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Biomedical subjects

I Karube

Publications and source records attributed to I Karube.

At least 73 records · Page 4Linked to original sources
PubMed1995

Development of a thin membrane glucose sensor using beta-type crystalline chitin for implantable biosensor.

A biocompatible thin membrane glucose sensor has been developed using beta-type crystalline chitin as a supporting material for the purpose of implantable biosensor. Gold electrode was formed by vapor deposition of the surface of glucose oxidase-immobilized beta-chitin membrane. The sensor showed rapid responses to glucose and H2O2 (< 45 s in batch operation), and addition of 2,6-dichlorophenolindophenol as a mediator caused expansion of the measuring range. To investigate the possible uses for the implantable, the sensor sterilization and toxicity were studied. Sterilization with ethylene oxide was achieved by exposing samples, and a decrease in activity was permissible for measurements of body fluid. From the results of the toxicity assay using mouse fibroblast cells, beta-chitin sensor, constructed with chitin, glucose oxidase and gold electrode, showed no particular toxicity.

Animals↗
PubMed1995

A glucose sensor fabricated by the screen printing technique.

A novel glucose sensor employing ferrocene-modified glucose oxidase is fabricated using the screen printing technique. Glucose oxidase is covalently bound to the electron mediator ferrocenecarboxylic acid in order to obtain higher enzyme activity. The ferrocene-glucose oxidase shows an increased catalytic current because the ferrocene acts as an electron transfer relay between the active centre of the enzyme and the gold electrode. Glucose sensors employing enzymes modified with ferrocene in various ways are successfully fabricated using the screen printing technique. The ink component containing the ferrocene-glucose oxidase is specially developed to be applicable to the printing machine. The printed glucose sensor chip offers a stable calibration profile and stable electrochemical properties.

Biosensing Techniques↗
PubMed1995

Measurement of tear electrolyte concentration and turnover rate using a flexible conductimetric sensor.

Tear fluid conductivity was measured by a non-invasive method. A flexible 3 mm-wide conductimetric sensor was placed inside the human subjects temporal lower cul-de-sac (similar to Schirmer test strip), and used to evaluate electrolyte concentration and turnover rate in tear for normal, healthy subjects aged between 30 to 85 years in a normal, light indoor environment. The tear electrolyte concentration was calculated from tear conductivity to give a mean value of 297 mEq/l (S.D. 30 mEq/l; n = 29) which was consistently with previously reported values. Tear turnover rate was calculated by a single exponential equation of tear conductivity change, following the application to the eye-drops of 40.0 milligrams sodium chloride solution. The mean turnover rate was 44.2% per minute (S.D. = 13.3% per minute; n = 30), being in agreement with previously reported values.

Adult↗
PubMed1994

Micromachined electroporation system for transgenic fish.

Luciferase gene was introduced into fertilized eggs of medaka by a localized electric field between thin film electrodes formed on a glass plate. Miniaturization of the electrodes enabled us to apply a localized electric field to the animal pole of the fertilized egg. Biochemical luminescence and an electrophoresis pattern showed expression and integration of the gene, respectively. The presented system had a higher ratio of gene introduction than the conventional electroporation method.

Animals↗
PubMed1994

Multisample analysis using an array of microreactors for an alternating-current field-enhanced latex immunoassay.

To develop a rapid and multisample analysis system for latex immunoassay with submicroliters of sample, an array of microreactors were fabricated using micromachining techniques including photolithography, anisotropic etching, and thin gold film deposition. The chamber volume for immunoreactions of a single well was 0.4 microL. An alternating-current (ac) field was used to enhance the rate of the latex agglutination reaction. By applying an ac field for 1 min, alpha-fetoprotein in several samples could be determined simultaneously. The detection limit in this system was approximately 10 pg/mL.

Female↗
PubMed1994

Influence of cationic antibiotics on phase behavior of rough-form lipopolysaccharide.

The rough-form lipopolysaccharide (LPS) interacted with cationic antibiotic polymyxin B and gramicidin S in solution, and showed altered thermotropic phase behavior and viscoelasticity. The phase behavior was measured by differential scanning calorimetry and quartz crystal microbalance (QCM). Addition of polymyxin B of up to 0.5 mg/mL to the 5.0 mg/mL LPS solution increased gel-to-liquid crystalline phase transition enthalpy (delta H) and raised the transition temperature (tmax). The further addition of polymyxin B reduced the delta H value. Gramicidin S produced a different effect, whereby a minor addition reduced tmax and delta H value of the LPS. The LPS film on the platinum electrode of the QCM indicated a downward shift of resonant frequency and an upward shift of resonant resistance when in contact with the antibiotic solution. An interpretation of these variations is that the LPS on the QCM electrode changed not only film weight, but also viscoelasticity owing to contact with the antibiotic solution. The different effects between the antibiotics between polymyxin B and gramicidin S on the LPS are induced by the difference of the governing effect. Polymyxin B interacts with the LPS electrostatically, whereas gramicidin S interacts by hydrophobic moieties.

Calorimetry, Differential Scanning↗
PubMed1994

Immobilized cells used for detection and analysis.

Many kinds of biosensor have now been developed and utilized for various types of analysis including clinical, medical and environmental monitoring, industrial process control, as well as many other applications. The microbial biosensor has advantages, such as longer lifetime and lower cost, over other types of biosensor. Recently, photobacteria and recombinant bacteria have been employed in biosensors both for determining biochemical oxygen demand and for detecting heavy metals and other toxic compounds.

Biosensing Techniques↗
PubMed1994

Thin film formation by rough form lipopolysaccharide and interaction with cationic antibiotic polymyxin B.

A monolayer film of the rough form of lipopolysaccharide (LPS) from Erwinia carotovora at an air-water interface was transferred onto solid substrates to form a multilayer film. The LPS was deposited on hydrophobic graphite as well as on hydrophilic platinum plates. The thickness of the LPS film prepared by a single dipping and removal of the graphite was estimated at 2.7 nm by atomic force microscopy. The repeated dipping of the platinum plate indicated early saturation with reduced subsequent absorption from the pure water subphase, while successive transfers of the LPS were observed from a 2.0 mM MgCl2 solution. The LPS film on the quartz crystal microbalance (QCM) interacted with cationic antibiotic polymyxin B in the solution and exhibited a downward shift of resonant frequency and resistance in proportion to its concentration. The resonant resistance change against the resonant frequency axis was parallel in this interaction. The absorption of the antibiotic on the LPS film prepared in the presence of MgCl2 indicated an increase in mass, but little change in viscoelasticity. A multilayer film of LPS on the QCM was found suitable for subsequent characterizations.

Absorption↗
PubMed1993

Microbiosensors for acetylcholine and glucose.

Microbiosensors based on carbon and and platinum fibers are described. Carbon fibers were used to construct microelectrodes of 7 microm diameter. Electrochemical operations for pre-electrolysis and measuring were examined for the highly sensitive determination of hydrogen peroxide. A triangular potential (-2 to +2V vs Ag/AgCl) was applied before measuring each pair of double pulses (first pulse: 750 mV; second pulse: 1100 mV). The determination limit was 0.1 microM of hydrogen peroxide. The reproducible determination of hydrogen peroxide is possible even in samples containing albumin protein. The separation of hydrogen peroxide from ascorbic acid is also possible because the oxidation potential of ascorbic acid is different from that of hydrogen peroxide. An acetylcholine microsensor was fabricated by immobilizing acetylcholine esterase and choline oxidase on the carbon fiber by entrapment with poly(vinyl alcohol)-quarternized stilbazole (PVA-SbQ). This sensor gave a linear calibration plot for the range 0.1-1.0 mM with a linear correlation coefficient of 0.9842. Glucose oxidase (GOD) and glucose dehydrogenase (GDH) immobilized cylindrical platinum microelectrodes were fabricated, and their characteristics were evaluated, respectively, by using 1,4-benzoquinone (BQ) and ferricyanide as electron mediators. Each enzyme was immobilized by using PVA-SbQ on a cylindrical microelectrode of 2 microm diameter. A linear range in the calibration curve of the GOD-based glucose microsensor was observed to be wider than that obtained using a disk electrode of 1 mm diameter. The mediated response of the 2 microm glucose sensor was compared with the response resulting from hydrogen peroxide detection. This result showed that a higher response and a wider linear range were observed with highly concentrated mediator. A much higher response of the GDH immobilized 2 microm microelectrode was obtained when not only ferricyanide but also diaphorase was employed to reoxidize the NADH produced by the enzyme reaction of GDH. The GHD-based glucose microsensor was found to be unaffected by the concentration of dissolved oxygen.

Acetylcholine↗
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↗