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At least 1,405 records · Page 78Linked to original sources

PubMed1998

Proposal for standardizing direct-reading biosensors for blood glucose.

Direct-reading glucose biosensors sense molality (glucose per unit water mass) in the sample. With aqueous calibration, a direct-reading glucose biosensor produces higher results in blood and plasma than methods measuring concentration, theoretically by the ratio of water concentrations in calibrator and sample. To confirm this, we measured glucose in 14- blood and 40 plasma samples with the direct-reading glucose sensor in the Chiron Model 860 Blood Gas and Critical Analyte System and with our routine method (ESAT 6660; Eppendorf). The Chiron instrument is calibrated with a 10 mmol/L (180 mg/dL0 glucose calibrator (mass concentration of water = 0.99 kg/L). Assuming normal water concentrations of 0.84 and 0.93 kg/L in blood and plasma, respectively, we multiplied results from the Chiron sensor by 0.84/0.99 and 0.93/0.99 to obtain concentrations in blood and plasma. This conversion resulted in agreement of results with our routine method. An individual conversion based on hematocrit in each whole-blood sample was less satisfactory. To avoid confusion over variously measured and reported glucose results and reference values, we suggest standardization and reporting of whole-blood glucose results as equivalent plasma concentrations. This proposal may be conveniently achieved by using a commercially available reference material for glucose, NIST SRM 965.

Biosensing Techniques↗

PubMedDate not supplied

[Biosensors for detecting organic compounds. II. Sensors for carbohydrates, aromatic, heterocyclic and other organic compounds].

The use of biosensors for detecting aromatic compounds (aniline, hydroquinone, phenol, and N,N-dimethyl-p-phenylenediamine), heterocyclic compounds (adenosine, AMP, ATP, bilirubin, hypoxanthine, guanine, inosine, inosine 5'-phosphate, xanthine, creatinine, uric acid, and NAD), carbohydrates (glucose, galactose, lactose, maltose, and sucrose), vitamins, antibiotics, steroids, mutagens, and organophosphorous pesticides is discussed. Basic metrological characteristics of these biosensors are reviewed.

Biosensing Techniques↗

PubMed1998

Determination of Na channel blockers in paralytic shellfish toxins and pufferfish toxins with a tissue biosensor.

The biosensor consisted of a sodium electrode and covered with the frog bladder membrane within a flow cell was tested for the estimation of tetrodotoxin (TTX) and saxitoxin (STX). This sensor was applied to detect very low amounts of the Na+ channel blockers, STX and TTX, in different shellfishes and swellfishes. A good agreement was obtained between TTX activities determined by mouse assay and amounts of Na+ channel blockers estimated by frog membrane sensor. The lowest level of TTX (fg) that can be determined by frog membrane sensor does not cause human poisoning. The channel blockers in short-necked clam, which was assumed to be STX, were monitored by this sensor continuously every week for one year. It was discovered that the STX content increased from July until September and then decreased from October until March. The biosensor proposed here may be used for the estimation of STX and TTX conventionally in the future.

Animals↗

PubMedDate not supplied

[Physiologo-biochemical characteristics if Gluconobacter oxydans and prospects for its use in biotechnology and biosensor systems (review)].

Gluconobacter oxydans possesses a unique organization of metabolic systems, which are characterized by reduction of major dissimilation pathways, surface localization of main oxidative enzymes responsible for partial oxidation of carbon substrates, high performance of electron-transport chains, and accumulation of partially oxidized metabolites in the medium. These features allow us to use the cells of these microorganisms in biotechnology for production of several food products and medicines. The use of G. oxydans in biosensors for estimation of concentrations of sugars, aldoses and polyalcohols is promising. Physiological and biochemical features of these microorganisms enabling their use in biotechnology and receptor elements of biosensors are reviewed.

Acetobacteraceae↗

PubMedDate not supplied

[Detection of DNA autoantibodies using a novel amperometric biosensor on the basis of platinum(II) complex with DNA].

A biochemical biosensor was developed on the basis of a steady-state Hg-film electrode and either DNA molecules or antibodies to DNA immobilized in a cellulose nitrate film. This biosensor is designed to measure the concentration of DNA (or antibodies to DNA), and it can be used in the diagnosis of autoimmune diseases. Electric current of catalytic H2 evolution caused by complexing between DNA (antibodies to DNA) and Pt(II) was used as an analytical signal. The detection sensitivity threshold for DNA and antibodies to DNA was 10 and 0.075 microgram/ml, respectively.

Animals↗

PubMed1999

Detection of the deltaF508 (F508del) mutation of the cystic fibrosis gene by surface plasmon resonance and biosensor technology.

In the present paper, we applied surface plasmon resonance (SPR) and biosensor technologies for biospecific interaction analysis (BIA) to detect deltaF508 mutation (F508del) of the cystic fibrosis transmembrane regulator (CFTR) gene in both homozygous as well as heterozygous human subjects. The proposed method is divided into three major steps. The first step is the immobilization on a SA5 sensor chip of two biotinylated oligonucleotide probes (one normal, N-508, and the other mutant, deltaF508) that are able to hybridize to the CFTR gene region involved in F508del mutation. The second step consists of the molecular hybridization between the oligonucleotide probes immobilized on the sensor chips and (1) wild-type or mutant oligonucleotides, as well as (2) single-stranded DNA obtained by asymmetric polymerase chain reaction (PCR), performed using genomic DNA from normal individuals and from F508del heterozygous and F508del homozygous patients. The third, and most important, step consists of the evaluation of differential stabilities of DNA/DNA molecular complexes generated after hybridization of normal and deltaF508 probes immobilized on the sensor chips. The results obtained strongly suggest that the proposed procedure employing SPR technology enables a one-step, nonradioactive protocol for the molecular diagnosis of F508del mutation of the CFTR gene. This approach could be of interest in clinical genetics, as the hybridization step is oftenly required to detect microdeletions present within PCR products.

Biosensing Techniques↗

PubMed1998

Measurement of antigen-antibody interactions with biosensors.

The introduction in 1990 of a new biosensor technology based on surface plasmon resonance has revolutionized the measurement of antigen-antibody binding interactions. In this technique, one of the interacting partners is immobilized on a sensor chip and the binding of the other is followed by the increase in refractive index caused by the mass of bound species. The following immunochemical applications of this new technology will be described: (1) functional mapping of epitopes and paratopes by mutagenesis; (2) analysis of the thermodynamic parameters of the interaction; (3) measurement of the concentration of biologically active molecules; (4) selection of diagnostic probes.

Animals↗

PubMed1998

New approaches for the analysis of molecular recognition using the IAsys evanescent wave biosensor.

Trends in the analysis of molecular recognition using the IAsys evanescent wave biosensor are outlined. Diversification of sensor surface chemistry, an open cuvette format and the advent of robotics controlled by intelligent software are widening the range and throughput of applications. Analyses of binding and dissociation are now carried out across a wide spectrum of biomolecules, including protein, nucleic acid, carbohydrate and lipid. Determinations are obtained from a range of experimental formats. These include qualitative 'yes/no' screening assays, through semi quantitative ranking of kinetic association, dissociation and equilibrium constants for a family of binding partners, to deriving constants comparable with those which would be obtained in free solution. A dependence of the initial rate of biomolecular association on concentration allows analyte concentration to be measured--an increasingly common application class. This is often employed in situations where a rapid determination is required The ability to recover bound analyte from the sensor surface in sufficient amounts for subsequent characterization is opening up new routes to the parallel analysis of structure and function.

Animals↗

PubMed1998

Thermodynamic analysis of protein interactions with biosensor technology.

A methodology using biosensor technology for combined kinetic and thermodynamic analysis of biomolecular interactions is described. Rate and affinity constants are determined with BIAcore. Thermodynamics parameters, changes in free energy, enthalpy and entropy, are evaluated from equilibrium data and by using rate constants and transition state theory. The methodology using van't Hoff theory gives complementary information to microcalorimetry, since only the direct binding is measured with BIAcore whereas microcalorimetry measures all components, including e.g. hydration effects. Furthermore, BIAcore gives possibilities to gain new information by thermodynamic analysis of the rate constants.

Animals↗

PubMedDate not supplied

Active concentration measurements of recombinant biomolecules using biosensor technology.

Whereas the concentration of a biomolecule simply refers to the amount of chemical substance per unit of volume, its active concentration refers to a relational parameter that has meaning only with respect to the molecule's ability to interact specifically with one particular ligand. When proteins are studied in a biological context, it is the biologically active concentration that is relevant, and not the total concentration of correctly and incorrectly folded molecules. Using a biosensor instrument the concentration of active biomolecules in a preparation can be measured by injecting the preparation at different flow rates onto a sensor chip surface presenting a high concentration of a specific ligand. The method can be used under conditions of partial mass transport limitation and does not require a pre-established standard curve. When the method was used to measure the active concentration of several recombinant proteins it was found that the active concentration was much lower than the nominal concentration determined by conventional methods. The active concentration also depended on the ligand used in the binding assay, reflecting the fact that active concentration can only be defined with respect to one specific probe. Such discrepancies in concentration values, if undetected, may lead to erroneous conclusions regarding the properties and behaviour of recombinant proteins tested in different assays.

Antigens, CD↗

PubMed1999

Instrumental biosensors: new perspectives for the analysis of biomolecular interactions.

The use of instrumental biosensors in basic research to measure biomolecular interactions in real time is increasing exponentially. Applications include protein-protein, protein-peptide, DNA-protein, DNA-DNA, and lipid-protein interactions. Such techniques have been applied to, for example, antibody-antigen, receptor-ligand, signal transduction, and nuclear receptor studies. This review outlines the principles of two of the most commonly used instruments and highlights specific operating parameters that will assist in optimising experimental design, data generation, and analysis.

Animals↗

PubMed2000

Biosensor chip mass spectrometry: a chip-based proteomics approach.

Rapid advances in genomic sequencing, bioinformatics, and analytical instrumentation have created the field of proteomics, which at present is based largely on two-dimensional electrophoresis (2-DE) separation of complex protein mixtures and identification of individual proteins using mass spectrometry. These analyses provide a wealth of data, which upon further evaluation leads to many questions regarding the structure and function of the proteins. The challenge of answering these questions create a need for high-specificity approaches that may be used in the analysis of biomolecular recognition events and interacting partners, and thereby places great demands on general protein characterization instrumentation and the types of analyses they need to perform. Over the past five years we have been actively involved in interfacing two general, instrumental techniques, surface plasmon resonance-biomolecular interaction analysis (SPR-BIA) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, into a single concerted approach for use in the functional and structural characterization of proteins. Reviewed here is the recent progress made using biomolecular interaction analysis - mass spectrometry (BIA-MS) in the detailed characterization of proteins and protein-protein interactions and the development of biosensor chip mass spectrometry (BCMS) as a new chip-based proteomics approach.

Biosensing Techniques↗

PubMedDate not supplied

Practical considerations in BIA/MS: optimizing the biosensor-mass spectrometry interface.

Biomolecular interaction analysis mass spectrometry (BIA/MS) is a multiplexed analytical technique that utilizes a unique combination of surface plasmon resonance (SPR) and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the detection and analysis of small amounts of proteins residing in complex biological systems. In order to achieve high sensitivity during BIA/MS, certain experimental parameters and sequences of events need to be optimized and maintained. Immobilized ligand density, flow rate and biosensor control (in SPR-BIA) and matrix choice and application (in MALDI-TOF MS) have significant influence on the final outcome of the BIA/MS analysis and, consequently, need to be optimized and carefully controlled. In addition, chip washing and cutting are essential in converting the SPR-active sensor chips into target surfaces amenable to MALDI-TOF MS. Reviewed here are the prerequisites for successfully interfacing SPR-BIA with MALDI-TOF MS.

Biosensing Techniques↗

PubMedDate not supplied

From gel filtration to biosensor technology: the development of chromatography for the characterization of protein interactions.

The objective of this review is to summarize the development of chromatographic techniques for the determination of reaction stoichiometries and equilibrium constants for solute interactions of biological importance. Gel chromatography is shown to offer a convenient means of characterizing solute self-association as well as solute-ligand interactions. Affinity chromatography is an even more versatile method of characterizing interactions between dissimilar reactants because the biospecificity incorporated into the design of the affinity matrix ensures applicability of the method regardless of the relative sizes of the two reactants. Adoption of different experimental strategies such as column chromatography, simple partition equilibrium experiments and biosensor technology has created a situation wherein affinity chromatography affords a means of characterizing the whole range of reaction affinities-from relatively weak interactions (binding constants less that 10(3)M (-1)) to tight interactions with binding constants greater than 10(9)M (-1). In addition to its established prowess as a means of solute separation and purification, chromatography thus also possesses considerable potential for investigation of the functional roles of the purified reactants-an endeavour that requires characterization as well as identification of the interactions responsible for a physiological phenomenon.

Biosensing Techniques↗

PubMed2002

New transition-metal-dependent DNAzymes as efficient endonucleases and as selective metal biosensors.

Like proteins and RNA molecules, many DNA molecules have now been shown to catalyze a variety of reactions and are thus called DNAzymes. With limited building blocks, DNAzymes need to recruit other cofactors in order to match other enzymes in terms of reaction diversity and catalytic efficiency. Several unique properties make transition-metal ions an ideal choice of cofactor for DNAzymes. Indeed, new DNAzymes that bind transition-metal ions with high affinity and selectivity have been obtained through the use of a powerful combinatorial biology tool called in vitro selection. This accomplishment now makes it possible to obtain different classes of metallo-DNAzymes in the laboratory within a short period of time. It also offers a rare opportunity to compare and contrast structural and functional properties of metal-binding sites in proteins and in DNAzymes. The resulting transition-metal-dependent DNAzymes have displayed high activity toward cleavage of DNA and RNA and thus hold promise for their biochemical and pharmaceutical applications. Finally, the use of DNAzymes as a new class of highly sensitive and selective biosensors for metal ions has been demonstrated recently.

Journal Article↗

PubMed1999

The gramicidin-based biosensor: a functioning nano-machine.

Biosensors combine a biological recognition mechanism with a physical transduction technique. In nature, the transduction mechanism for high sensitivity molecular detection is the modulation of the cell membrane ionic conductivity through specific ligand-receptor binding-induced switching of ion channels. This effects an inherent signal amplification of six to eight orders of magnitude, corresponding to the total ion flow arising from the single channel gating event. Here we describe the first reduction of this principle to a practical sensing device, which is a planar impedance element composed of a macroscopically supported synthetic bilayer membrane incorporating gramicidin ion channels. The membrane and an ionic reservoir are covalently attached to an evaporated gold surface. The channels have specific receptor groups attached (usually antibodies) that permit switching of gramicidin channels by analyte binding to the receptors. The device may then be made specific for the detection of a wide range of analytes, including proteins, drugs, hormones, antibodies, DNA, etc., currently in the 10(-7)-10(-13) M range. It also lends itself readily to microelectronic fabrication and signal transduction. By adjusting the surface density of the receptors/channel components during fabrication, the optimum sensitivity range of the device may be tuned over several orders of magnitude.

Anti-Bacterial Agents↗

PubMedDate not supplied

A nitric oxide biosensor based on horseradish peroxidase/kieselguhr co-modified pyrolytic graphite electrode.

A reagentless nitric oxide (NO) biosensor was prepared using a pyrolytic graphite (PG) electrode modified with a composite film containing horseradish peroxidase (HRP) and kieselguhr. Noticeably, the electron-transfer reactivity of HRP was significantly enhanced when incorporated in the inorganic kieselguhr material. Consequently, we observed the direct electrochemical response of HRP in this composite film, which would be otherwise electrochemically silent (in the absence of kieselguhr). Importantly, this modified electrode demonstrated nice catalytic activity, as well as high stability, towards the reduction of NO. The peak current related to NO was linearly proportional to its concentration from 2.0 x 10(-7) to 2.0 x 10(-5) mol/L, and the relative standard deviation was 4 % for five successive determinations at a NO concentration of 1.0 x 10(-5) mol/L. The critical level in concentration was estimated to be (4.0 +/- 0.3) x 10(-8) mol/L.

Biological Assay↗

PubMed1989

Luminescence biosensors.

A novel optical biosensor for homogeneous immunoassay has been developed on the basis of the finding that electrochemical luminescence of pyrene-labelled antigen is extremely inhibited by immunochemical complexation. Electrochemical luminescence homogeneous immunoassay for human serum albumin (HSA), as a model analyte, was performed with a platinum plate electrode which was located in the vicinity of an optical fibre tip. HSA was determined in the concentration range of 3-25 X 10(-6) mol/l. To improve electrochemical luminescence measurement an optical fibre electrode has been developed by fabricating a transparent platinum film on the top of an optical fibre. The minimum detectable limit of luminol was 10(-11) mol/l with the optical fibre electrode. Luminol was applied as a label for homogeneous immunoassay.

Biosensing Techniques↗