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PubMedDate not supplied

Vitamin and pseudovitamin analysis with biosensors in food products--a review.

Biosensors are becoming increasingly important in the food industry for application in safety and quality control among routinely used techniques such as microbiology, chromatography, or specific enzymatic methods. Biosensors offer advantages as alternatives to conventional methods because of their inherent specificity, simplicity, and rapid response. This article presents a short review of vitamin and pseudovitamin analysis techniques using biosensor technology as applied in the food industries, with particular attention to immobilization techniques of biorecognition elements, transducers, an overview of vitamin biosensors, and some future trends.

Biosensing Techniques↗

PubMedDate not supplied

Spreeta-based biosensor immunoassays to detect fraudulent adulteration in milk and milk powder.

Biacore biosensors (Biacore AB, Uppsala, Sweden) have proven to be robust analytical tools for the automated immunochemical detection of different adulterants and contaminants in milk and milk powder. However, the significant cost of the instruments is a disincentive for their wide application in food control laboratories. Therefore, a low-cost alternative optical biosensor (Spreeta, Texas Instruments, Attleboro, MA) was built into an affordable liquid handling system. Using this prototype biosensor, an inhibition immunoassay for bovine K-casein was evaluated for the detection of cow's milk in ewe's and goat's milk and for the detection of bovine rennet whey powder in milk powder. Comparable sensitivities were obtained for both adulterants in the Spreeta-based prototype biosensor and a Biacore 3000 instrument. The limit of detection for cow's milk was 0.17% (v/v) and bovine rennet whey powder could be detected in milk powder above 1% (w/w). The Spreeta sensor was also useful in the control of fraudulent water additions to milk, simply by measuring differences in the bulk response.

Animals↗

PubMed2006

[Flow injection biosensor based on the immobilized AChE].

A biosensor based on the flow injection system was constructed with the immobilized AChE from Scomberomorus niphonius (Curier) as identification element and a pH electrode as transducer. When phosphate buffer was used as carrier liquid, a good reproducibility (RSD = 1.427% , n=10) of the biosensor response was obtained after the substrate was injected repetitively. After an incubation time of 20 min, the calibration graph to methyl-parathion is linear (r = 0.9986) when its concentration ranges from 4.29 x 10(-10) mol x L(-1) to 4.29 x 10(-8) mol x L(-1) , and the detection limit is 1.3 x 10(-10) mol x L(-1). However, the sensitivity of this biosensor to methyl-parathion when using clean seawater as carrier liquid is not as good as that using phosphate buffer. But after preoxidation of methyl-parathion with NaClO as oxidant, the detection limit of the biosensor to methyl-parathion in seawater can be improve to 2.16 x 10(-7) mol x L(-1).

Acetylcholinesterase↗

PubMedDate not supplied

Biosensors and the clinical laboratory.

Aside from the economic factors that make biosensors attractive, on-board signal conditioning and signal processing improve the limits of detection and simplify use of the devices. The present discussion summarizes the breadth of biosensor design and application, and the requirements of clinical assay detection. Current sensor research is aimed toward extending the lower limits of detection for nonradioactive immunoassays. The clinical laboratory is in a state of change; operating and instrumentation costs will affect the delivery of diagnostics. Technology will assume a major role in reshaping the clinical laboratory. Biosensors promise to deliver the diagnostic tools for the evolution that is now in progress. The clinical laboratory will no doubt continue to perform chemical profiling and the more specialized tests. The successful implementation of solid-state sensor technology promises to simplify immunoassay procedures, as the autoanalyzer did some 20 years ago for the profiling of blood metabolites. It is likely that more tests will be performed in physicians' offices with the advent of highly automated and cost-effective biosensors. By the use of this technology, practitioners of critical care medicine will be able to assume greater responsibility for diagnostic testing.

Clinical Laboratory Techniques↗

PubMedDate not supplied

Conductometric biosensor for ethanol detection based on whole yeast cells.

The quantification of ethanol in alcoholic beverages was performed by yeast cell-based conductometric biosensor. A membrane with yeast cells immobilized in 2% Ca-alginate gel was attached on gold planar electrodes. Changes in conductivity due to the specific consumption of ethanol by yeast cells were registered by the computer-controlled sensor system. The response time of the constructed microbial sensor was less than 5 min, linearity (in a logarithmic scale) was observed in the range of 5-100 mM alcohol concentration. It was established that pH value in their region from 5 to 8 did not influence the levels of initial signal. The increase of a buffer capacity in the sample results in the decrease of the biosensor output. The minimal detectable level of ethanol was 1 mM and the relative standard deviation appeared to be 10-12% for 15 repeated assays. When the system was operated and stored at 20-25 degrees C, the biosensor response was stable for only 3 days. However, when the microbial sensor was stored at 4 degrees C, the system was stable up to 12 days. Good correlation between the results obtained by a conductometric cell-biosensor and gas chromatograph was observed.

Alcoholic Beverages↗

PubMed1994

A genetically engineered, protein-based optical biosensor of myosin II regulatory light chain phosphorylation.

Myosin II is an important motor in the contraction of smooth and striated muscle as well as in a variety of non-muscle cell motile events including cytokinesis, cortical contractions during migration of fibroblasts, and capping of receptors. Phosphorylation of the 20-kDa light chain by myosin light chain kinase is part of the regulation of smooth muscle and mammalian nonmuscle myosin II. We designed, characterized, and tested the use of a protein-based optical biosensor to monitor this phosphorylation "switch." A regulatory light chain was genetically engineered to contain a single cysteine at amino acid position 18. The mutant light chain (Cys18.LC20), reacted with the fluorophore acrylodan, responded to phosphorylation of serine 19 with a fluorescence emission quenching of 60% and a 28-nm red-shift. When the acrylodan-labeled mutant light chain (AC-Cys18.LC20) was exchanged into turkey gizzard myosin II, it exhibited a 25% fluorescence emission quenching and a 10-nm red-shift upon phosphorylation of serine 19. The myosin II optical biosensor exhibited nearly control levels of the rate of phosphorylation, K+ATPase activity, and in vitro motility. The acrylodan-labeled light chain was exchanged into the A-bands of chicken pectoralis myofibrils in situ to demonstrate the localization and activity of the biosensor in a highly ordered contractile system. Fluorometry and quantitative fluorescence microscopic imaging experiments demonstrated that AC-Cys18.LC20 exchanged myofibrils expressed a phosphorylation-dependent fluorescence change. Labeled light chains were also incorporated into stress fibers of living fibroblasts and smooth muscle cells. This general approach of combining molecular biology and fluorescence spectroscopy to create novel protein-based optical biosensors should provide valuable tools for investigations with model systems and solution studies and ultimately yield important information about temporal-spatial chemical and molecular changes in live cells.

2-Naphthylamine↗

PubMed1996

Robust, reliable biosensor for continuous monitoring of urea during dialysis.

We developed a new urea sensor for the on-line monitoring of hemodialysis adequacy. The biosensor consisted of an immobilized urease cartridge placed between magnetoinductive conductivity cells. The biosensor output was taken as the conductivity difference between these cells. The device was placed on the ultrafiltrate line of a paired filtration dialysis system. The amount of urease present in the cartridge was sufficient for the complete conversion to ammonium carbonate of urea up to 35 mmol/L. Agreement was good between the urea concentration by the biosensor method and an automated analyzer for seven patients: range 8.07-30.3 mmol/L (22.6-84.8 mg/dL blood urea nitrogen, BUN); intercept 0.20 +/- 0.1 mmol/L (0.55 +/- 0.4 mg/dL BUN); slope 1.01 +/- 0.01; r 0.997; S(y/x) 0.40 mmol/L (1.11 mg/dL BUN). The device proposed meets the requirements of accuracy, cost, ruggedness, and ease of use (no calibration required) for a biosensor to be used for continuous monitoring of hemodialysis.

Animals↗

PubMed1999

Analysis of analyte-receptor binding kinetics for biosensor applications: an overview of the influence of the fractal dimension on the surface on the binding rate coefficient.

An overview of fractal analysis is presented for analyte-receptor binding kinetics for different types of biosensor application. Data taken from the literature can be modelled by using (1) a single-fractal analysis, (2) a single- and a dual-fractal analysis, and (3) a dual-fractal analysis. Cases (2) and (3) represent a change in the binding mechanism as the reaction progresses on the surface. Predictive relationships developed for the binding rate coefficient as a function of the analyte concentration are of particular value because they provide a means by which the binding rate coefficients can be manipulated. Relationships are presented for the binding rate coefficients as a function of the fractal dimension, Df, or the degree of heterogeneity that exists on the surface. The binding rate coefficient is rather sensitive to the degree of heterogeneity, Df, that exists on the biosensor surface. For the examples analysed, the order of dependence of the binding rate coefficient on Df ranges from 1.4770 (k1), for the binding of intercalators and metabolites in solution to DNA immobilized at a positively charged surface, to 4.9434 for the binding of 5 nM nucleotide+GroEL in solution to GroES immobilized on a Ni2+-nitriloacetic acid sensor chip [Nieba, Nieba-Axmann, Persson, Hamalainen, Edebratt, Hansson, Lidholm, Magnusson, Karlsson and Pluckhun (1997) Anal. Biochem. 252, 217-228]. GroEl and GroES are two proteins (chaperones) which facilitate protein folding in the cell in an ATP-dependent manner [Hemmingson, Woolford, van der Vies, Tilly, Dennis, Georgopoulos, Henfrix and Ellis (1988) Nature (London) 333, 330-334]. The overview provides an overall analysis of the reaction parameters of importance observed and how they are influenced in antigen-antibody-binding kinetics for different biosensor applications. The predictive relationships presented provide further physical insights into the binding reactions on the surface, and should assist in enhancing biosensor performance. In general, the technique and the overview presented are applicable for the most part to other reactions occurring on different types of surface, for example cell-surface reactions.

Antigen-Antibody Reactions↗

PubMed1993

Frey's syndrome analysis with biosensor. A preliminary study.

OBJECTIVE: Objective quantification of Frey's syndrome (gustatory sweating), following total parotidectomy. A biosensoring method of enzymatic electrodes enabling the detection of L-lactate on intact skin with the use of a skin extraction device and enzymatic electrodes is presented and analyzed. DESIGN: A criterion standard study. SETTING: This prospective trial was undertaken at our research laboratory (University of Paris [France]). Parotidectomy was performed in our department, which is a tertiary care center for parotid gland pathology. PATIENTS: Twenty-eight patients with gustatory sweating following total parotidectomy and nine control patients not operated on were asked to take part in this prospective study. MAIN OUTCOME AND MEASURES: Gustatory sweating was assessed in all patients using a clinical scale, the Minor starch iodine test, and the L-lactate biosensoring method. RESULTS: Instrumentation and assay procedure for the L-lactate biosensoring method are detailed. Statistical analysis of data was performed using the Kruskal-Wallis H Test and the Mann-Whitney U Test. Results demonstrate that this method enables objective measurement of the L-lactate on skin without the need for chemical reagents, continuous nondestructive analysis in real time, and physiological dynamic monitoring of the L-lactate rate of production after stimulus. Data achieved strongly suggested that the aberrant regeneration theory is the main clue to Frey's syndrome pathogenesis. CONCLUSION: This safe, reliable, noninvasive, objective, and highly sensitive method provides an investigative tool for clinicians as well as physiologists involved with patients presenting gustatory sweating following parotid gland surgery.

Adenoma, Pleomorphic↗

PubMed1999

Mixed-valence compound-based biosensor.

A cobalt(II)hexacyanoferrate-based biosensor has been prepared simply by codeposition of an enzyme, together with the electrochemical formation of a cobalt (II)hexacyanoferrate compound electrochemically. The compound can be generated at a constant potential of -0.05 V (vs. Ag/AgCl). This compound possesses the catalytic property of reducing hydrogen peroxide to water at the operating potential of 0.0 V vs. Ag/AgCl. The mixed-valence compound-based biosensor possesses an unique interference-independent feature, which is important for biomedical application; this feature is attributed to the low overvoltage characteristic of cobalt (II)hexacyanoferrate. The electrochemical glucose biosensor responds to a series of glucose injections with linearity up to 5 mM (with correlation coefficient R = 0.9999) and the sensitivity of the linear portion is 733 nA/(cm2 x mM). The detection limit is 2 x 10(-6)M (S/N = 3). Both the potential-dependent electron transfer rate constant and the apparent Michaelis-Menten constant were studied in rotating disk experiments. The apparent Michaelis-Menten constant, Km' calculated from the slope of the "Lineweaver-Burke" type reciprocal plot is 28 mM. A fast-response characteristic is observed in the rotating disk experiment and the 95% response time is 14.5 sec. No response was observed from the addition of either 2 x 10(-4)M galactose, acetaminophen, ascorbic acid, uric acid, cysteine, tyrosine, dopamine, or 1,4-dihydroxyquinone in the absence and/or in the presence of 5 x 10(-4)M glucose.

Biosensing Techniques↗

PubMedDate not supplied

Principles and applications of flow injection analysis in biosensors.

In practical applications biosensors are often forced to operate under less than optimal conditions. Because of their construction, and the physical processes and chemical reactions involved in their operation, compromise conditions are frequently required to synchronize all events taking place. Therefore, and in order to implement functions such as periodic calibration, conditioning and possible regeneration of the biosensor, and, very importantly, to yield the freedom to select the optimum detection means, it is advantageous to use these devices in a flow-through mode, particularly by employing the flow injection (FI) approach. The capacity of FI, as offering itself as a complementary facility to augment the performance of biosensors, and in many cases as an attractive alternative, is demonstrated by reference to selected examples, comprising assays based on enzymatic procedures with optical and thermal detection procedures, and via description of a recently introduced technique for immunoassays, termed flow injection renewable surface immunoassays, which promises to entail powerful potentials and to yield compatible or better economy of operation than existing approaches.

Biosensing Techniques↗

PubMedDate not supplied

Biosensors in flow-injection systems for biomedical analysis, process and environmental monitoring.

This paper presents the construction of various biosensors using thin-film layers incorporated in flow injection devices, providing automated systems for biomedical analysis, process and environmental monitoring. A urease sensor has been developed in conjunction with a flow injection system for the automatic determination of urea. Use of the spraying immobilization technique gives rise to a response time of a few seconds, which allows sample throughputs up to 200 h-1. With a penicillin biosensor adapted in an appropriate cell detection, on-line measurements of penicillin V in the fermentation broth are achieved during the whole fermentation process; the results are compared with the HPLC method. Linearity, sensitivity and reproducibility of the biosensor are studied with regards to sample dilution in a stirred flow detection cell to provide optimal operating conditions. Measurements without any change in parameters are obtained during the whole fermentation process. Acetylcholinesterase sensors have been used in batch systems for the determination of pesticides, but they require large amounts of substrate. When those enzyme sensors are combined with flow injection systems, only small volumes (100 microliters) of substrate are injected into the carrier stream and an automated system can be obtained for continuous control of water quality.

Biosensing Techniques↗

PubMedDate not supplied

Ligand loading at the surface of an optical biosensor and its effect upon the kinetics of protein-protein interactions.

Optical biosensors are finding increasing use in the determination of kinetic and equilibrium constants for a variety of biomolecular interactions. Usually these biosensors require one biomolecule, the ligand, to be covalently attached to a hydrogel matrix which itself is bonded to the sensing surface. The ligands partner, the ligate, then binds from solution resulting in a measurable change in response which the instrument records as a function of time. Although in many cases, optical biosensors are used in order to obtain parameters that relate to interactions in solution, it is becoming clear that measurements involving the interaction of ligate with immobilized ligands on surfaces require careful experimental design. Here we report on how the density of ligand loading within the hydogel matrix affects the measured interaction kinetics. It is found that crowding of ligand within this matrix results in a significant reduction in the measured association rate constant, with a corresponding effect in the calculated overall affinity. However, measurements at low ligand loadings show association rate constants that are comparable to those measured in solution. Clearly, where this comparison is required, it is important to perform measurements under such conditions.

Biosensing Techniques↗

PubMed1998

High-density immobilization of an antibody fragment to a carboxymethylated dextran-linked biosensor surface.

There are numerous chemical methods published that enable protein coupling to carboxymethyl (CM) dextran. Here we have taken traditional amine coupling using N-hydroxysuccinimide (NHS) and N'-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and coupled an antibody fragment (scFv) to CM dextran at a very high density. Using an upgraded BIAlite from Biacore AB, more than 7000 RU of scFv was coupled to a CM dextran biosensor chip. In addition, scanning electron microscopy was performed on CM dextran biosensor chips following amine coupling of 30 nm gold anti-IgG particles. This showed that amine coupling was uniform across the biosensor chip surface. Calculations show that 7620 RU of an scFv coupled to such a surface results in a mean distance between binding sites of 8.8 nm. This equates to a packing volume of approximately 20% of the available space occupied by the antibody fragment. Comparisons made with densities of covalently coupled IgG show that a greater number of antibody fragment molecules can be coupled per unit area. This is most likely due to the smaller size of an antibody fragment (scFv), which has a volume of less than 20% of an IgG molecule. The significance of these findings is discussed.

Animals↗

PubMedDate not supplied

Biosensor analysis of the interleukin-2 receptor complex.

Surface plasmon resonance (SPR) biosensor technology has been a significant addition to the evolution and refinement of methods to study macromolecular interactions. Prior to the advent of SPR, we employed a variety of biochemical and biological techniques to study the interleukin-2/interleukin-2 receptor system (IL-2/IL-2R). By combining site-directed mutagenesis, equilibrium and kinetic radioligand binding, and competitive biological assays, we and others had begun to understand many aspects of the structure-activity relationships of the IL-2/IL-2R system. Due to the complexity of the IL-2R, cell-based assays proved limited in their ability to provide quantitative information on the binding characteristics of subclasses of the IL-2 receptor. SPR technology promised to be a new and powerful approach to the quantitative analysis of complex receptor systems. To demonstrate the feasibility of this technology, we employed Biacore analysis to investigate the ligand binding characteristics of novel, pre-assembled, IL-2R coiled-coil complexes. The results of these studies, although limited by instrumentation and data analysis, clearly established the utility of this method. Subsequently, by incorporating advancements in both of these areas, we have been able to carry out detailed kinetic analyses of the binding properties of individual IL-2R subunits as well as heteromeric complexes on the surface of a biosensor. Therefore, SPR biosensor analysis combined with other established analytical methods has proven to be a powerful tool for the analysis of complex hematopoietic receptor systems. Published in 1999 by John Wiley & Sons, Ltd.

Animals↗

PubMed2002

A biosensor for the detection of triazine and phenylurea herbicides designed using Photosystem II coupled to a screen-printed electrode.

A biosensor for the detection of triazine- and phenylurea-type herbicides was constructed using isolated Photosystem II (PS II) complexes as a biosensing element. PSII isolated from the thermophilic cyanobacterium Synechococcus elongatus was immobilized on the surface of a screen-printed sensor composed of a graphite working electrode and Ag/AgCl reference electrode deposited on a polymeric substrate. The biosensor was mounted in a flow microcell with illumination. The principle of the detection was based on the fact that herbicides selectively block PSII electron transport activity in a concentration-dependent manner. Changes of the activity were registered amperometrically as the rate of photoreduction of an artificial electron acceptor. The setup resulted in a reusable herbicide biosensor with a good stability (half-life of 24 h) and limit of detection of approximately 10(-9) M for diuron, atrazine and simazine.

Biosensing Techniques↗

PubMed2004

Whole cell-enzyme hybrid amperometric biosensor for direct determination of organophosphorous nerve agents with p-nitrophenyl substituent.

In this paper, we reported the construction of a hybrid biosensor for direct, highly selective, sensitive, and rapid quantitative determination of organophosphate pesticides with p-nitrophenyl substituent using purified organophosphorus hydrolase (OPH) for the initial hydrolysis and Arthrobacter sp. JS443 for subsequent p-nitrophenol oxidation. The biocatalytic layer was prepared by co-immobilizing Arthrobacter sp. JS443 and OPH on a carbon paste electrode. OPH catalyzed the hydrolysis of organophosphorus pesticides with p-nitrophenyl substituent such as paraoxon and methyl parathion to release p-nitrophenol that was oxidized by the enzymatic machinery of Arthrobacter sp. JS443 to carbon dioxide through electroactive intermediates 4-nitrocatechol and 1,2,4-benzenetriol. The oxidization current of the intermediates was measured and correlated to the concentration of organophosphates. The best sensitivity and response time were obtained using a sensor constructed with 0.06 mg dry weight of cell and 965 IU of OPH operating at 400 mV applied potential (vs. Ag/AgCl reference) in 50 mM citrate-phosphate pH 7.5 buffer at room temperature. Using these conditions, the biosensor measured as low as 2.8 ppb (10 nM) of paraoxon and 5.3 ppb (20 nM) of methyl parathion without interference from phenolic compounds, carbamate pesticides, triazine herbicides, and organophosphate pesticides that do not have the p-nitrophenyl substituent. The biosensor had excellent operational life-time stability with no decrease in response for more than 40 repeated uses over a 12-h period when stored at room temperature, while its storage life was approximately 2 days when stored in the operating buffer at 4 degrees C.

Actinobacteria↗

PubMed2005

Broad-spectrum protein biosensors for class-specific detection of antibiotics.

The dramatically increasing prevalence of multi-drug-resistant human pathogenic bacteria and related mortality requires two key actions: (i) decisive initiatives for the detection of novel antibiotics and (ii) a global ban for use of antibiotics as growth promotants in stock farming. Both key actions entail technology for precise, high-sensitive detection of antibiotic substances either to detect and validate novel anti-infective structures or to enforce the non-use of clinically relevant antibiotics. We have engineered prokaryotic antibiotic response regulators into a molecular biosensor configuration able to detect tetracycline, streptogramin, and macrolide antibiotics in spiked liquids including milk and serum at ng/mL concentrations and up to 2 orders of magnitude below current Swiss and EC threshold values. This broad-spectrum, class-specific, biosensor-based assay has been optimized for use in a storable ready-to-use and high-throughput-compatible ELISA-type format. At the center of the assay is an antibiotic sensor protein whose interaction with specific DNA fragments is responsive to a particular class of antibiotics. Binding of biosensor protein to the cognate DNA chemically linked to a solid surface is converted into an immuno-based colorimetric readout correlating with specific antibiotics concentrations.

Animals↗