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 613 records · Page 34Linked to original sources

PubMed2006

Highly sensitive gold nanoparticles biosensor chips modified with a self-assembled bilayer for detection of Con A.

In this paper, an improved method for detection of Concanavalin A (Con A) with label-free optical biosensors is reported. 1-Dodecanethiol (DDT) was self-assembled onto gold nanoparticles which were deposited on glass slides, and then glycolipid molecules were inserted into dodecanethiol by physical interactions only. The recognition between Con A and carbohydrate was observed by UV-vis spectrophotometry. The absorption spectrum shifted when Con A was bound to the sugar residues of glycolipids immobilized onto nanogold slides, while almost no spectrum change was observed when another nonspecific protein molecule met the nanogold slides. The self-assembled bilayer on nanogold substrates had very high sensitivity for Con A, the minimum detection concentration of Con A can be down to 0.1 nM. In addition to the ultra sensitivity for investigating carbohydrate-lectin interaction, the self-assembled bilayer structure, is expected to replace many receptors which require time-consuming organic syntheses for the fixation to the transducer. The simplicity and sensitivity of this biosensor architecture once again show the prospect of nanogold application in biosensor.

Biosensing Techniques↗

PubMed2006

Development of a micro-planar amperometric bile acid biosensor for urinalysis.

The determination of bile acid concentration in urine is useful for the screening and diagnosis of various hepatobiliary diseases. Currently, there is no concise method to determine bile acid concentration in urine. This study describes a bile acid biosensor fabricated by electrochemical technique for urinalysis. The micro-planar electrodes employed for the study consisted of a working electrode (platinum), a counter electrode (platinum) and a reference electrode (silver/silver chloride (Ag/AgCl)). The sensor chip was coated with Nafion using a spin-coater in order to both eliminate many interference species in urine and achieve long-term stability of the reference electrode. Nafion coating allowed the sensor chip to prevent the electrode reaction from interference species in urine, because it is charged negative strongly (Nafion contains sulfonic acid group). Three enzymes (bile acid sulfate sulfatase: BSS, beta-hydroxysteroid dehydrogenase: beta-HSD, and NADH oxidase: NHO) were immobilized by glutaraldehyde (GA: cross-linker) onto the sensor chip, because the immobilization of enzymes by GA is simple and commonly carried out. The sensor chip was able to detect bile acid in buffer solution. The optimum enzyme ratio immobilized onto the sensor chip was BSS:beta-HSD:NHO=4:4:20 U/1 chip. There was a relationship between the concentration of bile acid and the response current value. The dynamic range of the sensor chip was 2-100 microM for bile acid. Additionally, bile acid in the urine specimen could be detected using this bile acid biosensor. We present a simple and rapid bile acid biosensor with high sensitivity and high reproducibility.

Bile Acids and Salts↗

PubMed2006

High efficiency Hall effect micro-biosensor platform for detection of magnetically labeled biomolecules.

Detection of magnetically labeled biomolecules using micro-Hall biosensors is a promising method for monitoring biomolecular recognition processes. The measurement efficiency of standard systems is limited by the time taken for magnetic beads to reach the sensing area of the Hall devices. Here, micro-current lines were integrated with Hall effect structures to manipulate the position of magnetic beads via field gradients generated by localized currents flowing in the current lines. Beads were accumulated onto the sensor surface within seconds of passing currents through the current lines. Real-time detection of magnetic beads using current lines integrated with Hall biosensors was achieved. These results are promising in establishing Hall biosensor platforms as efficient and inexpensive means of monitoring biomolecular reactions for medical applications.

Biosensing Techniques↗

PubMed2006

Coupled waveguide-surface plasmon resonance biosensor with subwavelength grating.

This study develops a coupled waveguide-surface plasmon resonance (CWSPR) biosensor with a subwavelength grating structure for the real-time analysis of biomolecular interactions. In the proposed optical metrology system, normally incident white light is coupled into the waveguide layer through the subwavelength grating structure thereby enhancing the wave vector which excites the surface plasmons on the metal sensing surface. The proposed CWSPR biosensor not only retains the same sensing sensitivity as that of a conventional surface plasmon resonance device, but also yields a sharper dip in the reflectivity spectrum and therefore provides an improved measurement precision. Moreover, the metrology setup overcomes the limitations of the conventional Kretschmann attenuated total reflection approach and is less sensitive to slight variations in the angle of the incident light. The experimental results confirm that the current CWSPR biosensor provides a straightforward yet powerful technique for real-time biomolecular interaction analysis.

Biopolymers↗

PubMed2007

Pesticide detection with a liposome-based nano-biosensor.

Monitoring of the organophosphorus pesticides dichlorvos and paraoxon at very low levels has been achieved with liposome-based nano-biosensors. The enzyme acetylcholinesterase was effectively stabilized within the internal nano-environment of the liposomes. Within the liposomes, the pH sensitive fluorescent indicator pyranine was also immobilized for the optical transduction of the enzymatic activity. Increasing amounts of pesticides lead to the decrease of the enzymatic activity for the hydrolysis of the acetylcholine and thus to a decrease in the fluorescent signal of the pH indicator. The decrease of the liposome biosensors signal is relative to the concentration of dichlorvos and paraoxon down to 10(-10)M levels. This biosensor system has been applied successfully to the detection of total toxicity in drinking water samples. Also a colorimetric screening device for pesticide analysis has been evaluated.

Biosensing Techniques↗

PubMed2007

Glucose biosensor based on immobilization of glucose oxidase in poly(o-aminophenol) film on polypyrrole-Pt nanocomposite modified glassy carbon electrode.

Novel Pt nanoclusters embedded polypyrrole nanowires (PPy-Pt) composite was electrosynthesized on a glassy carbon electrode, denoted as PPy-Pt/GCE. A glucose biosensor was further fabricated based on immobilization of glucose oxidase (GOD) in an electropolymerized non-conducting poly(o-aminophenol) (POAP) film that was deposited on the PPy-Pt/GCE. The morphologies of the PPy nanowires and PPy-Pt nanocomposite were characterized by field emission scanning electron microscope (FE-SEM). Effect of experimental conditions involving the cycle numbers for POAP deposition and Pt nanoclusters deposition, applied potential used in glucose determination, temperature and pH value of the detection solution were investigated for optimization. The biosensor exhibited an excellent current response to glucose over a wide linear range from 1.5 x 10(-6) to 1.3 x 10(-2)M (r=0.9982) with a detection limit of 4.5 x 10(-7)M (s/n=3). Based on the combination of permselectivity of the POAP and the PPy films, the sensor had good anti-interference ability to ascorbic acid (AA), uric acid (UA) and acetaminophen. The apparent Michaelis-Menten constant (K(m)) and the maximum current density (I(m)) were estimated to be 23.9 mM and 378 microA/cm(2), respectively. In addition, the biosensor had also good sensitivity, stability and reproducibility.

Biosensing Techniques↗

PubMed2006

Glucose microfluidic biosensors based on immobilizing glucose oxidase in poly(dimethylsiloxane) electrophoretic microchips.

Here we reported a novel microfluidic biosensor with an on-column immobilized enzyme microreactor. The fabrication approach of this biosensor is simple and the enzyme microreactors with controlled sizes can be placed at any desired position on the microchip. Taking glucose oxidase (GOx) as an example, electroosmotic flow (EOF) as a driving force and amperometry as a detection method, the performance of biosensors were modulated by changing the length of enzyme reactor from 0.5 cm to 3 cm, and the linear ranges were changed from 0-8.0 mM to 0-30.0 mM with the detection limits from 42 microM to 6.5 microM. The enzyme reactor remained its 65% activity after 23 days storage. It also showed good anti-interference ability and was used to quantify glucose in human serum samples.

Biosensing Techniques↗

PubMed2003

Biosensor profiling of molecular interactions in pharmacology.

Techniques employed to profile the pharmacological properties of a molecule in vitro normally require some type of radio-, enzymatic- or fluorescent-labeling of the ligand and/or the receptor. In contrast, biosensor techniques do not require labeling, and they allow virtually any complex to be screened with minimal assay development. Scientists in both academia and industry are now using biosensors in areas that encompass almost all sectors of drug discovery, diagnostics and the life sciences. Assays have been developed for the analysis of small molecules, proteins, oligonucleotides, bacteriophage, viruses, bacteria and cells. In addition, novel biosensor applications are being developed for the predictive profiling of key pharmacokinetic parameters of a molecule (adsorption, distribution, metabolism, excretion and toxicity).

Animals↗

PubMed2005

Construction of an extended range whole-cell tetracycline biosensor by use of the tet(M) resistance gene.

An extended range whole-cell tetracycline biosensor strain was constructed by insertion of the tet(M) gene, encoding tetracycline resistance by ribosomal protection, into plasmid pTGFP2, which contains a transcriptional fusion between a tetracycline regulated promoter and the green fluorescent protein gene. Tetracycline, oxytetracycline, chlortetracycline and minocycline all effectively induced the resulting Escherichia coli MC4100/pTGM biosensor and similar dose-response characteristics were recorded by flow cytometry for all four compounds. The novel tetracycline biosensor was responsive to drug concentrations ranging from below 5 ngml(-1) to 16 microgml(-1), which represents a significant improvement of the original version.

Bacterial Proteins↗

PubMed2004

Electrochemical impedance behavior of DNA biosensor based on colloidal Ag and bilayer two-dimensional sol-gel as matrices.

A novel method for fabrication of DNA biosensors has been developed by means of self-assembling colloidal Ag (Ag) to a thiol-containing sol-gel network. The thiol groups of 3-mercaptopropyltrimethoxysilane (MPTS) serve as binding sites for the covalent attachment to gold electrode surface. Then the one-dimensional network of silane unites (1dMPTS) was combined together into a two-dimensional sol-gel network (2dMPTS) by dipping into aqueous NaOH. The second silane layer (B2dMPTS) was formed by immersing electrodes back into the MPTS solution overnight, and then the Ag nanoparticles were chemisorbed onto the thiol groups of the second silane layer. Finally, the mercapto oligonucleotide was self-assembled onto the surface via the Ag nanoparticles. The modified process was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). In addition, we utilized the impedance spectroscopy as a platform for DNA sensing assay. The factors influencing the performance of the resulting biosensor were studied in detail. The linear range of the biosensor was from 8.0 x 10(-9) to 1.0 x 10(-6) M with a detection limit of 4.0 x 10(-9) M at 3sigma. In addition, the experiment results indicate that oligonucleotide immobilized on this way exhibits a good sensitivity and selectivity, high stability and a long-term maintenance of bioactivity.

Binding Sites↗

PubMed2004

Covalent immobilization of proteins for the biosensor based on imaging ellipsometry.

In the development of biosensors, the immobilization of biomolecules at interfaces played a crucial role. The feasibility of using 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (Glu) to modify silicon surface to immobilize covalently protein for immunoassay with the biosensor based on imaging ellipsometry was investigated. The higher density and stability of human IgG layer could be obtained on the silicon surface modified with APTES and Glu than that on the silicon surface modified with dichlorodimethylsilane (DDS). The human IgG molecules immobilized covalently on APTES-Glu surface bound more anti-IgG molecules than that on DDS surface, which indicated that the human IgG molecules could maintain higher binding capability on APTES-Glu surface. Tween 20 was able to block the undesirable adsorption on APTES-Glu surface, and also enhanced the recognition between human IgG and its antibody on both APTES-Glu and DDS surfaces. The combination of this protein covalent immobilization and the biosensor has the potential to be developed into a fast, simple immunoassay technique.

Antibody Affinity↗

PubMed2007

Application of lactate amperometric sol-gel biosensor to sequential injection determination of L-lactate.

This work describes the construction and evaluation of lactate sol-gel biosensors to accomplish the determination of lactate in pharmaceutical products. Lactate oxidase was incorporated in a porous sol-gel film placed onto a platinum-based electrode. Acid and basic catalysis were assessed. When coupled to a sequential injection system (SIA) the biosensor, based on (3-aminopropyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane, deionised water, polyethylene glycol 6000 and acid catalyst, presented a range of linearity of 5x10(-5) to 5x10(-3)M. The analytical usefulness of the developed biosensor was evaluated through analysis of commercial pharmaceutical products containing lactate with a sampling rate of 40 samples h(-1). The enzyme remained active for at least 30 days, enabling about 700 determinations without sensitivity decrease.

Biosensing Techniques↗

PubMed2006

Characterization of a laminar flow cell for the prevention of biosensor fouling.

A flow cell using dual parallel laminar flows was designed and fabricated with the aim to prevent biosensor fouling. Y-shaped entrances allowed the introduction of sample and electrolyte streams, with the electrolyte serving as a mobile protective layer near the biosensor. Potassium permanganate was used to quantify the diffusion in the flow cell. Optical intensity analysis of potassium permanganate along a series of transverse lines across the flow cell was carried out under different flow conditions. It was found that the error function, erf(y/[square root](Dt)), where y was the position along the transverse line, D the diffusion coefficient of the solute and t was the time, gave reasonable approximation to the diffusion of potassium permanganate in the cell. The diffusion coefficient of potassium permanganate was determined in stop-flow measurements and the value, D=4.0 x 10(-5)cm(2)/s, agreed to previously reported values. Velocity distribution in the flow cell was simulated numerically to reveal the development of two inflows into one single laminar flow. Results from the study provided preliminary data on solute diffusion characteristics in the flow cell and supported the working principle of laminar flow cells in preventing biosensor fouling.

Biosensing Techniques↗

PubMed2006

Non-invasive optical biosensor for assaying endogenous G protein-coupled receptors in adherent cells.

INTRODUCTION: Screening drugs against G protein-coupled receptors (GPCRs) - the single largest family of drug targets in the human genome - is still a major effort in pharmaceutical and biotech industries. Conventional cell-based assays generally measure a single cellular event, such as the generation of a second messenger or the relocation of a specific protein target. However, manipulation or engineering of cells is often a prerequisite for these technologies to achieve desired sensitivities. The present study is focused on the use of non-invasive and manipulation-free optical biosensors for assaying endogenous GPCRs in adherent cells. METHODS: Resonant waveguide grating (RWG) biosensor was applied to manifest ligand-induced dynamic mass redistribution (DMR) within the bottom portion of adherent cell layer. The DMR signatures mediated through the activation of several endogenous GPCRs in cells were characterized. Endogenous receptor panning was examined at cell system level by using a panel of agonists known to activate many GPCRs, and also at family receptor level by determining the efficacies of a set of family-specific agonists. RESULTS: Three major types of optical signatures were identified; each was correlated with the activation of a class of GPCRs, depending on the G protein with which the receptor is coupled (i.e., G(q), G(s) and G(i)). The characteristics of DMR signals, mostly the amplitude and kinetics of a DMR event, were dependent on the doses of agonists and the expression levels of endogenous receptors. All three classes of endogenous receptors were found in human epidermoid carcinoma A431 cells. Interestingly, the dose-dependent switching from one type of DMR signal to another was observed for several GPCR agonists examined. A small panel of P2Y receptor agonists exhibited distinct efficacies in three cell lines examined. DISCUSSIONS: The RWG biosensors were applicable to study the activation of endogenous GPCRs. Like second messengers or gene expression, the DMR signals obtained could be considered as novel and quantifiable physiological responses of living cells mediated through GPCRs and used for studying receptor biology.

Animals↗

PubMed2006

Microbial sensors for small molecules: development of a mevalonate biosensor.

We describe a novel biosensor strain for detection and quantification of a small molecule, mevalonate. The biosensor strain is an Escherichia coli mevalonate auxotroph that expresses the green fluorescent protein and reports on the mevalonate concentration in the growth medium through a change in growth rate. A model describing the growth rate dependence on mevalonate was developed in order to use the biosensor strain for high-throughput screening (HTS) and quantitative measurement of mevalonate in the extracellular environment. In general, this method should be applicable to the quantification of any small molecule for which an auxotroph can be developed and will be useful for HTS of evolved metabolic pathways for which there is no readily available screen or selection.

Aldose-Ketose Isomerases↗

PubMed2005

Piezoelectric biosensors: strategies for coupling nucleic acids to piezoelectric devices.

The development of a piezoelectric biosensor based on nucleic acids interaction is presented focusing on the methodology for probe immobilization. This is a key step in any DNA biosensor development. Often, the detection limits and, in general, the analytical performances of the biosensor can be improved by optimizing the immobilization of the receptor on the transducer surface. DNA must be attached to the solid support, retaining native conformation, and binding activity. This attachment must be stable over the course of a binding assay and, in addition, sufficient binding sites must be presented to the solution phase to interact with the analyte. In this paper, the optimization of the coating of the gold quartz crystal surface, to immobilize an oligonucleotide probe, is reported. Two immobilization procedures are illustrated in details with a comparison regarding the immobilization of the probe, the detection of the hybridization reaction, and the possibility of regeneration. The two procedures are based on the use of biotinylated or thiolated DNA probes. Specific applications will be also presented.

Biosensing Techniques↗

PubMed2005

A "do-it-yourself" array biosensor.

We have developed an array biosensor for the simultaneous detection of multiple targets in multiple samples within 15-30 min. The biosensor is based on a planar waveguide, a modified microscope slide, with a pattern of small (mm2) sensing regions. The waveguide is illuminated by launching the emission of a 635 nm diode laser into the proximal end of the slide via a line generator. The evanescent field excites fluorophores bound in the sensing region and the emitted fluorescence is measured using a Peltier-cooled CCD camera. Assays can be performed on the waveguide in multichannel flow chambers and then interrogated using the detection system described here. This biosensor can detect many different targets, including proteins, toxins, cells, virus, and explosives with detection limits rivaling those of the ELISA detection system.

Biosensing Techniques↗

PubMed2003

Optical imaging fiber-based live bacterial cell array biosensor.

A live cell array biosensor was fabricated by immobilizing bacterial cells on the face of an optical imaging fiber containing a high-density array of microwells. Each microwell accommodates a single bacterium that was genetically engineered to respond to a specific analyte. A genetically modified Escherichia coli strain, containing the lacZ reporter gene fused to the heavy metal-responsive gene promoter zntA, was used to fabricate a mercury biosensor. A plasmid carrying the gene coding for the enhanced cyan fluorescent protein (ECFP) was also introduced into this sensing strain to identify the cell locations in the array. Single cell lacZ expression was measured when the array was exposed to mercury and a response to 100nM Hg(2+) could be detected after a 1-h incubation time. The optical imaging fiber-based single bacterial cell array is a flexible and sensitive biosensor platform that can be used to monitor the expression of different reporter genes and accommodate a variety of sensing strains.

Adenosine Triphosphatases↗