SEARCH · PubMed Health

Results for “biosensor”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources

PubMed1992

Monitoring glutamine in mammalian cell cultures using an amperometric biosensor.

An amperometric biosensor has been developed for monitoring glutamine in the pulsed-batch cultivation of murine hybridoma cells. Glutamine oxidase was cross-linked with bovine serum albumin (BSA) via glutaraldehyde activation and deposited on a preactivated nylon membrane. Glutaminase was then immobilized on the protein layer and the resulting membrane was attached to the sensing area of a hydrogen peroxide probe (platinum vs silver/silver chloride polarized at +0.7 V). An orthogonal test was performed to optimize the activity of the membrane for glutamine with respect to the concentrations of glutamate oxidase, BSA, glutaminase and glutaraldehyde. There was an excellent linear relationship between the biosensor's response and glutamine in the range 0.1-3 mM. The determination of glutamine could be performed in 2 min and each membrane was reused for at least 300 consecutive analyses. The data obtained also agreed well with those high-performance liquid chromatography, thus validating the applicability of the biosensor.

Amino Acid Oxidoreductases↗

PubMed1993

Improvement of the selectivity of an FIA amperometric biosensor system for glucose.

A flow injection analysis (FIA) biosensor system has been developed for the determination of glucose from urine, blood plasma and foodstuffs. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an enzyme column. The hydrogen peroxide released from the conversion of glucose to gluconic acid was monitored by a platinum electrode vs. silver/silver chloride poised at +700 mV. As a novel aspect to the improvement of the selectivity of the biosensor system, an anion exchange column was placed upstream to remove uric acid, ascorbic acid or acetaminophen, three major electroactive interfering substances which usually occur in urine and blood plasma. Among several resins tested, the effective adsorption of uric and ascorbic acids could be accomplished using an acetate anion exchanger, and the selectivity coefficient was pH dependent. The binding of acetaminophen to the resin was much less efficient and, in all cases, the selectivity coefficient was independent of the operating temperature up to 37 degrees C. When applied to real samples, the data obtained by the biosensor system compared well with those of the standard hexokinase assay. The immobilized glucose oxidase could be reused for at least 2000 repeated analyses without loss of its original activity.

Acetaminophen↗

PubMed1993

Dynamic concentration challenges for biosensor characterization.

A method and apparatus are described for characterization of the steady state and dynamic response of biosensors. The apparatus produces a steady stream of homogeneously mixed analyte whose concentration can be fixed at discrete values or varied continuously. The device is ideally suited for continuously operated biosensors, but is also effective for biosensors that operate in discrete sampling modes. The system permits simultaneous testing of several sensors and determination of the accuracy, precision and repeatability of sensor response. The characteristics of this testing apparatus were validated with ferrocyanide and glucose as indicators. As an example of use of the apparatus, concentration ramps were created and used to complement conventional step changes for characterizing an implantable glucose sensor. The ramp rate can be adjusted easily by scaling the apparatus to simulate the rate of concentration change anticipated during actual monitoring situations.

Animals↗

PubMed1994

Thin-film conductometric biosensors for glucose and urea determination.

The characteristics of the developed conductometric biosensors for urea and glucose determination are described. Conductometric transducers based on thin-film interdigitated metal (Au, Cr, Cu, Ni) electrodes were studied, and enzymes urease and glucose oxidase were used for the selective membranes formation on the chips having gold electrodes. The influence of ionic strength and buffer capacity of the samples on the biosensors response in kinetic and steady-state modes of measurements was thoroughly tested. It was shown that the kinetic response of the sensors does not depend on the buffer capacity of the analyzed sample. In basic features the performance of the developed biosensors is rather close to that of respective enzyme field effect transistor, though the former are much superior when the technological complexity of the transducer itself is considered and taking into account that conductometric sensors require no reference electrode.

Biosensing Techniques↗

PubMed1995

Enzyme biosensor for urea based on a novel pH bulk optode membrane.

A new, absorbance-based enzymatic biosensor membrane for determination of urea is described. A lipophilic, fully LED- and diode laser-compatible pH sensitive dye was incorporated into a plasticized, carboxylated poly(vinyl chloride) membrane and served as the optical transducer of the sensor. Urease was covalently linked to the surface of the pH bulk optode membrane to form a very thin cover. The resulting biosensor membrane allows rapid determination of urea over the 0.3 to 100 mM range. The reproducibility, stability, and effects of pH and buffer concentration on the response of sensor are reported. The preparation of the pH transducer and the immobilization of the enzyme are simple and may easily be adopted to other biosensor types.

Animals↗

PubMed1996

Enzyme support systems for biosensor applications based on gold-coated nylon meshes.

A novel experimental protocol for enzyme immobilization based on the use of a very permeable support is described and applied to the development of an acetylcholinesterase (AChE) based biosensor. In this system, the enzyme was immobilized onto a gold-coated nylon mesh via a self-assembled monolayer of a bifunctional reagent, cystamine, preadsorbed onto the gold surface. This support has been characterized by optical microscopy and electrochemical measurements of permeability. In the assembled biosensor, the AChE modified mesh was placed over a glassy carbon electrode and the response to 4-aminophenylacetate, used as substrate, was monitored via the enzymatic reaction product, 4-aminophenol, by oxidation at +0.25 V vs. SSCE. This approach to biosensor design has been extended to the determination of organophosphorus and carbamate pesticides by their inhibition of AChE enzymatic activity.

Acetylcholinesterase↗

PubMed1996

Lactate solid-state biosensor with multilayer of electrodeposited polymers for flow-injection clinical analysis.

In the lactate biosensor, electrodeposited poly(o-phenylenediamine) serves as a convenient matrix for the immobilization of lactate oxidase, but does not provide sufficient discrimination from several interfering species present in physiological fluids. Their effect, however, can be eliminated by additional modification of the working Pt electrode with a bilayer of electrodeposited polypyrrole/polyphenol. Despite continued decrease in biosensor sensitivity, the newly developed three-layer solid-state biosensor was successfully applied in flow-injection determination of lactate in both undiluted and diluted human blood serum samples over a 10 day period. For the lactate concentration range 0.2-5.0 mM in several series of measurements the correlation coefficient values for comparison with photometric determination using a DuPont dimension clinical analyzer were between 0.96 and 0.99. The reproducibility measured for 1:10 diluted serum was 0.6%. The detection limit was estimated as 2 microM.

Acetaminophen↗

PubMed1996

A fractal analysis of the influence of non-specific binding on antigen-antibody binding kinetics for biosensor applications.

A fractal analysis of the influence of non-specific binding on the specific binding of antigen in solution to antibody immobilized on a biosensor surface is presented for first-, one and a half-, second, and other-order reactions occurring under external diffusion-limited conditions. Both single-step and dual-step binding of antigen in solution to antibody immobilized on the surface is considered. For a first-order reaction, an increase in the fractal parameters, b, leads to a decrease in the amount of antigen in solution bound specifically to the antibody on the surface when non-specific binding is either absent or present. The presence of non-specific binding leads to a decrease in the amount of antigen bound to the antibody on the surface. For a one and a half- and for second-order reactions and when non-specific binding is either absent or present to a small degree (alpha = 0.01), an increase in the fractal parameter, b, leads to a decrease in the amount of antigen bound specifically to the antibody immobilized on the biosensor surface. However, for an alpha value of 0.1, the maximum rate and the amount of antigen bound specifically to the antibody immobilized on the biosensor surface is obtained for fractal parameter values of 0.2 and 0.4, and 0.4 for the one and a half- and for second-order reactions, respectively. Apparently, some amount of heterogeneity is helpful in obtaining the optimum amount and rate of antigen in solution bound specifically to the antibody on the surface for reaction orders higher than one. The applicability of the approach to real antibody surfaces is demonstrated.

Antigen-Antibody Reactions↗

PubMed1996

Application of biosensor for monitoring galactose content.

The quality and quantity of different sugars play a very important role in studying the carbohydrate metabolism of yeast. During the bioprocesses there is a need to follow the concentrations of these sugars. Authors have reported on the development of biosensors for determination of glucose and maltose previously. The aim of this research was to construct a sensor for determining galactose in fermentation broths to prepare the basis for an online monitoring system. Using a modified thin-layer enzyme cell connected to an electrochemical detector cell, a biosensor has been developed for this purpose. Galactose was oxidized with immobilized galactose oxidase enzyme (EC 1.1.3.9) and the hydrogen peroxide generated during the enzyme reaction was determined with an amperometric detector. The parameters for the biochemical and electrochemical reactions were optimized. The pH optimum of 6.6 was found when using phosphate buffer. The buffer solution completed by micro elements (Mg2+, Se2+) gave more stable signs. The activities for raffinose, lactose, glycerol and dihydroxyacetone were 68, 16, 6 and 430%, respectively. With the thin-layer cell more than 900 samples were measured in 6 weeks. Samples obtained from different fermentations were measured with the newly developed galactose sensor and the results were compared with the standard UV method. The correlation coefficient was 0.991. The results showed that the application of the new biosensor was successful.

Biosensing Techniques↗

PubMed1996

Electrochemical biosensors for medicine and ecology.

Research results obtained in the last 3 years in the area of electrochemical amperometric biosensors are presented. Selective electrochemical biosensors are proposed on the basis of investigations of electrode materials, electrolyte content, selective properties of polymer materials and mediators influence. Biosensor parameters for determination of glucose, phenol and biological oxygen demand are described.

Biosensing Techniques↗

PubMed1995

Metrological opportunities of the dynamic mode of operating an enzyme amperometric biosensor.

An algorithm for generating calibration curves that reflects the peculiarities of the dynamic mode of operating of the amperometric biosensor, created on the base of numerical simulations of the sensor behaviour, is proposed. The most important steps are: selection of the informative quantity about the sensor current versus time relationship and the calibration curve processing. Five different informative quantities are tested as well as two ways of representation of calibration curves. The object of study is enzyme catalyzed selective reaction. The values of the kinetic constants used reflect the conversion of glucose to gluconolacton catalyzed by glucose oxidase (GOD) and catalase (CAT). The results show that sensors with different metrological characteristics can be created by means of a selection of informative quantity of the signal of one biosensor transducer. In addition there appears to be a possibility of facilitating the calibration procedure and prolonging the life of the biosensor.

Algorithms↗

PubMed2004

A Biacore biosensor method for detailed kinetic binding analysis of small molecule inhibitors of p38alpha mitogen-activated protein kinase.

Protein kinases are emerging as one of the most intensely studied classes of enzymes as their central roles in physiologically and clinically important cellular signaling events become more clearly understood. We report here the development of a real-time, label-free method to study protein kinase inhibitor binding kinetics using surface plasmon resonance-based biomolecular interaction analysis (Biacore). Utilizing p38alpha mitogen-activated protein kinase as a model system, we studied the binding properties of two known small molecule p38alpha inhibitors (SB-203580 and SKF-86002). Direct coupling of p38alpha to the biosensor surface in the presence of a reversible structure-stabilizing ligand (SB-203580) consistently produced greater than 90% active protein on the biosensor surface. The dissociation and kinetic constants derived using this Biacore method are in excellent agreement with values determined by other methods. Additionally, we extend the method to study the thermodynamics of small molecule binding to p38alpha and derive a detailed thermodynamic reaction pathway for SB-203580. The Biacore method reported here provides an efficient way to directly and reproducibly examine dissociation constants, kinetics, and thermodynamics for small molecules binding to p38alpha and possibly other protein kinases. Immobilization in the presence of a stabilizing ligand may further represent a broadly applicable paradigm for creation of highly active biosensor surfaces.

Animals↗

PubMed2004

A glucose biosensor based on chitosan-glucose oxidase-gold nanoparticles biocomposite formed by one-step electrodeposition.

An amperometric biosensor for the quantitative measurement of glucose is reported. The biosensor is based on a biocomposite that is homogeneous and easily prepared. This biocomposite is made of chitosan hydrogel, glucose oxidase, and gold nanoparticles by a direct and facile electrochemical deposition method under enzyme-friendly conditions. The resulting biocomposite provided a shelter for the enzyme to retain its bioactivity at considerably extreme conditions, and the decorated gold nanoparticles in the biocomposite offer excellent affinity to enzyme. The biosensor exhibited a rapid response (within 7s) and a linear calibration range from 5.0 microM to 2.4 mM with a detection limit of 2.7 microM for the detection of glucose. The combination of gold nanoparticles affinity and the promising feature of the biocomposite with the onestep nonmanual technique favor the sensitive determination of glucose with improved analytical capabilities.

Biocompatible Materials↗

PubMed2004

Simultaneous determination of renal clinical analytes in serum using hydrolase- and oxidase-encapsulated optical array biosensors.

An optical array biosensor encapsulated with hydrolase and oxidoreductase using sol-gel immobilization technique has been fabricated for simultaneous analysis and screening of multiple samples to determine the presence of multianalytes which are clinically important in relation to renal failure. Urease and creatinine deiminase were used to detect urea and creatinine, while glucose oxidase and uricase were coimmobilized with horseradish peroxidase to quantify glucose and uric acid. Moreover, the concentrations of analytes in fetal calf serum were measured and quantified using the developed sensing system. The array biosensor showed good specificity for the simultaneous analysis of multiple samples for multianalytes without obvious cross-interference. The analytical ranges of the four analytes were between 0.01 and 10mM with detection limits of 2.5-80 microM. High precision with relative standard deviations of 3.8-9.2% (n=45) was also demonstrated. The reproducibility of array-to-array in 3 consecutive months was 5.4% (n=3). Moreover, the concentrations of analytes in fetal calf serum were 5.9 mM for urea, 0.13 mM for creatinine, 3.3mM for glucose, and 0.15 mM for uric acid, which were in good agreement with results obtained using the traditional spectroscopic methods. These results demonstrate the first use of a sol-gel-derived optical array biosensor for simultaneous analysis of multiple samples for the presence of multiple clinically important renal analytes.

Aminohydrolases↗

PubMed2004

A ready-to-use fluorimetric biosensor for superoxide radical using superoxide dismutase and peroxidase immobilized in sol-gel glasses.

In this work, a highly sensitive fluorescent biosensor for quantitative superoxide radical detection, based on the coupled reaction superoxide dismutase-peroxidase enzymes and the use of the probe Amplex red, is described. Superoxide anion radical was produced via oxidation of xanthine by xanthine oxidase. Dismutation of superoxide was catalyzed by superoxide dismutase, generating hydrogen peroxide, which reacted stoichiometrically with the nonfluorescent Amplex red, in the presence of peroxidase, yielding the red-fluorescent oxidation product resorufin. The coupled superoxide dismutase-peroxidase system was immobilized in a single sol-gel matrix. The enzymatic activity of the encapsulated superoxide dismutase-peroxidase system was nearly identical to that of one of the soluble enzymes, indicating that sol-gel encapsulation preserved the hierarchy of the enzyme's activity. Specificity and reusability of the encapsulated system for up to four cycles were also demonstrated. The fluorescent biosensor was able to detect concentrations of superoxide as low as 20 nM in phospholipid model membranes composed of saturated or unsaturated phospholipids. These facts make this biosensor a simple, reliable, and highly sensitive method with a potential use in biological systems, food, and drinks.

Anions↗

PubMed2004

Monitoring aromatic hydrocarbons by whole cell electrochemical biosensors.

In this article, we describe a bacterial whole cell electrochemical biosensors system that can be used for monitoring aromatic hydrocarbons. These bacterial biosensors are based on fusions of a promoter that is sensitive to aromatic compounds (the promoter region of the xylS gene and the xylR gene coding for the transcriptional regulator of the xyl operon) to reporter genes that can be monitored electrochemically at real-time and on-line. The xylS promoter was fused upstream of two promoterless genes coding the lacZ gene and phoA. These constructs reacted specifically to aromatic compounds but not to nonaromatic compounds, and we could detect, within minutes, micromolar concentrations of different aromatic hydrocarbons such as xylene and toluene. The use of two different reporter genes allows the future construction of a multianalyte detection system for simultaneous monitoring of several pollutants. These whole cell biosensors are potentially useful for on-line and in situ detection of aromatic compounds and as early warning systems of environmental hazards.

Alkaline Phosphatase↗

PubMed2005

Homogeneous enzyme immunoassay modified for application to luminescence-based biosensors.

Application of immunoassay to biosensors for use in the point-of-care setting ideally requires immunoassay without separation steps and with small volumes of both sample and reagents. The suitability of cloned enzyme donor immunoassay (CEDIA), one of a few homogeneous immunoassays available, was investigated for application to biosensors. This method is based on the bacterial enzyme beta-galactosidase, which has been genetically engineered by others into two inactive fragments, enzyme donor (ED) and enzyme acceptor (EA). Association of the ED and EA fragments in the assay results in formation of active enzyme, which acts on substrate to generate a detectable signal. Sensitivity of commercially available CEDIA kits were compared, with respect to the sample and reagent volumes, using three different signal generation processes. The CEDIA kit for valproic acid and three substrates, a colorimetric (chlorophenol red-beta-D-galactopyranoside), a chemiluminescent (Lumi-Gal 530), and a bioluminescent (Beta-Glo Assay System), were employed in the study. Our results indicate that the high sensitivity of the bioluminogenic substrate, D-luciferin-O-beta-galactopyranoside, with short assay time and small volumes of sample and reagents required for the assay, simple handling, and relatively low expense, make this substrate, together with CEDIA, suitable for application to biosensors intended for drug and metabolite monitoring in the point-of-care setting.

Biosensing Techniques↗

PubMed2005

Solubilization, stabilization, and purification of chemokine receptors using biosensor technology.

Establishing solubilization conditions for membrane-associated receptors is often a tedious empirical process. Here we describe a novel application of SPR biosensor technology to screen solubilization conditions automatically and to assess receptor activity directly. We focus on two chemokine receptors, CXCR4 and CCR5, which are important in HIV cell invasion. The autosampler in Biacore 3000 permitted whole cells expressing C-terminally tagged receptors to be automatically lysed under a given solubilization condition and the lysates to be injected over an antibody surface. The total amount of solubilized receptor could be quantitated from the antibody capture level, whereas the amount of active receptor could be quantitated using a subsequent injection of conformationally sensitive antibody or protein. Using this approach, we identified detergent/lipid/buffer combinations that enhanced and maintained receptor activity. We also used the biosensor to demonstrate CD4-dependent binding of gp120 to solubilized CCR5 and to develop affinity chromatography-based purification methods that increased receptor activity more than 300%. Together, these results illustrate the benefits of using the biosensor as a tool for isolating functional membrane receptors and for analyzing ligand/receptor interactions.

Automation↗