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 793 records · Page 44Linked to original sources

PubMed2002

Real-time determination of telomerase activity in cell extracts using an optical biosensor.

A biosensoric approach has been developed to determine the activity of telomerase in tumor cell lysates. An optical sensor, the grating coupler, was used to monitor the association and dissociation of unlabeled compounds on the sensor surface in real time, by virtue of an evanescent field. An oligonucleotide was immobilized on the surface of the optical biosensor and linked with two other oligonucleotides by complementary sequences in an overlapping manner. The 3'-end of the last one carried the sequence of the telomeric substrate (TS) primer used for elongation by telomerase in the telomeric repeat amplification protocol (TRAP) assay. This primer sequence was phosphorothioate (PS)-modified, which is known to strongly increase the affinity to the primer binding site of telomerase protein and consequently the velocity of the telomerase reaction. We show that the PS primer binds to the modified biosensor and is elongated effectively by the telomerase from HL-60 cell lysates. A synthesis rate of 1 nucleotide/min was determined. The inhibitory effect of peptide nucleic acid (PNA) was shown by using immobilized TS. The velocity of the telomerase reaction was slowed down and the signal intensity was below the signal-to-noise ratio. Most nucleic acid detection systems use amplification steps such as polymerase chain reaction (PCR) to increase the amount of the probe. Since telomerase is a polymerase itself amplification of DNA by PCR is not required. Furthermore, no purification steps were required since all measurements were performed with crude cell extract.

Base Sequence↗

PubMedDate not supplied

Bioluminescent bacterial biosensors for the assessment of metal toxicity and bioavailability in soils.

A major factor governing the toxicity of heavy metals in soils is their bioavailability. Traditionally, sequential extraction procedures using different extractants followed by chemical analysis have been used for determining the biologically available fraction of metals in soils. Yet, the transfer of results obtained on non-biological systems to biological ones is certainly questionable. Therefore, bioluminescence-based bacterial biosensors have been developed using genetically engineered microorganisms, constructed by fusing transcriptionally active components of metal resistance mechanisms to lux genes from naturally bioluminescent bacteria like Vibrio fischeri for the assessment of metal toxicity and bioavailability in polluted soils. As compared to chemical methods, bacterial biosensors present certain advantages, such as selectivity, sensitivity, simplicity, and low cost. Despite certain inherent limitations, bacterial bioluminescent systems have proven their usefulness in soils under laboratory and field conditions. Finally, green fluorescent protein-based bacterial biosensors are also applicable for determining with high sensitivity the bioavailability of heavy metals in soil samples.

Aliivibrio fischeri↗

PubMed2005

A FRET-based calcium biosensor with fast signal kinetics and high fluorescence change.

Genetically encoded calcium biosensors have become valuable tools in cell biology and neuroscience, but some aspects such as signal strength and response kinetics still need improvement. Here we report the generation of a FRET-based calcium biosensor employing troponin C as calcium-binding moiety that is fast, is stable in imaging experiments, and shows a significantly enhanced fluorescence change. These improvements were achieved by engineering magnesium and calcium-binding properties within the C-terminal lobe of troponin C and by the incorporation of circularly permuted variants of the green fluorescent protein. This sensor named TN-XL shows a maximum fractional fluorescence change of 400% in its emission ratio and linear response properties over an expanded calcium regime. When imaged in vivo at presynaptic motoneuron terminals of transgenic fruit flies, TN-XL exhibits highly reproducible fluorescence signals with the fastest rise and decay times of all calcium biosensors known so far.

Animals↗

PubMed2005

Increased oxygen consumption rates in response to high glucose detected by a novel oxygen biosensor system in non-human primate and human islets.

In this study, we investigated the use of a novel oxygen biosensor system to detect changes in oxygen consumption rates (OCRs) by islets in response to glucose. Islets from non-human primate and human pancreata were seeded into an oxygen biosensor system microplate and exposed to basal (2.8 or 5.6 mM) or high (16.7 or 33.3 mM) glucose over either a long-term or a short-term culture. Our data clearly demonstrated that non-human primate islets cultured in high glucose conditions exhibited significant increases in OCRs over a 168 h extended culture period (P<0.05), which indicates an accelerated rate of beta-cell metabolism triggered by glucose over time. Significant increases in OCRs (P<0.01) were also attained in both non-human primate and human islets exposed to high glucose conditions in a 120 min short-term incubation period. OCRs exhibited by human islets exposed to different glucose concentrations correlated with insulin secretion (r(2)=0.7681, P<0.01). Moreover, the OCR stimulation index (i.e. OCR at high glucose/OCR at basal glucose) was significantly greater in human islets displaying high viabilities as opposed to islets exhibiting low viabilities (P<0.05). Together these data demonstrate that this novel oxygen biosensor system documents significant increases in islet oxygen consumption upon acute and chronic exposure to high glucose concentrations. Importantly, this methodology rapidly and robustly detects changes in OCRs by islets in response to high glucose stimulation that correlate well with the metabolic activities and functional viability of islets and clearly delineates significant differences in OCR stimulation index between high and low viability human islets, and therefore may prove to be an effective approach for quickly assessing the functional viability of islets prior to transplantation.

Animals↗

PubMed2004

Amperometric glucose biosensor based on mediated electron transfer between immobilized glucose oxidase and plasma-polymerized thin film of dimethylaminomethylferrocene on sputtered gold electrode.

We propose an electron transfer-mediated amperometric enzyme biosensor based on plasma-polymerized thin film of dimethylaminomethylferrocene (DMAMF) on a sputtered gold electrode. The DMAMF plasma-polymerized film is deposited directly onto the surface of the electrode under dry conditions. The resulting thin film not only has redox sites but also is extremely thin (approximately 20 nm), adheres well onto the substrate (electrode), has a flat surface and a highly-crosslinked network structure, and is hydrophilic in nature. Glucose oxidase is densely immobilized onto the surface of DMAMF plasma-polymerized film on the gold electrode. From the electrochemical measurement, the biosensor can cover the wide range of glucose concentration (1.3 - 81 mM) at +350 mV of applied potential. The current response of the glucose biosensor was decreased by less than 5% in an aerobic solution as compared to that in an anaerobic solution. These show that the DMAMF plasma-polymerized films play a role as the electron transfer mediators between the reaction center of enzyme and the electrode.

Biosensing Techniques↗

PubMed2004

Third-generation biosensors based on the direct electron transfer of proteins.

Recent progress in third-generation electrochemical biosensors based on the direct electron transfer of proteins is reviewed. The development of three generations of electrochemical biosensors is also simply addressed. Special attention is paid to protein-film voltammetry, which is a powerful way to obtain the direct electron transfer of proteins. Research activities on various kinds of biosensors are discussed according to the proteins (enzymes) used in the specific work.

Animals↗

PubMed2002

Selecting nucleic acids for biosensor applications.

In vitro selection can be used to generate nucleic acid binding species (aptamers) and catalysts (ribozymes) that can recognize a variety of molecules. Because nucleic acid function is largely derived from readily tabulated secondary structures, it has proven possible to engineer aptamers and ribozymes to function as biosensors. Labeling nucleic acids with reporter molecules has yielded simple antibody substitutes, but by relying on ligand-dependent conformational changes it has also proven possible to generate biosensors that can recognize and specifically report the presence of ligands in homogenous solution. It may prove possible to generate signaling aptamers and allosteric ribozymes (aptazymes) that are responsive to a large fraction of an organismal proteome or metabolome using automated methods. Nucleic acid biosensor arrays for non-nucleic acid targets could likely be generated with the same facility as DNA chips.

Base Sequence↗

PubMed2005

Carbon nanotubes (CNTs) for the development of electrochemical biosensors.

Carbon nanotube (CNT) is a very attractive material for the development of biosensors because of its capability to provide strong electrocatalytic activity and minimize surface fouling of the sensors. This article reviews our recent developments of oxidase- and dehydrogenase-amperometric biosensors based on the immobilization of CNTs, the co-immobilization of enzymes on the CNTs/Nafion or the CNT/Teflon composite materials, or the attachment of enzymes on the controlled-density aligned CNT-nanoelectrode arrays. The excellent electrocatalytic activities of the CNTs on the redox reactions of hydrogen peroxide, nicotinamide adenine dinucleotide (NADH), and homocysteine have been demonstrated. Successful applications of the CNT-based biosensors reviewed herein include the low-potential detections of glucose, organophosphorus compounds, and alcohol.

Alcohols↗

PubMed2005

Extended-range glucose biosensor via layer-by-layer assembly incorporating gold nanoparticles.

We report on a glucose oxidase (GOx)/polyelectrolyte (PE)/gold nanoparticle (AuNP) multilayer films that can be utilized as efficient glucose biosensors by layer-by-layer self-assembly method. Electrochemical impedance spectroscopy (EIS) and UV-visible spectroscopy were adopted to monitor the regular growth of the multilayer films. The role of gold nanoparticles integrated in the multilayer films not only increase the amount and activity of GOx, but also significantly improve the electron-transfer characteristics of the films. The performance of the multilayer films for sensing glucose could be tailored by controlling the gold nanoparticles loading in the film and the number of layers. A biosensor constructed by four poly(dimethyldiallylammonium chloride) (PDDA)/AuNP/PDDA/GOx multilayer films exhibited a wide linear calibration range from 0 to 60.0 mM with the detection limit of 3.0 microM for the detection of glucose. The dynamic range can be extended up to 120 mM. The biosensor has good stability and reproducibility.

Absorption↗

PubMed2005

Fabrication of a hydrogen peroxide biosensor based on a self-assemble composite oxide film.

A titania film with horseradish peroxidase (HRP) was immobilized on indium tin oxide (ITO) electrodes to act as a biosensor of hydrogen peroxide via the self-assembling and sol-gel route. The film was characterized by the atomic functional microscopy, electrochemical and UV-vis spectroscopy methods. The resulting biosensor exhibited fast amperometric response and good stability to hydrogen peroxide (H2O2). The linear range for H2O2 determination was from 2 x10(-6) to 1.45 x 10(-3) M, with a detection limit of 4 x10(-6) M based on S/N=3. The apparent Michaelis-Menten constant of the biosensor to H2O2 was estimated to be 1.5 mM, showing the HRP on the films had the higher biologic activities.

Biosensing Techniques↗

PubMedDate not supplied

Uses of biosensors in the study of viral antigens.

The introduction in 1990 of a new biosensor technology based on surface plasmon resonance has greatly simplified the measurement of binding interactions in biology. This new technology known as biomolecular interaction analysis makes it possible to visualize the binding process as a function of time by following the increase in refractive index that occurs when one of the interacting partners binds to its ligand immobilized on the surface of a sensor chip. None of the reactants needs to be labelled, which avoids the artefactual changes in binding properties that often result when the molecules are labelled. Biosensor instruments are well-suited for the rapid mapping of viral epitopes and for identifying which combinations of capturing and detector Mabs will give the best results in sandwich assays. Biosensor binding data are also useful for selecting peptides to be used in diagnostic solid-phase immunoassays. Very small changes in binding affinity can be measured with considerable precision which is a prerequisite for analyzing the functional effect and thermodynamic implications of limited structural changes in interacting molecules. On-rate (ka) and off-rate (kd) kinetic constants of the interaction between virus and antibody can be readily measured and the equilibrium affinity constant K can be calculated from the ratio ka/kd = K.

Antigens, Viral↗

PubMed1999

Development of a rapid response biosensor for detection of Salmonella typhimurium.

An integrated optic interferometer for detecting foodborne pathogens was developed. The interferometer is a planar waveguide with two thin antibody-coated channels of immunochemically selective agents that interact with antigen molecules. One channel is coated with antibody to Salmonella as a sample, and the other is coated with human immunoglobulin G as a reference channel by using reductive amination. Salmonella was introduced onto the sensing channels through the flow cell on the channels. Phase shift (pi) generated by refractive index variation, as determined by interfering the perturbed sample channel with an unperturbed reference channel and observing the fringe shift, was used for detection. Salmonella Typhimurium (heat-treated or boiled) was detected by binding to antibody against Salmonella common structural antigen immobilized on a silane-derived sensor surface at concentrations in the range of 1x10(5) to 1x10(7) CFU/ml. Salmonella (1x10(7) CFU/ml) mixed with Escherichia coli (1x10(7) CFU/ml) were readily detected without any decrease in sensitivity by the direct assay. Application of a sandwich assay with a second antibody or a gold-conjugated antibody increased the detection limit to 1x10(5) CFU/ml within a 10-min reaction time. Various methods for the immobilization of the capture antibody to the biosensor channels were compared. The greatest binding response was observed in a direct reductive amination method with a long reaction period and increased the detection limit of direct binding of Salmonella antigen to 1x10(4) CFU/ml. The biosensor was able to detect Salmonella Typhimurium in chicken carcass wash fluid originally inoculated at a level of 20 CFU/ml after 12 h of nonselective enrichment. The planar optic biosensor shows promise as a fast, sensitive, reliable, and economical means of detecting food pathogens in the future.

Animals↗

PubMed2003

Rapid detection of Escherichia coli O157:H7 inoculated in ground beef, chicken carcass, and lettuce samples with an immunomagnetic chemiluminescence fiber-optic biosensor.

A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia coli O157:H7 inoculated in ground beef, chicken carcass, and romaine lettuce samples. The biosensor consisted of a chemiluminescence reaction cell, a fiber-optic light guide, and a luminometer linked to a personal computer in conjunction with immunomagnetic separation. The samples inoculated with E. coli O157:H7 were first centrifuged and suspended in buffered peptone water and then incubated with anti-E. coli O157 antibody-coated magnetic beads and horseradish peroxidase (HRP)-labeled anti-E. coli O157 antibodies to form antibody-coated bead-bacterium-HRP-labeled antibody sandwich complexes. Finally, the sandwich complexes were separated from the samples in a magnetic field and reacted with luminol in the reaction cell. The number of E. coli O157:H7 cells was determined by collecting the HRP-catalyzed chemiluminescence signal from the bead surface through a fiber-optic light guide and measuring the signal with a luminometer. The chemiluminescence biosensor was specific for E. coli O157:H7 in samples containing other bacteria, including Salmonella Typhimurium, Campylobacter jejuni, and Listeria monocytogenes. The chemiluminescence signal was linear on a log scale from 10(2) to 10(5) CFU of E. coli O157:H7 per ml in samples. Detection could be completed within 1.5 h without any enrichment. The detection limits for ground beef, chicken carcass, and lettuce samples were 3.2 x 10(2), 4.4 x 10(2), and 5.5 x 10(2) CFU of E. coli O157:H7 per ml, respectively.

Animals↗

PubMed2000

Whole-blood glucose and lactate. Trilayer biosensors, drug interference, metabolism, and practice guidelines.

OBJECTIVE: To assess the effects of 30 of the most commonly used critical care drugs on measurements obtained with trilayer electrochemical biosensors on a reference analyzer (ABL625-GL), to determine metabolic changes in glucose and lactate in vitro, and to formulate guidelines for whole-blood analysis of these 2 analytes. DESIGN: Serial measurements were taken of changes in glucose and lactate levels caused by metabolism in whole blood in vitro over time. A parallel control study of drug interference with measurements of glucose and lactate in whole blood and of dose-response relationships in whole-blood samples and in plasma samples also was conducted. RESULTS: At room temperature, whole-blood metabolism decreased glucose levels -2.3% at 15 minutes, -4.6% at 30 minutes, and -6.4% at 45 minutes. Metabolism increased lactate levels 11.4% at 15 minutes, 20.6% at 30 minutes, and 26.7% at 45 minutes in vitro. Paired differences between drug-spiked and control samples were calculated to determine interference (corrected for metabolism). The threshold for determination of interference was +/-2 SD from within-day precision, equal to +/-0.18 and +/-0.10 mmol/L for glucose and lactate, respectively. Only mannitol (C(6)H(14)O(6)) interfered with glucose and lactate measurements. At a concentration of 24 mg/mL, mannitol decreased whole-blood glucose levels by an average of 0.711 mmol/L (12.8 mg/dL) and whole-blood lactate levels by 0.16 mmol/L (1.4 mg/dL). Mannitol interference with measurements may have resulted from suppression of hydrogen peroxide formation in the enzymatic reactions in the biosensors, repartitioning of water between erythrocytes and plasma, or from other mechanisms. CONCLUSIONS: Most critical care drugs had no significant effects on the trilayer electrochemical biosensors. Whole-blood analysis should be performed within 15 minutes for lactate and within 30 minutes for glucose because of metabolism in vitro. Mannitol effects on glucose measurements may be clinically significant in mannitol-induced acute renal failure and therefore should be considered for appropriate diagnosis and treatment of critically ill patients.

Biosensing Techniques↗

PubMed1998

A sensitive photosystem II-based biosensor for detection of a class of herbicides.

We have developed a biosensor for the detection of residual triazine-, urea- and phenolic-type herbicides, using isolated photosystem II (PSII) particles from the thermophilic cyanobacterium, Synechococcus elongatus, as biosensing elements. The herbicide detection was based on the fact that, in the presence of artificial electron acceptors, the light-induced electron transfer through isolated PSII particles is accompanied by the release of oxygen, which is inhibited by the herbicide in a concentration-dependent manner. The PSII particles were immobilized between dialysis membrane and the Teflon membrane of the Clark oxygen electrode mounted in a flow cell that was illuminated. Inclusion of the antibiotic chloramphenicol in the reaction mixtures prolonged, by 50%, the lifetime of the biosensor. The use of highly active PSII particles in combination with the flow system resulted in a reusable herbicide biosensor with good stability (50% of initial activity was still remaining after 35-h use at 25 degrees C) and high sensitivity (detection limit for diuron was 5 x 10(-10) M).

Biosensing Techniques↗

PubMed1995

Biosensor markets: opportunities and obstacles.

Currently, glucose sensing for the control of diabetes is the only high-volume market for biosensors. Yet, a variety of lower-volume niches are available for exploitation in medical diagnostics and the pharmaceutical and other industries. There are problems waiting for biosensor solutions, but the balance between market opportunities and technical and/or financial obstacles will control the future expansion of biosensor technology.

Biosensing Techniques↗

PubMed1999

Applications for the new electrochemiluminescent (ECL) and biosensor technologies.

Biosensor and electrochemiluminescent (ECL) assays are replacing enzyme-linked immunosorbent assays (ELISAs) at Schering-Plough as immunoassays of choice to monitor cytokine levels and detect anti-cytokine antibody responses during cytokine therapy. These new assays provide increased sensitivity and a better correlation with biological assays. Biosensor assays using the BIACORE 2000 (BIACORE, Uppsala, Sweden) are being adopted to support preclinical and clinical trials for the detection of antibodies capable of binding to IL-10 and IL-4. Significant advantages when using a biosensor assay are that real-time and label-free detection permit increased throughput and direct detection of binding interactions which enables detection of low affinity antibodies that are not detected by ELISA. The ECL assays using the ORIGEN Analyser (IGEN, Gaithersburg, MD) that we have implemented to replace existing ELISAs for quantification of serum IL-10 and serum interferon alfa levels are more sensitive and less subject to matrix effects. Data obtained during the validation of these assays are described.

Antibodies↗

PubMedDate not supplied

Determination of oxalate in urine, using an amperometric biosensor with oxalate oxidase immobilized on the surface of a chromium hexacyanoferrate-modified graphite electrode.

A novel enzymatic amperometric method is described for the determination of oxalic acid in urine. An amperometric biosensor was made by immobilizing oxalate oxidase on the surface of a chromium(III) hexacyanoferrate-modified graphite electrode by using a bovine serum albumin and glutaraldehyde cross-linking procedure. The enzyme biocatalyzes oxalate decomposition in the presence of oxygen into carbon dioxide and hydrogen peroxide. The oxalate concentration, which is proportional to the amount of hydrogen peroxide, was determined amperometrically by measuring the current resulting in the reduction of hydrogen peroxide at a very low working potential (0.05 V versus the Hg ¿Hg2Cl2¿ 3M KCl electrode), which minimized the influence of the possible interferences present in human urine. All experiments were performed with succinic buffer, pH 3.8, containing 0.1M KCl and 5.4mM ethylenediaminetetraacetic acid. In an aqueous solution of pure oxalic acid, the biosensor showed good linearity in a concentration range of 2.5-100 microM without the use of a dialysis membrane. For untreated urine samples, a high correlation (R2 = 0.9949) was obtained between oxalate concentrations added to urine samples and oxalate recoveries calculated for determinations with the described oxalate biosensor.

Biosensing Techniques↗