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Biomedical subjects

I Karube

Publications and source records attributed to I Karube.

At least 19 recordsLinked to original sources
PubMed1992

Ultramicrobiosensors for monitoring of neurotransmitters.

Carbon fiber electrodes are used to construct ultramicrobiosensors with 7-15 microns diameter. Electrochemical operations for preelectrolysis and measuring were examined for sensitive determination of hydrogen peroxide. Determination limit was 0.1 microM of hydrogen peroxide. Reproducible determination of hydrogen peroxide is possible even in samples containing albumin protein. A micro-acetylcholine sensor was fabricated by immobilizing acetylcholine esterase and choline oxidase on the carbon fiber by entrapment with PVA-SbQ. This sensor gave a linear calibration plot for the range from 0.1 to 1.0 mM with a linear correlation coefficient of 0.9842. A micro-glutamate sensor consisted of a platinized carbon fiber disk electrode modified with immobilized glutamate oxidase membrane. This sensor gave a linear calibration for the range 2 microM to 1.2 mM. Release of glutamate in the cerebellar cortex was detected after potassium stimulation.

Acetylcholine↗
PubMed1992

Bioluminescence detection system of mutagen using firefly luciferase genes introduced in Escherichia coli lysogenic strain.

A rapid and convenient microbial sensing system for mutagens was developed based upon the induction of prophage from Escherichia coli lysogenic strain and bioluminescence. The system consisted of lysogenic E. coli encoding firefly luciferase genes and a photodetection system. Measurement of mutagen mitomycin C was achieved by measuring the luminescence intensity emitted from E. coli lysogenic strain for the recombinant phage in the presence of luminescence substrates. Approximately 1 h after addition of mitomycin C, the luminescence began to be observed, and 3 h after, it attained a level of 2 times greater than that of 1 h. Irradiation with ultraviolet light also produced light based on induction of phage from the E. coli lysogenic strain for the recombinant phage. On the other hand, when nonmutagenic toxic compounds like sodium azide were added to the reaction medium, luminescence was not observed. Mitomycin C could be detected within 1 h with this sensing system, at concentrations down to 10(2) ng/assay.

Bacteriophage lambda↗
PubMed1992

Application of a novel apparatus, the quartz chemical analyzer, to the determination of endotoxin in blood.

A novel apparatus called a quartz chemical analyzer (QCA) has been developed using a quartz crystal resonator. This apparatus measures sample viscosity changes based on resonant frequency changes of the quartz crystal. The apparatus was used to determine bacterial endotoxin concentrations by monitoring the gelation reaction of Limulus amebocyte lysate. The QCA determined endotoxin concentrations with good accuracy and reproducibility in the range of 0.001-3 EU/ml for endotoxin standard (JP XII). For endotoxin determination in human whole blood and plasma samples, the inhibitory reaction was eliminated by pretreatment of a fourfold dilution at 60 degrees C and incubation for 30 min. There are many advantages of the QCA method compared with the turbidimetric and chromogenic methods. For example, QCA can measure sample viscosity changes with high sensitivity and accuracy because QCA detects minor resonant frequency changes and the frequency data give a numerical value for easy quantitation. QCA can examine turbid samples, and the required quantities of samples and reagents are small, since the quartz crystal detects sample viscosity changes directly. The endotoxin determination time may be shortened by raising the reaction temperature, and QCA can detect other types of coagulation reactions.

Antithrombin III↗
PubMed1992

A biocompatible needle-type glucose sensor based on platinum-electroplated carbon electrode.

A biocompatible needle-type glucose sensor with a 3-electrode configuration was constructed. A platinum-electroplated carbon stick was used as the working electrode, Ag/AgCl as the reference electrode, and a disposable hypodermic needle made of stainless steel as the counter electrode. A Nafion membrane, an immobilized glucose oxidase (GOD) membrane, and a biocompatible membrane with diffusion-limiting effect were coated successively onto the working electrode. The sensor showed a rapid response (< 120 s in batch operation), good reproducibility (RE < 3%), good stability (over 36 h in control serum), a wide dynamic range (5-600 mg/dL glucose), and superior biocompatibility. It was used to determine glucose in serum. The data obtained from the sensor showed good agreement with that from a clinical autoanalyzer (R > 0.95).

Biocompatible Materials↗
PubMed1992

A novel microbial sensor using luminous bacteria.

A novel microbial sensor system that uses luminous bacteria was developed for the determination of both glucose and toxic compounds. The sensor system consisted of a membrane with luminous bacteria immobilized upon it and a photomultiplier. Measurements were based on the in vivo intensity of the light emitted by the bacteria, as this is affected by their environment. A linear relationship was observed between increased luminescence and concentrations of glucose between 0.05 mM and 0.55 mM. The relative standard deviation was 10% for 0.55 mM glucose (n = 10). Toxic compounds such as benzalkonium chloride, sodium dodecyl sulphate and chromium(VI) were also detected by measuring the decrease in luminescence in their presence.

Bacteria↗
PubMed1992

Biosensors and flow injection analysis.

Combining flow injection analysis with a biosensor is a novel biosensing process which has allowed speedy and accurate analysis. Diagnostic analysis is the most important application for biosensing flow injection analysis, but other applications include bioprocess monitoring, analysis of food and agricultural products, as well as environmental analysis. In addition, the analysis of compounds, such as explosives and abused drugs, and monitoring of Salmonella, the microorganism that causes food poisoning, have been reported.

Animals↗
PubMed1992

[Development and application of biosensors for medical field].

Methods for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods, based on specific enzyme-catalyzed reactions. However, because of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine a single compound in a biological fluid directly without need for a prior separation step. Therefore, in the past several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported.

Biomedical Engineering↗
PubMed1992

[Biosensors and clinical analysis].

Method for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods based on specific enzyme-catalyzed reactions. However, on account of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine directly a single compound in a biological fluid without need for a prior separation step. Therefore, in several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported. In the near future, an artificial pancreas fabricated by micromachine technology will be developed.

Biosensing Techniques↗
PubMed1991

Amplification immunoassay for the determination of hepatitis B surface antigen.

A sensitive sandwich immunoassay for the determination of Hepatitis B surface antigen (HBs) was developed, using a cascade system of Limulus amebocyte lysate as a signal amplification system. Lipopolysaccharide (LPS) was conjugated to anti-HBs antibody. Anti-HBs antibody was adsorbed to polystyrene beads. First, HBs were reacted to solid phase anti-HBs antibody (a-HBs). After the reaction, the beads were rinsed, and were then reacted with a-HBs-LPS. Then, LPS activity specifically bound to the beads was measured. HBs could be measured in the range of 10(-10)-10(-12) g/mL.

Hepatitis B Antibodies↗
PubMed1991

A quartz crystal viscosity sensor for monitoring coagulation reaction and its application to a multichannel coagulation detector.

A quartz crystal viscosity sensor was applied to a coagulation reaction monitoring system. The system consists of 16 oscillating circuits, a channel selector, a frequency counter, a temperature controller and a microcomputer. The system is named the Quartz Chemical Analyzer (QCA). AT-cut quartz crystals (9 MHz) were used as viscosity detectors and were attached to a cell in order to expose only one side of the quartz plate. The system was applied to the detection of the blood coagulation factors VIII (F VIII) and IX (F IX). The activity of these factors was assayed by a single-stage method. A linear relationship was obtained in a double-logarithmic diagram of concentration versus coagulation time with respect to F VIII and F IX in the range 0.05-0.4 unit cm-3 and 0.025-0.2 unit cm-3, respectively.

Biosensing Techniques↗
PubMed1991

Fluorescence polarization immunoassay employing immobilized antibody.

The use of an antibody immobilized on latex or silver colloid in fluorescence polarization immunoassay (FPI) is assessed. In FPI it is possible to detect antigens of high molecular weight because the molecular weight of the antibody is effectively increased. In the assay for rabbit immunoglobulin G a limit of detection lower by two orders of magnitude and an assay range wider by one order of magnitude can be obtained in comparison with conventional FPI. The detection limit is 10(-10) mol l-1 and the total assay time for one sample is 8 min. This assay combines a low detection limit with a short assay time.

Animals↗
PubMed1991

Development of acetylcholine sensor using carbon fiber (amperometric determination).

An enzyme sensor is developed using carbon fiber to measure acetylcholine concentration. The mechanism is based on the detection of H2O2 which is a product of the sequential enzyme reactions of acetylcholinesterase and choline oxidase. The fabrication of the electrode is described. The sensor is polarized at 1.2 V. Enzymes are co-immobilized in polyvinyl alcohol containing styryl pyrydinium (photo-crosslinkable polymer). A fast response time of 0.8 min is obtained. A linear correlation is observed between 0.2 and 1.0 mM. Other optimal operational conditions with respect to pH, temperature and stability are discussed. The use of carbon fiber containing co-immobilized enzymes could offer several novel advantages especially in neuroscience research. In conclusion, the aims of the present work are centered on carbon fiber electrode fabrication, immobilization and electrochemical measurements.

Acetylcholine↗
PubMed1991

[Biosensors and clinical analysis].

The determination of organic compounds in blood is important in clinical analysis. Most analysis of organic compounds are based on spectrometric methods. However, these methods involve complicated procedures and require a long time for the reaction to occur. Bioelectrochemical sensors employing immobilized biocatalysts have definite advantages. For medical purposes, miniaturization of enzyme sensors is essential. Miniaturized and highly selective enzyme sensors have been developed by combining enzyme immobilization techniques with silicon technologies. Glucose measurement in blood is the most important and essential assay in the clinical field. For this purpose, we have developed various micro biosensors for glucose measurements. Generally, enzymatic determination of glucose is based on the following reaction (s); (formula; see text) According to the above equation, 4 different micro-glucose sensors were developed; 1) a sensor based on the measurement of produced hydrogen peroxide, 2) a sensor based on the measurement of consumed oxygen, 3) a sensor based on the measurement of enthalpy change during the enzymatic reaction, 4) a sensor based on the measurement of the amount of proton produced, and 5) a sensor based on the measurement of the light emission during enzymatic reaction. For these purposes, various kinds of transducers were used. A micro-hydrogen peroxide electrode, a micro-oxygen electrode, a thermistor, an ISFET (ion selective field effect transistor), and a photon counter. The determination of antibodies, or antigens is also very important in clinical analysis. Several types of immuno-sensors have been developed for these purposes. Considering the integration of immuno-sensors, the miniaturization of immuno-sensors is also required. This review deals with our current study on micro-biosensors for clinical analysis.

Biosensing Techniques↗
PubMed1990

Identification of proteins encoded in Escherichia coli hydA, hydB and analysis of the hydA locus.

The hydB gene of Escherichia coli, which is related with the expression of hydrogenase activity, was cloned into the plasmid (pES1). Using the maxicell protein-labeling method, the molecular weight of hydB gene product was estimated. Comparing between the gene products from the mutant strains and that of the hydB genes cloned strains, the molecular weight of the gene product was 35,000 Mr. Similarly, the molecular weight of the gene product of hydA, which had been previously cloned, was determined by maxicell analysis. The molecular weight of hydA gene product was estimated to be 80,000 Mr. Using deletion analysis and Tn1000 insertional inactivation of hydA's function, the hydA coding region was estimated between 2.2 kb and 2.8 kb in a 3.1 kb EcoRI-MluI fragment on the recombinant plasmid pEH3.

Bacterial Proteins↗
PubMed1990

Facile isolation of endo-pectate lyase from Erwinia carotovora based on electrostatic interaction.

Endo-pectate lyase (PATE) from Erwinia carotovora was selectively cosedimented with extracellularly produced lipopolysaccharide-lipid complex (LPSLC) through dialysis of the cell free culture broth. The selective isolation of PATE was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The cosedimentation of the PATE with LPSLC was initiated by decreasing conductivity of the solution and terminated at approx 1 m siemens (mScm-1). As much as 62% of PATE activity in the culture broth was removed by precipitation. PATE was isolated from the precipitate by gel chromatography. The cosedimentation of PATE with LPSLC was remarkably affected by pH or ionic strength. The addition of polycationic peptide polymyxin B sulfate or a metal chloride affected the interaction. The cosedimentation was diminished by acetylation of the free amino groups of PATE. From these results, it was confirmed that the cosedimentation was induced by electrostatic interaction.

Acetylation↗
PubMed1990

Microbial sensor.

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Acetates↗