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 505 records · Page 28Linked to original sources

PubMed1993

Polymer materials in biosensors.

Fundamentals and application examples of polymeric materials in different types of biosensors and presented and discussed in view of their molecular structure and biosensor design and construction. The role of a series of polymers with respect to their typical application and their specific properties, like sensitivity and stability, is highlighted. Future trends of polymer materials for biosensors in the area of medical and environmental applications are outlined.

Biosensing Techniques↗

PubMed1994

Biosensors: a viable monitoring technology?

Biosensors for practical in vivo and in vitro applications are dependent on the effective integration of several biological and physical technologies. This review paper was stimulated by an IEE seminar. Some of the more recent advances aimed at taking techniques of fundamental and academic interest to various forms of practical reagentless biochemical analysis are highlighted, with associated clinical and commercial consequences. The paper describes some of the most recent developments in biosensor research, in particular those relating to material aspects of fabrication, including multilayer films for sensor applications, advances in ISFETs, conjugated polymers, new developments in quartz crystal based biosensors, as well as advances in amperometric enzyme electrodes and the application of devices for continuous monitoring.

Biosensing Techniques↗

PubMedDate not supplied

Antigen-antibody binding kinetics for biosensor applications. A dual-fractal analysis.

The diffusion-limited binding kinetics of antigen (or antibody) in solution to antibody (or antigen) immobilized on a biosensor surface is analyzed within a fractal framework. The fit obtained by a dual-fractal analysis is compared with that obtained from a single-fractal analysis. In some cases, the dual-fractal analysis provides an improved fit when compared with a single-fractal analysis. This was indicated by the regression analysis provided by Sigmaplot (San Rafael, CA). These examples are presented. It is of interest to note that the state of disorder (or the fractal dimension) and the binding rate coefficient both increase (or decrease, a single example is presented for this case) as the reaction progresses on the biosensor surface. For example, for the binding of monoclonal antibody MAb 49 in solution to surface-immobilized antigen, a 90.4% increase in the fractal dimension (Df1 to Df2) from 1.327 to 2.527 leads to an increase in the binding rate coefficient (k1 to k2) by a factor of 9.4 from 11.74 to 110.3. The different examples analyzed and presented together provide a means by which the antigen-antibody reactions may be better controlled by noting the magnitude of the changes in the fractal dimension and in the binding rate coefficient as the reaction progresses on the biosensor surface.

Antigen-Antibody Reactions↗

PubMed1992

Determination of urinary glucose by a flow injection analysis amperometric biosensor and ion-exchange chromatography.

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA) amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous urate in urine samples was effectively retained by an upstream anion-exchange resin column. The biosensor system possessed a sensitivity of 160 +/- 2.4 RU microM-1 (RU or relative unit is defined as 2.86 microV at the detection output) for glucose with a minimum detection level of 10 microM. When applied for the determination of urinary glucose, the result obtained compared very well with that of the widely accepted hexokinase assay. The immobilized glucose oxidase could be reused for more than 1000 repeated analyses without losing its original activity. The reuse of the acetate anion-exchange column before replacement would be about 25-30 analyses. Acetaminophen and ascorbic acid were also effectively adsorbed by the acetate anion exchanger. The introduction of this type of anion exchanger thus greatly improved the selectivity of the FIA biosensor system and fostered its applicability for the determination of glucose in urine samples.

Adult↗

PubMed1994

Biosensor analysis of antigen-antibody interactions as a priority step in the generation of monoclonal bispecific antibodies.

A biosensor system aimed at real-time measuring molecular interactions among label-free reactants has been used for a comparative analysis of the binding features (i.e., association-dissociation rates and affinity constants) as well as epitope mapping between bivalent monoclonal antibodies and the derived monovalent bispecific monoclonal antibody. The results show that observed different affinities between parental and derived bispecific antibodies concern the association rate constant, whereas the dissociation rate constants are unaltered. The apparent affinity-constant values determined by solid-phase radioimmunoassay yielded figures almost overlapping with those obtained with the biosensor instrument. The results of the present work indicate that the biosensor system has gained a key role not only as a tool for the study of antigen-antibody interactions, but also for setting up the reference parameters for the selection of the best candidates in the generation of bispecific monoclonal antibodies.

Antibodies, Monoclonal↗

PubMed1995

Evanescent wave biosensors. Real-time analysis of biomolecular interactions.

Optical biosensors, based on evanescent wave technology, are analytical devices that measure the interactions between biomolecules in real time, without the need for any labels. Specific ligands are immobilized to a sensor surface, and a solution of receptor or antibody is injected over the top. Binding is measured by recording changes in the refractive index, caused by the molecules interacting near the sensor surface within the evanescent field. Evanescent wave-based biosensors are being used to study an increasing number of applications in the life sciences, including the binding and dissociation kinetics of antibodies and receptor-ligand pairs, protein-DNA and DNA-DNA interactions, epitope mapping, phage display libraries, and whole cell- and virus-protein interactions. There are currently four commercially available evanescent wave biosensors on the market. This article describes the technology behind their sensing techniques, as well as the range of applications in which they are employed.

Animals↗

PubMed1993

An improved FIA biosensor for the determination of aspartame in dietary food products.

A flow injection analysis (FIA) biosensor system was developed for the determination of the artificial sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester). The system consisted of an enzyme column of pronase immobilized on activated arylamine glass beads and a L-amino acid oxidase electrode connected in series. The dipeptide bond of aspartame was cleaved by immobilized pronase to release phenylalanine, which was in turn monitored by the enzyme electrode that used L-amino acid oxidase immobilized on a preactivated nylon membrane in combination with an amperometric electrode (platinum vs silver/silver chloride, 700 mV). The response of the FIA biosensor was linear up to 1 mM aspartame with a lower detection limit of 25 microM and had good reproducibility (rsd 0.3%). The FIA biosensor was stable for at least 30 h of continuous use at Tr. Each assay takes 4 min giving a sample throughput of 15 h-1. When applied to aspartame in dietary food products the results obtained agreed well with those reported by the product manufacturers.

Aspartame↗

PubMed2002

Biosensors designed for environmental and food quality control based on screen-printed graphite electrodes with different configurations.

Graphite electrodes fabricated by screen-printing have been used as amperometric detectors in biosensors based on NAD(+)-dependent dehydrogenases, tyrosinase, or genetically modified acetylcholinesterases. The mono-enzyme sensors have been optimized as disposable or reusable devices for detection of a variety of substrates important in the food industry ( D-lactic acid, L-lactic acid, acetaldehyde) or in environmental pollution control (phenols and dithiocarbamate, carbamate and organophosphorus pesticides). The sensors were prepared in four configurations differing in enzyme confinement, enzyme immobilization and location of the immobilization agent in the biosensor assembly. Tests on real samples have been performed with the biosensors; D-lactic acid and acetaldehyde have been detected in wine and phenols in air.

Acetaldehyde↗

PubMed2002

Properties of glucose biosensors based on dendrimer layers. Effect of enzyme immobilization.

The properties of glucose biosensors based on dendrimer layers on a gold support, which depend on the method of immobilization of glucose oxidase (GOX), were studied by amperometry. The kinetic parameters of enzymatic reactions, response time, sensitivity, detection limit, linear range, and enzyme turnover were determined. We showed that a more stable and sensitive sensor was obtained when GOX was immobilized on the dendrimer by crosslinking with glutaraldehyde in vacuum. This biosensor was stable for at least eight weeks. The response time was approximately 1.3 min, the detection limit of glucose was 25 micro M, and the apparent Michaelis-Menten constant was relative low ( K(m)=1.1+/-0.1 mM) in comparison with that for GOX in solution. The reason for these differences is discussed. The example of the application of the developed biosensors for the detection of mercury is also presented. The inhibitory effect of mercury on GOX activity was observed at mercury concentration of 100 nM.

Biosensing Techniques↗

PubMed2003

Simple optical fibre biosensor based on immobilised enzyme for monitoring of trace heavy metal ions.

A simple optical fibre biosensor based on immobilised enzyme for monitoring of trace heavy metal ions has been developed. The biosensor recognition system was designed based on the inhibition of urease activity, where the urease is immobilised on ultrabind membrane. The studies of inhibition by the heavy metal ions Hg(II), Ag(I), Cu(II), Ni(II), Zn(II), Co(II) and Pb(II) were performed using a fibre-optic biosensor configuration, where the pH change resulting from the bio-catalytic hydrolysis of urea was monitored at the wavelength 615 nm spectroscopically, using commercial pH indicator strip before and after the exposure to the heavy metal ions. The immobilised urease was regenerated by l-cysteine. The linear response range between 1 x 10(-9)-1 x 10(-5) M and the limit of detection 1 x 10(-9 )M (0.2 microg/L) for Hg(II) ions was achieved by employing the flow method. The optimisation of experimental parameters, including flow method, is also discussed.

Biosensing Techniques↗

PubMed2005

Lichen-based biosensor for the determination of benzene and 2-chlorophenol: microcalorimetric and amperometric investigations.

Preliminary microcalorimetric studies have been performed to analyse the response of a whole epiphytic lichen tissue (Evernia prunastri) to 2-chlorophenol (2Cl-phi), a pollutant of oil mill waste-water, in order to evaluate whether the tissue might be used to assess the toxic characteristics of polluted waters. The obtained results (lichen viability expressed in hours, enthalpy variations for the 2Cl-phi/lichen interactions) were used to create a lichen-based biosensor that uses an amperometric oxygen electrode (a Clark electrode) as a transducer. The lichen catalyses aromatic ring cleavage (via pyrocatechase enzymes present in the lichen), and transforms aromatic substances like 2Cl-phi into muconic acid (C6H6O4). Following a full electroanalytical characterisation, the performance of the proposed lichen biosensor was compared to that of a biosensor based on Pseudomonas putida cells, which was originally constructed to monitor benzene in different matrices (water, air, petrol and oil) and was tested in our laboratory previously.

Benzene↗

PubMed2005

Reagentless biosensor for phenolic compounds based on tyrosinase entrapped within gelatine film.

A simple and new reagentless phenolic compound biosensor was constructed with tyrosinase immobilized in the gelatine matrix cross-linked with formaldehyde. The morphologies of gelatine and gelatine/tryosinase were characterized by SEM. The tyrosinase retains its bioactivity when being immobilized by the gelatine film. Phenolic compounds were determined by the direct reduction of biocatalytically liberated quinone at -0.1 V vs SCE. The process parameters for the fabrication of the enzyme electrode were studied. Optimization of the experimental parameters has been performed with regard to pH, operating potential, temperature and storage stability. This biosensor exhibits a fast amperometric response to phenolic compounds. The linear range for catechol, phenol, and p-Cresol determination was from 5 x 10(-8) to 1.4 x 10(-4) M, 5 x 10(-8) to 7.1 x 10(-5)M, and 1 x 10(-7) to 3.6 x 10(-5)M, with a detection limit of 2.1 x 10(-8) M, 1.5 x 10(-8) M, and 7.1 x 10(-8 )M, respectively. The enzyme electrode retained ca.77% of its activity after 7 days of storage at 4 degrees C in a dry state. The proposed sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D.=8.6%) for eight different biosensors and was applied for determination in water sample. The recovery for the sample was from 99.0% to 99.8%.

Benzoquinones↗

PubMed2005

Construction of glucose biosensor based on sorption of glucose oxidase onto multilayers of polyelectrolyte/nanoparticles.

A new approach to constructing an enzyme-containing film on the surface of a gold electrode for use as a biosensor is described. A basic multilayer film (BMF) of (PDDA/GNPs)n/PDDA was first constructed on the gold electrode by electrostatic layer-by-layer self-assembly of poly(diallyldimethylammonium chloride) (PDDA) and gold nanoparticles (GNPs). Glucose oxidase (GOx) was then sorbed into this BMF by dipping the BMF-modified electrode into a GOx solution. The assembly of the BMF was monitored and tested via UV-vis spectroscopy and cyclic voltammetry (CV). The ferrocenemethanol-mediated cyclic voltammograms obtained from the gold electrode modified with the (PDDA/GNPs)n/PDDA/GOx indicated that the assembled GOx remained electrocatalytically active for the oxidation of glucose. Analysis of the voltammetric signals showed that the surface coverage of active enzyme was a linear function of the number of PDDA/GNPs bilayers. This result confirmed the penetration of GOx into the BMF and suggests that the BMF-based enzyme film forms in a uniform manner. Electrochemical impedance measurements revealed that the biosensor had a lower electron transfer resistance (Ret) than that of a sensor prepared by layer-by-layer assembly of PDDA and GOx, due to the presence of gold nanoparticles. The sensitivity of the biosensor for the determination of glucose, which could be controlled by adjusting the number of PDDA/GNPs bilayers, was investigated.

Adsorption↗

PubMed2006

Nanostructured electrochemical DNA biosensors for detection of the effect of berberine on DNA from cancer cells.

Multi walled carbon nanotubes (MWNT) in dimethylformamide (DMF) or aqueous sodium dodecyl sulfate (SDS) solution, colloidal gold nanoparticles (GNP) in phosphate buffer solution (PBS), and a GNP-MWNT mixture in aqueous SDS solution have been investigated for chemical modification of a screen-printed carbon electrode used as the signal transducer of a dsDNA-based biosensor. Differential pulse voltammetry of the DNA redox marker Co[(phen)3]3+ and the guanine moiety anodic oxidation and cyclic voltammetry with K3[Fe(CN)6] as indicator revealed substantial enhancement of the response of the biosensor, particularly when MWNT in SDS solution was used. The biosensor was used in testing of berberine, an isoquinoline plant alkaloid with significant antimicrobial and anticancer activity. Berberine had a very strong, concentration-dependent, effect on the structural stability of DNA from the human cancer cells (U937 cells) whereas non-cancer cells were changed only when berberine concentrations were relatively high 75 and 50 microg mL(-1).

Berberine↗

PubMed2006

Biosensor incorporating cell barrier architectures for detecting Staphylococcus aureus alpha toxin.

Alpha toxin is a common virulent factor of Staphylococcus aureus and is believed to play crucial roles in pathogenicity induced by S. aureus. Alpha toxin is also known to induce permeability to endothelial cell monolayers in vitro due to the formation of interendothelial gaps. The present study is directed towards measuring alpha toxin using a whole-cell-based biosensor. The biosensor, consisting of a confluent monolayer of human umbilical vein endothelial cells (HUVECs) on a potassium ion-selective electrode, takes advantage of cell permeability dysfunction to detect the presence of small quantities of alpha toxin. When a confluent monolayer of cells was formed on the membrane surface, the response of the electrode toward the marker ion, potassium, was inhibited. Upon exposing this sensor to varying concentrations of alpha toxin for 20 min, an increase in sensor response to potassium was observed. The response thus obtained was indirectly related to the concentration of alpha toxin. The detection limit of this sensor for alpha toxin was found to be 0.1 ng/ml. Cell monolayers were stained with silver nitrate to quantify the formation of intercellular gaps as well as to study the effect of this toxin on HUVECs morphology. A strong positive correlation was observed between the response obtained from the biosensor and the area of the intercellular gaps. Silver staining also revealed the tendency of cells to round up upon being exposed to alpha toxin.

Bacterial Toxins↗

PubMed2006

Probing traces of hydrogen peroxide by use of a biosensor based on mediator-free DNA and horseradish peroxidase immobilized on silver nanoparticles.

A new electrochemical biosensor for determination of hydrogen peroxide (H(2)O(2)) has been developed by immobilizing horseradish peroxidase (HRP) on silver colloids (nanosilver) and use of a DNA-functionalized interface. In the presence of the DNA and the nanosilver the immobilized HRP gives a pair of well-defined redox peaks with an electron-transfer rate constant of 3.27 +/- 0.91 s(-1) in pH 7.0 PBS. The presence of DNA also provides a biocompatible microenvironment for enzyme molecules, greatly amplifies the amount of HRP molecules immobilized on the electrode surface, and improves the sensitivity of the biosensor. Under optimum conditions the biosensor has electrocatalytic activity in the reduction of hydrogen peroxide with linear dependence on H(2)O(2) concentration in the range 1.5 x 10(-6) to 2.0 x 10(-3) mol L(-1); the detection limit is 5.0 x 10(-7) mol L(-1) at a signal-to-noise ratio of 3. The K(app)(m) value of HRP in the composite membrane was found to be 1.62 mmol L(-1). These results suggest that the properties of the complex film, with its bioelectrochemical catalytic activity, could make it useful for development of bioelectronic devices and for investigation of protein electrochemistry at functional interfaces.

Biosensing Techniques↗

PubMed2000

Construction and analytical application of a biosensor based on stearic acid-graphite powder modified with sweet potato tissue in organic solvents.

A biosensor based on stearic acid-graphite powder modified with sweet potato (Ipomoea batatas (L.) Lam.) tissue as peroxidase source was constructed and applied in organic solvents. Several parameters were studied to evaluate the performance of this biosensor such as stearic acid-graphite powder and tissue composition, type and concentration of supporting electrolyte, organic solvents, water/organic solvent ratio (% v/v) and hydrogen peroxide concentration. After selection of the best conditions, the biosensor was applied for the determination of hydroquinone in cosmetic creams in methanol. At the peroxidase electrode hydroquinone is oxidized in the presence of hydrogen peroxide and the radical formed was reduced back electrochemically at -180 mV vs Ag/AgCl (3.0 mol L(-1) KCl). The reduction current obtained was proportional to the concentration of hydroquinone from 6.2 x 10(-5) to 1.5 x 10(-3) mol L(-1) (r = 0.9990) with a detection limit of 8.5 x 10(-6) mol L(-1). The recovery of hydroquinone from two samples ranged from 98.8 to 104.1% and an RSD lower than 1.0% for a solution containing 7.3 x 10(-4) mol L(-1) hydroquinone and 1.0 x 10(-3) mol L(-1) hydrogen peroxide in 0.10 mol L(-1) tetrabutylammonium bromide methanol-phosphate buffer solution (95:5% v/v) (n = 10) was obtained.

Antioxidants↗

PubMed2001

DNA electrochemical biosensors.

Disposable electrochemical DNA-based biosensors are reviewed; they have been used for the determination of low-molecular weight compounds with affinity for nucleic acids and for the detection of the hybridisation reaction. The first application is related to the molecular interaction between surface-linked DNA and the target pollutants or drugs, in order to develop a simple device for rapid screening of toxic or similar compounds. The determination of such compounds was measured by their effect on the oxidation signal of the guanine peak of calf thymus DNA immobilised on the electrode surface and investigated by chronopotentiometric analysis. The DNA biosensor is able to detect known intercalating compounds, such as daunomycin, polychlorinated biphenyls (PCBs), aflatoxin B1, and aromatic amines. Applicability to river and waste water samples is also demonstrated. Disposable electrochemical sensors for the detection of a specific sequence of DNA were realised by immobilising synthetic single-stranded oligonucleotides onto a graphite screen-printed electrode. The probes became hybridised with different concentrations of complementary sequences present in the sample. The hybrids formed on the electrode surface were evaluated by chronopotentiometric analysis using daunomycin as indicator of the hybridisation reaction. The hybridisation was also performed using real samples. Application to apolipoprotein E (ApoE) is described, in this case samples have to be amplified by PCR and then analysed by DNA biosensor. The extension of such procedures to samples of environmental interest or to contamination of food is discussed.

Apolipoproteins E↗