Improvement of the detection limit of surface plasmon resonance (SPR) apparatus is an important issue when it is applied to immunosensor to detect the biological substances in serum and/or urine. In this study, we investigated two kinds of molecular accumulation methods. The method of consecutive accumulation, in which the second and third antibodies were successively bound onto the antigen (gp41 of human immunodeficiency virus-1), enhanced the SPR response to the anti gp41 antibody binding by about 7 fold. On the other hand, the method of complexed antibody accumulation, in which the second and third antibodies were simultaneously bound onto the antigen, gave the higher response by over 10 fold. In these methods, the appropriate second and third antibodies must be chosen in addition to determination of the preferable concentration.

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Amino acids with different functional group show different taste such as bitterness, sweetness and umami. Some of them elicit complicated mixed taste; e. g., L-methionine tastes bitter and sweet simultaneously. A multichannel taste sensor using lipid membranes was applied to amino acids. It was shown that bitter amino acids such as L-tryptophan have response electric patterns similar to a typical bitter substance, quinine, that belongs to alkaloids. The response pattern for L-methionine was found to be similar to that for a mixed solution composed of a sweet amino acid (L-alanine) and bitter amino acid (L-tryptophan). These results agreed quantitatively with human sensory evaluations.

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Houses are gradually becoming airtight due to heat insulating structures. Thus, air exchange is decreasing in an indoor environment. Indoor air-quality is also worsening by generation of VOCs (Volatile Organic Compounds) from building materials, and it causes sick-house syndrome. On the other hand, it is known that plants and microorganisms inhabiting the rhizosphere purifies indoor air-pollutants. The empirical model, however, involves some problems such as the long interval needed for the measuring of the purification process, and the process is modeled by a simple straight line approximation. In this paper, we find the purification process of plants in detail for the basic study of a design that suitably arranges plants in a room. As an example of a typical foliage plant, a purification process of Epipremnum aureum for formaldehyde is measured continuously using a tin oxide gas sensor. As a result, it is found that the purification rate is fixed at about 40%/h when the formaldehyde concentration range is less than 50ppm in the experimental chamber. Therefore, the purification process could be approximated using an exponential function. Furthermore, the purification rate rose with the increasing intensity of illumination.

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A carbon fiber fabric was modified by oxygen plasma treatment and glucose oxidase(GOD) was covalently immobilized on the modified carbon fiber by use of a condensing reagent. Specific activity of GOD immobilized on carbon fiber fabric was 51 U/mg at 30°C, pH 7. By using the GOD-immobilized carbon fiber fabric as a sensor, amperometric response to glucose was measured at a constant potential of +0.35V vs S. C. E under various pH and temperature conditions. Response current to glucose concentration was found to increase linearly with a slope of 1.8μA per 1mM glucose up to 70mM. The pH and temperature profiles of amperometric response of the GOD-immobilized carbon fiber fabric were similar to those of the activity of GOD.

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Electrical potential oscillation across an octanol membrane consisting of octanol solution containing 5mM tetrabutylammonium chloride between aqueous solution of 1% ethanol and aqueous solution of 8mM sodium dodecyl sulfate and 5M ethanol was measured in the presence of antibiotics. Comparison was made of the mode of potential oscillation in response to antibiotic aqueous solution taste. Four antibiotics, erythromycin, chloramphenicol, ampicillin and cefpodoxime proxetil served as the antibiotics. All antibiotics caused the lower potential of the first pulse, E_L, to shift to more positive values with increase in concentration. Potential immediately after solution contact, E_{_??_}, and potential prior to the start of oscillation, E_H, showed virtually no dependence on concentration. The bitterness of aqueous solution antibiotics was assessed by 8 volunteers (males and females, aged 21-25). For the same antibiotic, E_L increased with bitterness scores. Potential oscillation would thus appear to depend on the degree of bitterness of the same antibiotic. Change in the mode of oscillation according to cefpodoxime proxetil and simple syrup (2.5M sucrose solution, as flavoring agent prescribed by the Japanese Pharmacopoeia) was examined. The oscillation mode for cefpodoxime proxetil corresponded to that due to bitter substances, as previously noted, and cefpodoxime proxetil with 10% simple syrup, sweet substances. The oscillation may reflect the taste of an antibiotic solution, which may be assessed using the octanol membrane.

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Mycelium of Aspergillus niger was cultured aerobically in a liquid medium and immobilized on a carbon electrode. The electrode with immobilized Aspergillus niger was immersed in a buffer solution at pH 6.0 and the current at 0.5 V was measured. The electrode produced an anodic current with the addition of p-benzoquinone as an electron transfer mediator and attained a steady-state. When glucose was added to the solution containing p-benzoquinone, the current increased further and attained a steady-state. The steady-state current with glucose increased with increasing concentrations of glucose. Thus, Aspergillus niger immobilized on the electrode work as biocatalysts in the electrolytic oxidation of glucose. Characteristics and applications of the electrode were investigated.

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An amperometric glucose-sensing electrode was prepared by immobilizing glucose oxidase (GOx) on a polyion complex-modified glassy carbon (GC) electrode. First, a GC electrode was anodized in a 1, 5-pentanediol solution to introduce carboxyl groups on the electrode surface. Next, aqueous solutions of poly-L-lysine and poly (4-styrenesulfonate) were successively placed on the electrode and allowed to dry. Finally a GOx layer was formed on the poly-L-lysine/poly(4-styrenesulfonate)-complex layer by crosslinking the enzyme by the addition of glutaraldehyde. The use of the thin bilayer system with inner, polyion complex membrane, which showed permselectivity based on the solute size with molecular cut-off of ca. 100, brought about high performance characteristics, such as rapid response and low interference level, to the glucose-sensing electrode. The enzyme electrode was useful for the measurement of glucose in beverages involving vitamin C-enriched drinks.

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An amperometric glucose sensor based on carbon paste electrode containing glucose oxidase, nickelocene, and platinum particles was fabricated and characterized. The sensor was functional at a less extreme potential (-200 mV vs. Ag/AgCl) than those of amperometric mediator free sensors. The sensor worked not only in buffer solution but in serum. The output current was unaffected by ascorbate, whose concentration was about two orders of magnitude above the standard ascorbate concentration in human blood. Although the sensor response decreased gradually when native-enzyme was coblended, the sensor in which the enzyme was modified with methoxy-polyethylene-glycol-epoxy was much stabler due to the suppression of enzyme leakage than that with native-enzyme coblended.

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When ac voltage is applied to cell suspensions, response waves analyzed using FFT show the appearance of third harmonics for resting cells and fourth harmonics for active cells. For studying the relationship between electrodes and cells, we examined the appearance of harmonics patterns in electrodes of different materials. The results showed that there were different harmonics patterns between electrode materials. We regard that such particular harmonics patterns derive from the correlation between electrodes and cells.

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Oxygen electrode-based flow-type amperometric mutant sensor was proposed using DNA-immobilized carbon felt as a sensing element for DNA-binding drugs. Catalytic activity of immobilized DNA-Cu (II) complex for air oxidation of aminoethanthiol (AET) was reversibly inhibited by intercalation with DNA binding drugs and antibiotics. Kinetic measurements indicate that quinacrine (QN) competitively inhibits the DNA-Cu (II) complex-catalyzed oxidation of AET. These phenomena could be utilized for development of novel flow-type biosensing system for DNA-binding drugs consisting with immobilized DNA-Cu (II) reactor and oxygen electrode detector. The peak-shape current responses were observed for various DNA-binding drugs, and the magnitude and the shape of the responses depend considerably on the kinds and concentrations of DNA-binding drugs.

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Lactose sensors were fabricated by an avidin/biotin method. Biotinylated glucose oxidase (GOx) and β-galactosidase (β-Gal) formed bienzyme membrane on a Pt electrode by a layer-by-layer deposition of avidin and the biotinylated enzymes. The modified electrode functioned satisfactorily as a lactose sensor, in which two enzymatic reactions were coupled. Ten layers of GOx were deposited on the electrode, and then β-Gal layers were deposited step by step on the GOx layer. The response current of the sensor to lactose increased with increasing the number of depositions of β-Gal; I_max values were 8.4 nA for 2 layers, and 81.3 nA for 12 layer of β-Gal.
Three types of arrangement of the enzymes in the membrane were prepared; (5x GOx)+(5x β-Gal), (5x β-Gal)+(5x GOx) and 5x (GOx+β-Gal). The sensor modified with the alternate layers of GOx and β-Gal, 5x (GOx+β-Gal), exhibited a highest signal for lactose. The avidin/biotin method was shown to be useful to optimize composition of the bienzyme membrane.

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Highly sensitive detection of methamphetamine (MA) was realized by using an immunosensor based on surface plasmon resonance (SPR) phenomena. A methamphetamine-bovine serum albumin (MA-BSA) conjugate was prepared as an antigen, and it was immobilized on the Au thin film of sensor-chip. Introduction of MA into the antibody solution was found to decrease the incident angle shift sharply because of the inhibition effect of MA. Association constants between anti-MA antibody and MA as well as anti-MA antibody and MA-BSA were evaluated from the Langmuir isotherm adsorption model. The association constants between anti-MA antibody and MA or MA-BSA were estimated as 5.68×10⁶M^-1, 2.92×10⁷ M^-1 respectively. The association rate constant and dissociation rate constant were also estimated from typical transient responses to antibody solutions.

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This paper describes an application of taste sensor for detection of cyanide. The taste sensor consists of multichannel sensors with lipid membranes which are modeled on living organisms. One of characteristics of this sensor is a global selectivity. In this study, we have developed a new effective method which is able to control the charge of membranes for high sensitivity and selectivity of lipid membrane sensors. Using this method, sensors for free cyanide and complex cyanide were developed. We could detect total cyanide under the guideline limit. It was possible to detect free cyanide below the concentration 0.5ppm in river water. Measurement time is within five minutes. In conclusion, the taste sensor has a very powerful performance and advantage for real time monitoring of water quality.

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The oxidase-peroxidase (HRP) co-immobilized electrode was characterized from the standpoint of an integrated miniature enzyme electrode development for diagnostic applications. The sensor characteristics were examined in terms of (1) contribution of enzyme immobilization materials, (2) use of other oxidases than glucose oxidase (GOD), and (3) control of enzyme sensor responses by controlling an electro-conductivity of an enzyme immobilized membrane. By comparing responses of GOD-HRP electrodes prepared by a polypyrrole, a polyphenylenediamine, a glutaraldehyde-crosslinking or a photocrosslinking polymer PVA-SbQ, it was shown that the electro-conductivity is necessary for enzyme immobilization materials of the oxidase-HRP electrodes. When lactate oxidase or glutamate oxidase was immobilized with HRP in a polypyrrole, cathodic current similar to the GOD-HRP electrode was observed. Finally, by using a polyaniline membrane, the sensor response of the GOD-HRP electrode could be controlled by successive reduction and oxidation of a polyaniline membrane.

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In micro mechanical devices with high aspect ratios, LIGA or LIGA-like processes are commonly used. In such a process, the material of the device structure is electroplated with nickel or copper because of ease of deposition. In this paper, an alternative material, electroplated nickel-tungsten alloy is examined as an MEMS material. Preliminary results of measurements of the mechanical, chemical and magnetoelectrical properties are shown and discussed. It is found that the Ni-W alloy film shows excellent characteristics such as low internal friction, high chemical resistance.

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The photodiodes with a vertical overflow drain are generally used in CCD image sensors. During the charge storage time, the minimum potential point in the barrier region moves toward the photo-diode surface. Almost incident light of short wavelength is absorbed within the surface side shallower than the minimum potential point. Therefore, nonlinearity between the incident light intensity and the output signal does not occur. However, for long wavelength light, since considerable light absorption takes place around the minimum potential point, the nonlinearity arises. The measured nonlinearity for the red incident light was about 5%. The nonlinearity obtained by the calculation coincided qualitatively with that of the measurements. Also, the calculation made clear that the wider barrier width, the low barrier impurity concentration, the low substrate impurity concentration, narrow storage region width, and low substrate bias enhance the nonlinearity.

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