contaminación de Alimentos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Zea mays/química , Zearalenona/metabolismo

RESUMEN

BACKGROUND: Sprouting is known to improve cereal and pulse nutritional properties. However, several outbreaks of illness have been reported after raw sprout consumption. This research aimed to improve wheat sprout hygienic properties through the use of zinc diacetate. Sprouting conditions (sprouting temperature, soaking time and zinc diacetate solution concentration) were optimized to decrease total plate count, coliforms, and molds and yeasts using a factorial design approach and a desirability function. RESULTS: Based on the responses, the effects of variables were calculated and the interactions between them were determined. Optimal conditions were defined as follows: sprouting temperature 18 °C, soaking time 0.66 h and zinc diacetate concentration 400 mg L-1 . These conditions led to the elimination of coliforms and a decrease in total flora count by 2 log. Interestingly, zinc sprouting increased the zinc content of sprouts and improved their nutritional properties. CONCLUSION: Results showed that the use of zinc solution is a useful tool to improve sprout hygienic and nutritional properties. © 2019 Society of Chemical Industry.

Asunto(s)

Contaminación de Alimentos/prevención & control , Manipulación de Alimentos/métodos , Semillas/crecimiento & desarrollo , Triticum/crecimiento & desarrollo , Zinc/farmacología , Bacterias/crecimiento & desarrollo , Medios de Cultivo/química , Medios de Cultivo/metabolismo , Manipulación de Alimentos/instrumentación , Hongos/crecimiento & desarrollo , Higiene , Valor Nutritivo , Semillas/química , Semillas/microbiología , Triticum/química , Triticum/microbiología , Zinc/análisis

RESUMEN

Mycotoxins, present in a wide range of food and feed commodities, are toxic secondary metabolites produced by a number of different fungi. Certain mycotoxins do not readily degrade at high temperatures, therefore are resistant to food processing, and consequently are present in the human and animal food supply. Optical waveguide lightmode spectroscopy (OWLS) was applied for the detection of aflatoxin B1, in a competitive immunoassay format, to compare the analytical sensitivity achieved with an immunosensor design allowing signal enhancement by increasing the sensor surface through immobilization of gold nanoparticles (AuNPs) of different size and origin (obtained by chemical or biotechnological synthesis). The effects of AuNPs median size, the methods of sensitization and the biochemical parameters on immunosensor performace were examined. After optimization of the sensitized sensor surface, an immunosensing method was developed for the analysis of aflatoxin in paprika matrix and the results were compared with HPLC reference measurements.

Asunto(s)

Oro/química , Nanopartículas del Metal/química , Micotoxinas/análisis , Refractometría/métodos , Aflatoxina B1/análisis , Capsicum/metabolismo , Cromatografía Líquida de Alta Presión , Contaminación de Alimentos/análisis , Concentración de Iones de Hidrógeno , Láseres de Gas , Tamaño de la Partícula , Albúmina Sérica Bovina/química

RESUMEN

BACKGROUND: In soybean, at least 16 seed proteins have been identified as causing allergenic reactions in sensitive individuals. As a soybean genebank accession low in the immunodominant protein P34 (Gly m Bd 30K) has recently been found, introgression of the low-P34 trait into adapted soybean germplasm has been attempted in order to improve the safety of food products containing soybean protein. Therefore, marker-assisted selection and proteomics were applied to identify and characterize low-P34 soybeans. RESULTS: In low-P34 lines selected from a cross-population, concentrations of the P34 protein as identified with a polyclonal antibody were reduced by 50-70% as compared to P34-containing controls. Using 2D electrophoresis and immunoblotting, the reduction of P34 protein was verified in low-P34 lines. This result was confirmed by liquid chromatographic-tandem mass spectrometric analysis, which revealed either a reduction or complete absence of the authentic P34 protein as suggested from presence or absence of a unique peptide useful for discriminating between conventional and low-P34 lines. CONCLUSION: Marker-assisted selection proved useful for identifying low-P34 soybean lines for the development of hypoallergenic soy foods. The status of the P34 protein in low-P34 lines needs further characterization. In addition, the food safety relevance of low-P34 soybeans should be tested in clinical studies. © 2016 Society of Chemical Industry.

Asunto(s)

Antígenos de Plantas/efectos adversos , Cruzamientos Genéticos , Regulación hacia Abajo , Glycine max/química , Fitomejoramiento , Semillas/química , Alimentos de Soja/análisis , Proteínas de Soja/efectos adversos , Antígenos de Plantas/genética , Antígenos de Plantas/metabolismo , Ensayo de Inmunoadsorción Enzimática , Sistemas Especialistas , Hipersensibilidad a los Alimentos/dietoterapia , Hipersensibilidad a los Alimentos/prevención & control , Inocuidad de los Alimentos , Alimentos Funcionales/efectos adversos , Alimentos Funcionales/análisis , Regulación de la Expresión Génica de las Plantas , Ligamiento Genético , Marcadores Genéticos , Humanos , Repeticiones de Microsatélite , Proteómica/métodos , Semillas/efectos adversos , Semillas/crecimiento & desarrollo , Semillas/metabolismo , Selección Genética , Alimentos de Soja/efectos adversos , Proteínas de Soja/genética , Proteínas de Soja/metabolismo , Glycine max/efectos adversos , Glycine max/crecimiento & desarrollo , Glycine max/metabolismo

RESUMEN

A novel biosensor for l-ascorbic acid determination in different beverages was elaborated. The ascorbate oxidase enzyme (AAO) from Cucurbita sp., EC 1.10.3.3, was immobilized on a screen-printed carbon electrode with poly(ethylene glycol) (400) diglycidyl ether (PEGDGE) as a crosslinking agent. The standards and samples were measured first with a blank electrode. An inert protein, bovine serum albumin (BSA), was immobilized on the surface of this electrode with PEGDGE. The BSA mass was equivalent to the mass of 10 U of AAO enzyme immobilized on the electrodes (0.021 mg). The linear measuring range for l-ascorbic acid was between 5 and 150 µmol/L. As l-ascorbic acid is a vital vitamin and a common antioxidant used in food industry, fruit juices and vitamin C effervescent tablets were examined. The results were compared to HPLC measurements.

RESUMEN

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.

Asunto(s)

Aflatoxina B1/química , Capsicum/química , Cromatografía Líquida de Alta Presión/métodos , Ensayo de Inmunoadsorción Enzimática/métodos , Inmunoensayo/métodos , Análisis Espectral/métodos , Especias/análisis , Aflatoxina B1/análisis

RESUMEN

The regular consumption of foods containing probiotic bacteria has beneficial physiological effects on the health and the digestion system. There is a need for novel analytical approaches for the determination of these bacteria that are faster than the classical plate counting method. For this purpose, two label-free biosensors were investigated and presented in this paper: Quartz Crystal Microbalance (QCM) and Optical Waveguide Lightmode Spectroscopy (OWLS) based direct immunosensors were developed for real-time direct detection of probiotic bacteria in fermented dairy products. Bifidobacterium bifidum O1356 and Lactobacillus acidophilus O1132 were detected by polyclonal anti-B. bifidum IgG and anti-L. acidophilus IgG immobilized on the sensors' surface. Sulfo-LC-SPDP cross linking agent was used to bind antibodies to the gold surface of the QCM's AT-cut quartz wafer. Concerning OWLS, antibodies were covalently bound to the amino groups of the silanized surface of the waveguide by glutaraldehyde. The dynamic measuring range was found between 1.0E+3 and 5.0E+5CFUmL(-1) in 100 fold diluted fermented milk products by QCM and with OWLS. Considering the current legislation of the probiotic content in probiotic products, the two developed immunosensors can be applied for rapid quantification of L. acidophilus and B. bifidum in fermented milk. These examinations offer effective alternatives to the microbiological plate counting method.

Asunto(s)

Productos Biológicos , Técnicas Biosensibles/métodos , Productos Lácteos/microbiología , Análisis de los Alimentos/métodos , Microbiología de Alimentos/métodos , Lactobacillus acidophilus , Probióticos/análisis , Anticuerpos Antibacterianos/química , Técnicas Biosensibles/instrumentación , Análisis de los Alimentos/instrumentación , Microbiología de Alimentos/instrumentación , Inmunoglobulina G/química , Análisis Espectral/instrumentación , Análisis Espectral/métodos

RESUMEN

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.

Asunto(s)

Técnicas Biosensibles/métodos , Catepsinas/química , Escherichia coli , Dióxido de Silicio/química , Antibacterianos/análisis , Antibacterianos/química , Carbofurano/análisis , Carbofurano/química , Catepsinas/genética , Catepsinas/metabolismo , Cloranfenicol/análisis , Cloranfenicol/química , Escherichia coli/citología , Escherichia coli/metabolismo , Peróxido de Hidrógeno/análisis , Peróxido de Hidrógeno/farmacología , Insecticidas/análisis , Insecticidas/química , Oxidantes/química , Estrés Oxidativo/efectos de los fármacos , Penicilina G/análisis , Penicilina G/química

RESUMEN

The novel putrescine oxidase based amperometric biosensor selectively measures putrescine, which can be considered as an indicator of microbial spoilage. Putrescine oxidase (PUOX, EC 1.4.3.10) was isolated from Kocuria rosea (Micrococcus rubens) by an improved and simplified purification process. Cells were grown on brain heart infusion medium supplemented with putrescine. Cell-free extract was prepared in Tris buffer (pH 8.0) by Bead-beater. A newly elaborated step based on three-phase partitioning (TPP) was applied in the purification protocol of PUOX. The purified enzyme was immobilized on the surface of a spectroscopic graphite electrode in redox hydrogel with horseradish peroxidase, Os mediator and poly(ethylene glycol) (400) diglycidyl ether (PEGDGE) as crosslinking agent. This modified working electrode was used in wall-jet type amperometric cell together with the Ag/AgCl (0.1M KCl) reference electrode and a platinum wire as auxiliary electrode in flow injection analysis system (FIA). Hydrogel composition, pH and potential dependence were studied. Optimal working conditions were 0.45 mLmin(-1) flow rate of phosphate buffer (66 mM, pH 8.0) and +50 mV polarizing potential vs. Ag/AgCl. The linear measuring range of the method was 0.01-0.25 mM putrescine, while the detection limit was 5 µM. Beer samples were investigated by the putrescine biosensor and the results were compared by those of HPLC reference method.

Asunto(s)

Cerveza/análisis , Técnicas Biosensibles/métodos , Biotecnología/métodos , Micrococcus/enzimología , Oxidorreductasas actuantes sobre Donantes de Grupo CH-NH/aislamiento & purificación , Putrescina/metabolismo , Carbono , Medios de Cultivo , Electrodos , Micrococcus/clasificación , Micrococcus/crecimiento & desarrollo , Oxidorreductasas actuantes sobre Donantes de Grupo CH-NH/metabolismo , Putrescina/análisis , Control de Calidad

RESUMEN

An amperometric detector and an enzymatic reaction were combined for the measurement of L-ascorbic acid. The enzyme cell (containing immobilized ascorbate oxidase) was connected to a flow injection analyzer (FIA) system with a glassy carbon electrode as an amperometric detector. During optimization and measurements two sample injectors were used, one before and one after the enzyme cell, thus eliminating the background interferences. Subtraction of the signal area given in the presence of enzyme from the one given in the absence of enzyme was applied for measuring analyte concentrations and calibration at 400 mV. Analysis capacity of system is 25 samples/hour. The relative standard deviation (RSD) was below 5% (5 times repeated, 400 µmol/L conc.), linearity up to 400 µmol/L, limit of detection (LOD) 5 µmol/L, fitting of calibration curve in 25-400 µmol/L range was R (2) = 0.99.

Asunto(s)

Ácido Ascórbico/análisis , Análisis de Inyección de Flujo/instrumentación , Análisis de los Alimentos/instrumentación , Ascorbato Oxidasa/química , Catálisis , Electroquímica , Enzimas Inmovilizadas/química , Límite de Detección , Reproducibilidad de los Resultados

RESUMEN

Coupling the high specificity of the immunoanalytical reaction with the high sensitivity of optical waveguide light-mode spectroscopy (OWLS) detection gives the possibility to develop immunosensors with in most cases a definitely lower detection limit than traditionally used immunoassays. Measurements were performed on the sensitized surface of optical waveguide grating coupler sensors (2400 lines/mm grating). The OWLS technique is based on the precise measurement of the resonance angle of a polarized laser light (632.8 nm), diffracted by a grating and incoupled into a thin waveguide. The effective refractive index, determined from the resonance incoupling angle detected at high accuracy, allows determination of layer thickness and coverage (or mass) of the adsorbed or bound material with ultrahigh sensitivity. OWLS immunosensors were developed as label-free immunosensors with an amino group modified SiO(2)-TiO(2) sensor surface on which the immunoreactants could be anchored. One of the components of the antibody-antigen complex was chemically bound on the sensor surface, allowing noncompetitive or competitive detection of the analytes. To illustrate that the resulting immunosensors are suitable for the determination of small and large molecular weight analytes, OWLS sensor formats were applied for quantitative detection of a herbicide active ingredient trifluralin, a Fusarium mycotoxin zearalenone, and an egg yolk protein of key importance in endocrine regulation, vitellogenin.

Asunto(s)

Monitoreo del Ambiente/instrumentación , Contaminantes Ambientales/análisis , Inmunoensayo/instrumentación , Dispositivos Ópticos , Refractometría/instrumentación , Análisis Espectral/instrumentación , Bioensayo/instrumentación , Monitoreo del Ambiente/métodos , Diseño de Equipo , Análisis de Falla de Equipo , Reproducibilidad de los Resultados , Sensibilidad y Especificidad

RESUMEN

Selenium is an essential trace element and a component of various enzymes with antioxidant functions. High-sensitive C-reactive protein (hsCRP) is an early indicator of increased lipid peroxidation. The serum selenium concentration, lipid parameters, and hsCRP values of gestational diabetic pregnant women (GD), control pregnant women (CP), and healthy nonpregnant controls (HC) were compared. Blood was taken between the 24th and the 28th week of pregnancy when the oral glucose tolerance test was performed. Selenium concentration was determined by atomic absorption spectrometry after hydride generation. HsCRP was measured by immunturbidimetry. HC had significantly higher serum selenium concentrations than GD and CP women (HC = 77.4 +/- 14.82, GD = 51.7 +/- 11.62, and CP = 40.5 +/- 8.03 microg/l, respectively). HsCRP values of both GD and nondiabetic pregnant women were significantly higher compared to controls. Significant negative correlations were found between serum selenium and total cholesterol, low-density lipoprotein cholesterol, and hsCRP values indicating that low selenium levels are associated with increased lipid peroxidation. Serum selenium concentrations of Hungarian pregnant women are low compared to internationally published data.

Asunto(s)

Proteína C-Reactiva/metabolismo , Diabetes Gestacional/sangre , Segundo Trimestre del Embarazo/sangre , Selenio/sangre , Adulto , Glucemia/metabolismo , Femenino , Humanos , Hungría , Peroxidación de Lípido , Embarazo/sangre