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At least 253 records · Page 14Linked to original sources

PubMed2001

Ultrasensitive optical DNA biosensor based on surface immobilization of molecular beacon by a bridge structure.

A novel biotinylated molecular beacon (MB) probe was developed to prepare a DNA biosensor using a bridge structure. MB was biotinylated at the quencher side of the stem and linked on a biotinylated glass cover slip through streptavidin, which acted as a bridge between MB and glass matrix. An efficient fluorescence microscope system was constructed to detect the fluorescence change caused by the conformation change of MB in the presence of complementary DNA target. The proposed biosensor was used to directly detect, in real-time, the target DNA molecules. The bridge immobilization method caused the proposed DNA biosensor to have a faster and more stable response. Under the optimal conditions, the newly developed DNA biosensor showed a linear response toward ssDNA in the range of 5-100 nM with a detection limit of 2 nM. It was interesting to note that the described biosensor was reproducible after being regenerated by urea.

Biosensing Techniques↗

PubMed2002

Development of a platinized and ferrocene-mediated cholesterol amperometric biosensor based on electropolymerization of polypyrrole in a flow system.

The preparation of a cholesterol amperometric biosensor using a platinized Pt electrode as a support for the electropolymerization of a polypyrrole film, in which cholesterol oxidase and ferrocene monocarboxylic acid (electron-transfer mediator) were co-entrapped, is described. All the biosensor preparation steps (platinization and electropolymerization) and the cholesterol determination take place in the same flow system. The presence of the mediator enhances the sensitivity and selectivity of the platinized biosensor without modifying the dynamic parameters of the response, and the platinized layer improves the operational lifetime of the mediated sensor. The sensitivity obtained was 88.51 nA mM(-1) and the limit of detection was 12.4 microM of cholesterol. The analytical properties of the biosensor for the flow-injection determination of cholesterol were studied and compared with those of other more simple amperometric biosensor configurations.

Biosensing Techniques↗

PubMed2005

An amperometric glucose biosensor based on glucose oxidase immobilized in electropolymerized poly(o-aminophenol) and carbon nanotubes composite film on a gold electrode.

An amperometric glucose biosensor is developed that is based on immobilization of glucose oxidase (GOD) in a composite film of poly(o-aminophenol) (POAP) and carbon nanotubes (CNT), which are electrochemically co-polymerized at a gold (Au) electrode. Because of the high surface per volume ratio and excellent electrical conductivity of CNT, the biosensor based on an Au/POAP/CNT/GOD electrode has lower detection limit (0.01 mM), larger maximum response current (0.24 mA cm(-2)) and higher sensitivity (11.4 mA M(-1) cm(-2)) than the values of the biosensor based on an Au/POAP/GOD electrode. Additionally, the biosensor shows fast response time, large response current, and good anti-interferent ability for ascorbic acid, uric acid and acetaminophen. Good reproducibility and stability of the biosensor are also observed.

Biosensing Techniques↗

PubMed2000

Development of a xylitol biosensor composed of xylitol dehydrogenase and diaphorase.

In preparation for the development of a xylitol biosensor, the xylitol dehydrogenase of Candida tropicalis IFO 0618 was partially purified and characterized. The optimal pH and temperature of the xylitol dehydrogenase were pH 8.0 and 50 degrees C, respectively. Of the various alcohols tested, xylitol was the most rapidly oxidized, with sorbitol and ribitol being reduced at 65% and 58% of the xylitol rate. The enzyme was completely inactive on arabitol, xylose, glucose, glycerol, and ethanol. The enzyme's xylitol oxidation favored the use of NAD+ (7.9 U/mg) over NADP+ (0.2 U/mg) as electron acceptor, while the reverse reaction, D-xylulose reduction, favored NADPH (7.7 U/mg) over NADH (0.2 U/mg) as electron donor. The K(m) values for xylitol and NAD+ were 49.8 mM and 38.2 microM, respectively. For the generation of the xylitol biosensor, the above xylitol dehydrogenase and a diaphorase were immobilized on bromocyan-activated sephallose. The gel was then attached on a dissolved oxygen electrode. In the presence of vitamin K3, NAD+ and phosphate buffer, the biosensor recorded a linear response to xylitol concentration up to 3 mM. The reaction was stable after 15 min. When the biosensor was applied to a flow injection system, optimal operation pH and temperature were 8.0 and 30 degrees C, respectively. The strengths and limitations of the xylitol biosensor are its high affinity for NAD+, slow reaction time, narrow linear range of detection, and moderate affinity for xylitol.

Biosensing Techniques↗

PubMed1999

Studies on biosensor to determine diacetyl.

We studied the purification of diacetyl reductase, the preparation of a biosensor, and its performance. With diacetyl reductase and reduced coenzyme I (NADH) co-immobilized as working membrane, NAD+/NADH produced in the course of diacetyl reduction was connected with Fe2+/Fe to build a biosensor. The biosensor could be used to determine diacetyl concentration within the range from 0.1 microgram/mL to 0.5 microgram/mL and the response time was less than two minutes, and its performance was stable within 9 days. The experiments showed that typical metal ions and organics in nominal concentration did not affect the performance of the biosensor, meanwhile, the interference of dissolved oxygen on the performance of biosensor and regeneration of coenzyme I (NADH) were solved to some extent.

Acetoin Dehydrogenase↗

PubMed2001

Silicon-based biosensors for rapid detection of protein or nucleic acid targets.

BACKGROUND: We developed a silicon-based biosensor that generates visual, qualitative results or quantitative results for the detection of protein or nucleic acid targets in a multiplex format. METHODS: Capture probes were immobilized either passively or covalently on the optically coated surface of the biosensor. Intermolecular interactions of the immobilized capture probe with specific target molecules were transduced into a molecular thin film. Thin films were generated by enzyme-catalyzed deposition in the vicinity of the surface-bound target. The increased thickness on the surface changed the apparent color of the biosensor by altering the interference pattern of reflected light. RESULTS: Cytokine detection was achieved in a 40-min multiplex assay. Detection limits were 4 ng/L for interleukin (IL)-6, 31 ng/L for IL1-beta, and 437 ng/L for interferon-gamma. In multianalyte experiments, cytokines were specifically detected with signal-to-noise ratios ranging from 15 to 80. With a modified optical surface, specificity was also demonstrated in a nucleic acid array with unambiguous discrimination of single-base changes in a 15-min assay. For homozygous wild-type and homozygous mutant samples, signal-to-noise ratios of approximately 100 were observed. Heterozygous samples yielded approximately equivalent signals for wild-type and mutant capture probes. CONCLUSIONS: The thin-film biosensor allows rapid, sensitive, and specific detection of protein or nucleic acid targets in an array format with results read visually or quantified with a charge-coupled device camera. This biosensor is suited for multianalyte detection in clinical diagnostic assays.

Biosensing Techniques↗

PubMed2002

[Biosensors in the pharmaceutical domain].

Biosensors are analytical devices which incorporate a biological component (enzyme, antibody, animal or plant cell, DNA fragments, lipids.) intimately connected to a physical transducer (electrode, optical fibre, vibrating quartz.). This dual configuration allows the study of a great variety of compounds of pharmaceutical interest which react with the biocomponent. The latter is selected depending on the application and the performance criteria requested. Biosensors are suitable for real time monitoring such as in bioreactors, and for the determination of various physiological and pharmacological parameters. Biosensors may be employed in home testing (glucose, lactate.), in hospitals (bedside testing, emergency, surgery, dialysis monitoring, etc.) in clinical laboratory analyses (immunoassays, DNA analysis.) and at research centres. Ideally, a biosensor should be easy to use, allowing direct analysis without sample pre-treatment. Measurements should be automatized and remote controlled. The biosensor may be miniaturized for single use or for implementation in sensor arrays. Applications to microenvironments (in vivo, single cell.) or discrete one shot decentralized tests may also considered.

Biosensing Techniques↗

PubMed2002

Use of biosensors to monitor the immune response.

Biosensor instruments, such as the BIACORE, are gaining popularity for analysing serum samples for the presence of antibodies. These instruments offer several advantages in the detection and subsequent characterization of clinically relevant antibodies generated in response to administration of therapeutic proteins. Much like other common immunoassay platforms, immobilized ligand is used to capture antibodies. Unlike conventional approaches, the ligand is immobilized to the surface of a biosensor chip, with detection based upon surface plasmon resonance. This assay platform, therefore, does not require reporter molecules such as enzymes, fluorochromes or radioisotopes that are common to conventional immunoassay methodologies. Additional desirable features of the biosensor platform include real-time detection of the binding of antibody to ligand (for kinetic measurements) as well as straightforward characterization of antibody isotype, specificity and relative concentration. This is all performed with minimum serum requirements (typically 10 microlitres per sample analysed) in a fully automated environment. The unique features of the biosensor instrument warrant that these assays are referred to as biosensor immunoassays to clearly distinguish them from more conventional immunoassay methodologies, such as ELISA.

Antibodies↗

PubMed2003

[Biosensors for continuous glucose and lactate monitoring].

Biosensors, and in particular glucose and lactate sensors, are being widely developed and a few have been registered for continuous and semi-continuous use. Three glucose sensors, a transcutaneous sensor (GlucoWatch), a needle sensor (MiniMed) and microdialysis sensor (GlucoDay) have recently been evaluated among diabetes patients. The precise relationship between the biosensor signal and blood glucose is still a problem. For example, the utility of the subcutaneously placed needle sensor to detect nocturnal hypoglycaemia has been shown to be limited. The best subcutaneous site for placing the sensor needs to be systematically investigated. The three types of sensors have only been tested for a 3-5 day period. The utility of the microdialysis (separate from a direct link to biosensors) sensors among diabetes patients was established over a 3-week period following subcutaneous implantation. Furthermore, biosensors are being developed to monitor lactate in preterm babies, and patients with ischaemia, sepsis, or threatened organ damage (e.g. heart and brain infarction). In view of the current progress it is expected that within 5 years biosensor technology will have developed far enough to be used in the management of diabetes and in intensive care units.

Adult↗

PubMed1992

Biosensors: a new realism.

For many years biosensors have been hailed as the solution to many analytical problems. There is general agreement that biosensors offer the potential for easy-to-use, low-cost, rapid analysis. With such versatile, economic, reliable and cheap analytical devices at their disposal, manufacturers in industries as diverse as pharmaceuticals, food and drink, medical diagnostics and defence must surely be reaping vast profits from their biosensor-based products? In fact, biosensors have made only a very modest impact and this article attempts to present a realistic review of their current commercial potential. Consideration is given to the features and benefits of biosensors, the potential application markets, the impact of legislation, the needs of the user and the real commercial potential in the light of these factors and the existing competition.

Biosensing Techniques↗

PubMed2004

[Study of biosensor technology on the detection of endotoxin-neutralizing materials].

OBJECTIVE: To explore the application of biosensor technology in the determination of endotoxin-neutralizing materials. METHODS: After mixing polymyxin B (PMB) with endotoxin in certain concentration, the neutralizing ratio of PMB to endotoxin was assessed by biosensor technique and limulus amebocyte lysate test respectively. The results from the two methods were compared. RESULTS: The neutralizing ratio of PMB to endotoxin as assessed by biosensor technology was 0.35 microg to 1 ng, while that by dynamic turbidimetric and chromogenic limulus amebocyte lysate (LAL) technique was 0.5 mg to 1 ng and 1 mg to 1 ng, respectively. The results obtained by biotechnology were similar to that by biosensor technique. CONCLUSION: Biosensor technology was an accurate, convenient and rapid method for the determination of potency of endotoxin-neutralizing materials.

Bacterial Proteins↗

PubMed2004

Optical lectin based biosensor as tool for bacteria identification.

Biosensor techniques are based on biospecific interaction between the biological parts of biosensor with the analyte. In biosensor construction, antibodies are usually used for the detection of analytes such as microorganism, because of very strong and highly specific interaction. The disadvantages of this assay are a long time needed for antibody isolation and purification as well as difficult regeneration of biosensor chip. The use of lectins instead of antibodies could solve these problems because a several hundred lectins are commercially available and their stability in standard buffers is better compared to monoclonal antibodies. While antibody can only be used to detect that antigen it was designed for, lectin as low affinity molecule may bind several different pathogens. Using the discriminative effect of an artificial neural network the application of a lectin array will compensate for the lower specificity. Microbial surfaces bear many of the sugar residues capable of interacting with lectins. The ability of lectins to react with microbial glycoconjugates means that it is possible to employ them as probes and sorbents for whole cells, mutants and numerous cellular constituents and metabolites, and it makes them useful tools for identification or typing of bacteria. Lectins are attractive reagents for the clinical diagnostic laboratory because of their diverse specificity, commercial availability, a wide range of molecular weights, and their stability in standard buffers. The construction of lectin biosensor could be an advantage method for detection of pathogenic bacteria.

Animals↗

PubMedDate not supplied

[Amperometric biosensor for lactate analysis in wines and grape must during fermentation].

The amperometric biosensor based on lactate oxidase for determination of lactate has been developed, and two methods of immobilization of lactate oxidase on the surface of industrial screen-printed platinum electrodes SensLab were compared. A sensor with immobilized in the Resydrol polymer lactate oxidase by the method of physical adsorption is characterized of narrow dynamic range and greater response value in comparison with a biosensor based on immobilised in poly(3,4-ethylenedioxythiophene) lactate oxidase by the method of electrochemical polymerization. Operational stability of the biosensor developed was studied and it was shown, that the immobilization method does not influence their stability. The analysis of the lactate in wine and during wine fermentation has been conducted. High correlation of the data obtained by means of amperometric lactate biosensor and a standard method of an ionic chromatography has been shown. The developed biosensor could be applied in the food industry for the control and optimization of the wine fermentation process, and quality control of wine.

Biosensing Techniques↗

PubMed1989

Biosensors. A new analytic technology for real-time, on-line biochemical monitoring.

A new technology is evolving that has the potential of improving patient management while substantially reducing the overall cost of health care. This new technology is based on biosensors, analytic microelectronic devices that use biologic detector molecules (e.g., antibodies, enzymes, receptor proteins, lectins, nucleic acids) as the sensing or signal transducing elements. An array of different biosensor configurations are under development, spurred on by recent advances in biotechnology and solid-state electronics. Although not all biosensors can detect their target analytes instantaneously, nor perform continuous measurements, certain biosensors embody both capabilities. Real-time, on-line biochemical monitoring will offer important information heretofore unavailable to the physician. It is also inevitable that biosensor-based instruments will decentralize patient testing, but telemetric systems can maintain the active and necessary involvement of the clinical pathologist.

Biosensing Techniques↗

PubMed1987

Technological advances in bedside monitoring: biosensors.

The need to monitor certain key biochemical parameters in hospitalized patients is driving the development of biosensors, a new class of medical device for real-time, on-line quantitative analysis. A biosensor is a microelectronic device that utilizes a biological molecule (eg, antibody, enzyme, or receptor) as the sensing or signal-transducing element. Biosensors can be configured into simple, rapid, and cost-effective laboratory devices that will allow the clinical pathologist to become even more responsive to the primary care physician. In those instances where measurements on discrete samples do not provide the required information, continuous monitoring with implantable biosensors could provide real-time data on levels of critical endogenous or exogenous substances. By hybridizing recent advances in transdermal substance collection with the analytical capabilities of biosensors, devices for continuous noninvasive monitoring at the bedside can be envisioned. The clinical pathologist can and should play a key role in the clinical evaluation and implementation of such technological advances.

Antibodies↗

PubMed1994

[Contribution of L lactate and amino-acid enzymatic biosensors for the analysis of Frey syndrome].

Twelve patients with Frey's syndrome after total parotidectomy for plemorphic adenoma were analysed using simultaneously 2 biosensors. Biosensors allowed for detection of L lactate and amino acid level on intact skin. The assay procedure and the results achieved with the simultaneous use of these 2 biosensors are presented. The L lactate biosensor appears to be an interesting tool for Frey's syndrome analysis. The sensibility of the amino acid biosensor is not sufficient enough to allow its use at time of Frey's syndrome analysis.

Amino Acids↗

PubMedDate not supplied

[Biosensor models based on potentiometric and amperometric transducers for use in medicine, biotechnology, and environmental monitoring (review)].

Various types of potentiometric and amperometric biosensors are characterized: microbial sensors with Gluconobacter oxydans cells with potentiometric (pH-sensitive field-effect transistor) and amperometric (Clark-type) electrodes for determining glucose; a potentiometric enzymatic electrode with butyrylcholinesterase, which is used in the biosensor designed to detect pesticides; immunosensors with pH-sensitive field-effect transistors which detect the herbicide 2, 4-D; a biosensor for human immunoglobulin G; biosensors with anaerobic bacteria Clostridium thermocellum; chemical and enzymatic sensors containing a photosensitive membrane for determining ammonium ions and urea; and amperometric microbial sensors prepared with Pseudomonas cells for determining naphthalene, biphenyl, and polychlorinated benzoates. Practical applications of the developed models of biosensors to medicine, biotechnology, and environmental monitoring are discussed.

Biosensing Techniques↗

PubMedDate not supplied

Survey of the 1998 optical biosensor literature.

The utilization of optical biosensors to study molecular interactions continues to expand. In 1998, 384 articles relating to the use of commercial biosensors were published in 130 different journals. While significant strides in new applications and methodology were made, a majority of the biosensor literature is of rather poor quality. Basic information about experimental conditions is often not presented and many publications fail to display the experimental data, bringing into question the credibility of the results. This review provides suggestions on how to collect, analyze and report biosensor data.

Bibliometrics↗