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At least 883 records · Page 49Linked to original sources

PubMed1997

In-line pressure-flow module for in vitro modelling of haemodynamics and biosensor validation.

An in-line pressure-flow module for in vitro modelling of haemodynamics and biosensor validation has been developed. Studies show that good accuracy can be achieved in the measurement of pressure and of flow, in steady and pulstile flow systems. The model can be used for development, testing and evaluation of cardiovascular-mechanical-electrical anlogue models, cardiovascular prosthetics (i.e. valves, vascular grafts) and pressure and flow biosensors.

Animals↗

PubMed1996

Detection of endotoxin using an evanescent wave fiber-optic biosensor.

The lipopolysaccharide endotoxin is the most powerful immune stimulant known and a causative agent in the clinical syndrome known as sepsis. Sepsis is responsible for more than 100,000 deaths annually, in large part due to the lack of a rapid, reliable, and sensitive diagnostic technique. This study describes the detection of LPS from E. coli at concentrations as low as 10 ng/mL, in 30 s using an evanescent wave fiber-optic biosensor. Polymyxin B, covalently immobilized onto the surface of the fiber-optic probe, selectively bound fluorescently labeled LPS. Unlabeled LPS was detected in a competitive assay format using labeled LPS for signal generation. The competitive assay format worked in both buffer and plasma with similar sensitivities. This method can be used with other LPS capture molecules such as antibodies, lectins, or antibiotics, to simultaneously detect LPS and to determine the LPS serotype. The LPS assay using the fiber-optic biosensor is applicable to both clinical and environmental testing.

Biosensing Techniques↗

PubMedDate not supplied

Improved biosensor for glucose based on glucose oxidase-immobilized silk fibroin membrane.

Based on glucose oxidase-immobilized silk fibroin membrane and oxygen electrode, the authors have developed an amperometric glucose sensor in flow-injection analysis. After the sensor was improved by the configuration of oxygen electrode and a temperature control system was added to the electrode body, its sensitivity, analytical precision, and stability were enhanced greatly. The authors first introduced a tailing inhibitor-ion pair reagent into a buffer system in the biosensor so as to eliminate all interference from hemacyte, macromolecules, and small mol wt charged species besides electroactive specie ascorbate in complex matrices. A considerably serious tailing of the biosamples, such as whole blood, plasma, serum, or urine on the sensor, based on enzyme electrode, entirely disappeared, their response times were shortened, and base lines became more smooth and stable. The glucose sensor has a broad range of linear response for glucose (up to 25.0 mmol/L) and a good correlation (gamma = 0.999) under conditions of control temperature 32.0 degrees C and 1.6 mL/min 0.02 mol/L phosphate buffer containing 0.5% tailing inhibitor (v/v). Recoveries of glucose in these biosamples are within the range of 93.71-105.88%, and its repeatabilities for determining glucose, repeated 100 times, human blood dilution 125 times, and serum 128 times, are 1.81, 2.48, and 2.91% (RSD), respectively. The correlation analysis for 200 serum samples showed that the correlation (gamma) is 0.9934 between the glucose sensor and Worthington method for determining serum glucose used conventionally in a hospital laboratory. Moreover, the enzyme membrane used in the biosensor can be stored for a long time (over 2 yr) and measured repeatedly over 1000 times for biosamples. The glucose sensor is capable of detecting over 60 biosamples/hr.

Animals↗

PubMed1996

Antigen-antibody binding kinetics for biosensors. Changes in the fractal dimension (surface roughness) and in the binding rate coefficient.

The diffusion-limited binding kinetics of antigen in solution to antibody immobilized on a biosensor surface is analyzed within a fractal framework. Changes in the fractal dimension, Df observed are in the same and in the reverse directions as the forward binding rate coefficient k. For example, an increase in the concentration of the isoenzyme human creatine kinase isoenzyme MB form (CK-MB) (antigen) solution from 0.1 to 50 ng/mL and bound to anti-CK-MB antibody immobilized on fused silica fiber rods leads to increases in the fractal dimension Df from 0.294 to 0.5080, and in the forward binding rate coefficient k from 0.1194 to 9.716, respectively. The error in the fractal dimension Df decreases with an increase in the CK-MB isoenzyme concentration in solution. An increase in the concentration of human chorionic gonadotrophin (hCG) in solution from 4000 to 6000 mIU/mL hCG and bound to anti-hCG antibody immobilized on a fluorescence capillary fill device leads to a decrease in the fractal dimension Df from 2.6806 to 2.6164, and to an increase in the forward binding rate coefficient k from 3.571 to 4.033, respectively. The different examples analyzed and presented together indicate one means by which the forward binding rate coefficient k may be controlled, that is by changing the fractal dimension or the "disorder' on the surface. The analysis should assist in helping to improve the stability, the sensitivity, and the response time of biosensors.

Antibodies↗

PubMed1995

Assembly of antibodies in lipid membranes for biosensor development.

An investigation of the incorporation of antibody in lipid films of a composition that has been used for biosensor preparation is reported. IgG that is incorporated into lipid monolayers prepared from 7:3 mixtures of dipalmitoyl phosphatidylcholine and dipalmitoyl phosphatidic acid is edge-active, and enters and penetrates the fluid region of the mixed-phase system when monolayers are held at low pressure (< 20 mN/m). It was found that there is an "exclusion pressure" observed in pressure-area (pi-A) curves that are collected for monolayers that contain antibody. This term refers to a specific threshold of lateral pressure (which is reached by monolayer compression) that can cause explusion of antibody from the interior of a membrane. Microscopic images of monolayers containing the fluorescent phospholipid nitrobenzoxadiazole dipalmitoyl phosphatidylethanolamine (NBD-PE), or antibody labeled with tetramethylrhodamine isothiocyanate (TRITC), were used to determine the structure of membranes, and the location of effects on structure caused by IgG. Ellipsometric measurements of lipid monolayers that were cast onto silicon wafers by the Langmuir-Blodgett method were used to study the thickness of monolayers and to investigate the structural changes that occurred at the "exclusion pressure." Both the use of fluorescent antigen and ellipsometry indicated that antibody binding activity was present and was dependent on compression pressure. The effects of pH and ionic strength of subphase, antibody concentration, incubation time, and lateral pressure have been examined. The results may indicate the conditions that can be used to improve the incorporation of active IgG for preparation of biosensors that are based on lipid membranes.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2005

Study on the therapeutic mechanism of the active principle of the Chinese drug Paeoniae Radix 801 through affinity biosensors IAsys plus quartz crystal microbalance.

OBJECTIVE: To study the targeted point and mechanism of the function of the blood-activating and stasis-removing Chinese drugs, Paeoniae Radix 801(PR801) in its cardiovascular protective effects and its specific binding with endothelin 1 (ET-1) as well as the dynamics of the two's interactive function by means of using affinity biosensors: IAsys Plus and quartz crystal microbalance (IAQCM). METHODS: ET-1 was immobilized on the surfaces of IAQCM by using the new surface modification methods. The PR801 in the solution was detected by modified substrates and the specific binding between PR801 and ET-1 was studied. RESULTS: The curves went up or down after adding PR801. There is specific binding between PR801 and ET-1. The bound mass were 0.458 ng/mm(2) and 133.54 ng/cm(2), respectively. There exists relatively good stability with these two methods. CONCLUSION: The affinity biosensors: IAQCM can be used to study the interaction mechanism between PR801 and ET-1, providing a new way to study the interaction mechanism of TCM. PR801 can bind ET-1 specifically in the experiments. Therefore, ET-1 is another target that PR801 can bind specifically besides thromboxane A(2).

Biosensing Techniques↗

PubMed1992

A biosensor for L-proline determination by use of immobilized microbial cells.

A biosensor to quantify L-proline within 10(-5)-10(-3) mole/L concentration is described. Immobilized Pseudomonas sp. cells grown in a medium containing L-proline as the only source of carbon and nitrogen were used to create the biosensor. The cells oxidized L-proline specifically consuming O2 and did not react with other amino acids and sugars. The change in oxygen concentration was detected with a Clark oxygen membrane electrode. The cells were immobilized by entrapment in polyvinyl alcohol (PVA) cryogel. The resultant biocatalyst had a high mechanical strength and retained its L-proline-oxidizing ability for at least two months.

Adenosine Triphosphate↗

PubMed2001

Analysing structure-function relationships with biosensors.

Elucidating the nature of the relationship between the structure and function of biomolecules remains one of the major challenges in biology. Biomolecules are dynamic entities that possess a variety of structures, and their functions at the molecular, cellular and organismic levels are quite different. Since there is no single causal link between structure and function, the search should be for correlations rather than causal relations. Biosensor instruments based on surface plasmon resonance are widely used for establishing correlations between the chemical structure of binding sites and their binding activity. Mutagenesis studies have shown that only a small percentage of the residues located in a binding site contribute to the binding energy. Since substitutions in residues located far away from the binding site are able to affect binding activity, this greatly complicates the rational design of proteins endowed with improved functions. However, biosensors can be used to determine and predict the influence of the chemical environment and of the structure of a ligand on binding kinetics.

Binding Sites↗

PubMed2002

Rapid detection of neurotoxic insecticides in food using disposable acetyicholinesterase-biosensors and simple solvent extraction.

The extensive use of pesticides to protect agricultural crops necessitates reliable tools for the detection of residues in food and water, thus ensuring environmental protection and consumer safety. Neuroinhibitors such as organophosphates and carbamates in particular, represent a potential hazard to human health. These compounds are frequently found in food, but conventional methods of analysis are limited as they are either time consuming or not sufficiently sensitive. As a result, a rapid and sensitive biosensor test based on AChE-inhibition was developed. The disposable AChE-biosensor was directly applied in solvent extracts of food samples using isooctane as extraction solvent. A complete assay could be performed in less than 2 h. Recovery rates of 84% were obtained in tests with spiked orange juice samples. Tests in food samples with a lower water content resulted in reduced recovery rates (44% for peach pap baby food). Phosphorothionate insecticides in food could be detected after direct oxidation with N-bromosuccinimide and solvent extraction. The assay displayed a detection limit of 2 microg/kg paraoxon, which was sufficient for the monitoring of maximum residue limits in food according to EU regulations.

Acetylcholinesterase↗

PubMed2002

A BOD biosensor based on a microorganism immobilized on an Al2O3 sol-gel matrix.

A novel BOD biosensor has been fabricated from a microbial membrane on an oxygen electrode; a porous inorganic Al2O3 sol-gel matrix was used to immobilize the yeast. Use of the sensor is convenient and rapid compared with the official BOD5 method. The gelation time required to form the microorganism membrane was less than 15 min. There was linear relationship between the response (sensor current) and BOD values ranging from 10-50 mg x L(-1). The lifetime of the BOD biosensor was more than 30 days at ambient temperature.

Aluminum Oxide↗

PubMed2002

Fiber-optic biosensors--an overview.

This article reviews progress and developments during the past five years in the field of optical fiber biosensors. Because of the expense and time constraints associated with modern laboratory analysis, there is a growing need for real-time, low-cost technology that can be used industrially, environmentally, and clinically, and to monitor food processing. Miniaturization, integrated systems, and multianalyte determination have become key aspects of sensor development and efforts in this direction will also be discussed, with some pointers to likely directions of future research in the area. The review will provide information about the analytical characteristics and applications of fiber-optic biosensors classified depending on the biorecognition element employed - enzymes, whole cells, antibodies, nucleic acids, and biomimetic polymers.

Biosensing Techniques↗

PubMed2002

A DNA-electrochemical biosensor for screening environmental damage caused by s-triazine derivatives.

An electrochemical DNA-biosensor has been used to investigate the interactions between DNA and members of a group of ten derivatives of 1,3,5-triazine herbicides: chloro-s-triazines (atrazine, propazine, terbutylazin, and cyanazin), thiomethyl-s-triazines (ametryn, prometryn, terbutryn, and simetryn), and methoxy-s-triazines (prometon and terbumeton). A UV spectrophotometric study of this group of herbicides was also undertaken. Of this group only cyanazin could be oxidized in aqueous solution using a glassy carbon electrode. Use of the electrochemical DNA-biosensor revealed the occurrence of a time-dependent interaction of all the herbicides with DNA, via the appearance of guanine, guanosine, and adenosine oxidation signals that correspond to DNA damage. Adduct formation between the herbicide and the DNA purine bases guanine and adenine is suggested as a mechanism.

Biosensing Techniques↗

PubMed2002

TiO2 sol-gel derived amperometric biosensor for H2O2 on the electropolymerized phenazine methosulfate modified electrode.

A novel hydrogen peroxide biosensor was developed based on the immobilization of horseradish peroxidase (HRP) in a TiO(2) sol-gel matrix on an electropolymerized phenazine methosulfate (PMS) modified electrode surface. Such membranes are of interest due to their high surface area, biological compatibility, and ease of fabrication. HRP entrapped in the TiO(2) matix was stable and retained its activity to a large extent. Cyclic voltammetry and amperometric measurements were employed to demonstrate the feasibility of electron transfer between immobilized HRP and the glassy carbon electrode via electropolymerized PMS. The influence of various experimental parameters such as operating potential, pH, temperature, and stability was investigated for optimum analytical performance. The biosensor provided a wide linear calibration range from 4.0x10(-6) M to 1.0x10(-3) M, with a detection limit of 8.0x10(-7) M at a signal-to-noise ratio of 3. The sensor retained 80% of its original activity after two months of operation.

Biosensing Techniques↗

PubMed2002

Carbon nanotube array-based biosensor.

Aligned multi-wall carbon nanotubes (MWNT) grown on platinum substrate are used for the development of an amperometric biosensor. The opening and functionalization by oxidation of the nanotube array allows for the efficient immobilization of the model enzyme, glucose oxidase. The carboxylated open-ends of nanotubes are used for the immobilization of the enzymes, while the platinum substrate provides the direct transduction platform for signal monitoring. It is also shown that carbon nanotubes can play a dual role, both as immobilization matrices and as mediators, allowing for the development of a third generation of biosensor systems, with good overall analytical characteristics.

Biosensing Techniques↗

PubMed2003

Carbon nanotube-enhanced electrochemical DNA biosensor for DNA hybridization detection.

A novel and sensitive electrochemical DNA biosensor based on multi-walled carbon nanotubes functionalized with a carboxylic acid group (MWNTs-COOH) for covalent DNA immobilization and enhanced hybridization detection is described. The MWNTs-COOH-modified glassy carbon electrode (GCE) was fabricated and oligonucleotides with the 5'-amino group were covalently bonded to the carboxyl group of carbon nanotubes. The hybridization reaction on the electrode was monitored by differential pulse voltammetry (DPV) analysis using an electroactive intercalator daunomycin as an indicator. Compared with previous DNA sensors with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics dramatically increased DNA attachment quantity and complementary DNA detection sensitivity. This is the first application of carbon nanotubes to the fabrication of an electrochemical DNA biosensor with a favorable performance for the rapid detection of specific hybridization.

Base Sequence↗

PubMed2003

A microfluidic biosensor based on nucleic acid sequence recognition.

The development of a generic semi-disposable microfluidic biosensor for the highly sensitive detection of pathogens via their nucleic acid sequences is presented in this paper. Disposable microchannels with defined areas for capture and detection of target pathogen RNA sequence were created in polydimethylsiloxane (PDMS) and mounted onto a reusable polymethylmethacrylate (PMMA) stand. Two different DNA probes complementary to unique sequences on the target pathogen RNA serve as the biorecognition elements. For signal generation and amplification, one probe is coupled to dye encapsulated liposomes while the second probe is coupled to superparamagnetic beads for target immobilization. The probes hybridize to target RNA and the liposome-target-bead complex is subsequently captured on a magnet. The amount of liposomes captured correlates directly to the concentration of target sequence and is quantified using a fluorescence microscope. Dengue fever virus serotype 3 sequences and probes were used as a model analyte system to test the sensor. Probe binding and target capture conditions were optimized for sensitivity resulting in a detection limit of as little as 10 amol microL(-1) (10 pmol L(-1)). Future biosensors will be designed to incorporate a mixer and substitute the fluorescence detection with an electrochemical detection technique to provide a truly portable microbiosensor system.

Base Sequence↗

PubMed2003

Biosensors for environmental pollutants and food contaminants.

This review article provides an overview of the most recent literature on biosensors for environmental pollutants and food contaminants. Due to the large number of publications, only papers published between 2000 and January 2003 were considered. Also, while not all of the published literature could be reviewed here, over 200 references are cited to provide a good overview of research undertaken in the last two years. Older publications are covered by a number of earlier review articles. This article provides an introduction into the field including specific consideration of the application areas, describes the typical biosensor assay format used, and is subsequently structured according to the biorecognition elements used (i.e., nucleic acids, enzymes, whole cells, tissue and whole organisms, antibodies and receptors, and biomimetic materials). In addition, a section on microbiosensing systems is provided. Since only very few microbiosensors with applications in environmental and food systems have been published, enabling technology is also covered in this article.

Biosensing Techniques↗

PubMed2004

Optical fiber-based biosensors.

This review outlines optical fiber-based biosensor research from January 2001 through September 2003 and was written to complement the previous review in this journal by Marazuela and Moreno-Bondi. Optical fiber-based biosensors combine the use of a biological recognition element with an optical fiber or optical fiber bundle. They are classified by the nature of the biological recognition element used for sensing: enzyme, antibody/antigen (immunoassay), nucleic acid, whole cell, and biomimetic, and may be used for a variety of analytes ranging from metals and chemicals to physiological materials.

Biosensing Techniques↗