Rapid determination of nicotinic acid by immobilized lactobacillus arabinosus

A rapid determination of aicotinic acid by using immobilized Lactobacillus arabinosus and a combined glass electrode is reported. L. arabinosus is immobilized in agar gel. The optimum agar concentration is from 2–2.5% ($\text{w}\text{v}$) and the optimum bacterial concentration in the agar gel matrix is 10 mg wet cells ml^-1. The relationship between the potential difference and the logarithm of the nicotinic acid concentration is linear over the range 5 X 10^-8–5 X 10^-6 g ml^-1. The assay requires only 1 h; potentials are reproducible with an average relative error of 5%. The growth of L. arabinosus in agar gel matrix is observed in the medium containing nicotinic acid. Immobilized L. arabinosus is stable for 30 days.     

Photocontrolled binding of cytochrome C to immobilized spiropyran

Agarose gel was modified with polyethyleneimine and β-l-[3,3-dimethyl-6’-nitrospiro-(indoline-2,2’-2H-benzopyran)] propionic anhydride and the binding of cytochrome c was investigated. Cytochrome c was not retained on agarose modified only with polyethyleneimine. However, cytochrome c interacted with the immobilized spiropyran during illumination, but 0only a relatively small amount was bound to the immobilized spiropyran in the dark. The maximum difference of cytochrome c binding was observed at pH 6.8. Forty-six percent of cytochrome c bound on immobilized spiropyran in the column under visible light was released from the gel in the dark. This released cytochrome c showed the same spectrum and properties as those of native cytochrome c.     

Continuous neutral lipid determination with lipase-collagen membrane reactor

Lipase (Pseudomonas sp.) was immobilized in collagen membrane and used for the measurement of neutral lipids. The determination system for lipids consisted of a lipase-collagen membrane reactor and glass electrodes. Neutral lipids were hydrolyzed to fatty acids and glycerol by immobilized lipase. The liberated protons were determined potentiometrically by using glass electrodes. A linear relationship was obtained between the logarithm of lipid concentrations and potential differences. The measurement gave results comparable to a conventional assay and was found to be applicable to the assay of neutral lipids in sera. The relative error of the determination by this system was within 4%.     

Flow injection microbial trichloroethylene sensor

A flow type microbial biosensor for direct measurement of trichloroethylene (TCE) was developed. The unique features of this novel microbial sensor were the use of the TCE degrading bacterium Pseudomonas aeruginosa JI104, the electrical detection of the chloride ion released by microbial degradation, and flow cell made of glass. Glass cell was used in order to suppress adsorption of TCE and made a closed reaction cell. Vaporization of TCE during the measurement was prevented using closed flow cell. The performance of the sensor was evaluated from following aspects; such as pH of the carrier solution, amount of the immobilized microbe, flow rate and injection volume. The sensor signals were linearly proportional to the concentration of TCE in the range from 0.03 to 2 mgl(-1), which is suitable for the determination of suspected samples to be drinkable water or not. The sensor performance was checked on the real sample, and this system showed good response in ground water, indicating its applicability for the on line monitoring at TCE contaminated areas or hazardous sites.     

A simple and highly repeatable colorimetric toxicity assay method using 2,6-dichlorophenolindophenol as the redox color indicator and whole eukaryote cells

A simple and highly reproducible toxicity assay method was studied by employing 2,6-dichlorophenolindophenol (DCIP) as a redox color indicator, baker’s yeast Saccharomyces cerevisiae, and a thermostable three-consecutive-stir unit. The absorbance of DCIP was decreased by increasing the metabolism activity of S. cerevisiae to intake glucose as an organic substance. By optimizing the measurement conditions, we obtained highly sensitive responses to glucose between 0.75 and 30 mg/L (eight points, n = 3) with an incubation time of the reaction mixture of 10 min at 30 °C. An excellent value of 1.15% was obtained as the average of the repeatability from eight points. Next, for the characterization of this method, we investigated the influence on the colorimetric response of dissolved substances, such as inorganic ions and surfactants, in natural water. Furthermore, the colorimetric responses to several toxicants were examined using Cu²⁺, Mn²⁺, Zn²⁺, Cr³⁺, and Fe³⁺ as heavy-metal ions and simazine as an agricultural chemical. As a result, notable colorimetric responses were obtained for Cu²⁺ and Mn²⁺ at several concentrations, and the results were compared with those obtained using river water as a real sample. In the stability test, responses to 30 mg/L glucose were obtained for 28 days when the yeast cell suspension was stored at 4 °C (response reduction, 43.9%; average of the relative standard deviation for nine testing days, 22.7%; average of repeatability, 1.01%). Figure Graphical image of the colorimetric toxicity assay     

Simultaneous iso-electric focusing of proteins in a micro-fabricated capillary coated with hydrophobic and hydrophilic plasma polymerized films

The ability to modify and reduce the electroosmotic flow (EOF) is one of the most influential parameters which affects iso-electric focusing (IEF) of proteins. Therefore capillaries are usually coated with polymers or gels to prevent non-specific adsorption and suppress the EOF in capillary iso-electric focusing (cIEF) of proteins. In this research hexamethyldisiloxane (HMDS) and 2,3-epoxy-1-propanol (glycidol) plasma polymerized films were deposited onto both surfaces of the capillary separation channel. Cathode solution pH 3, anode solution pH 10 and a carrier ampholyte, pharmalyte provided the necessary stable pH gradient. Simultaneous IEF of proteins in capillaries coated with hydrophobic and hydrophilic plasma polymerized films occurred within minutes. The electroosmotic force of uncoated glass capillaries was suppressed by 50% after deposition of 200 nm 2,3-epoxy-1-propanol compared with a 30% reduction of EOF when the capillary was coated with 200 nm HMDS. The hydrophilic 2,3-epoxy-1-propanol plasma polymerized film was more resistant with a stronger attachment to the glass surface than previously prepared acetonitrile plasma polymerized films.     

Selective piezoelectric odor sensors using molecularly imprinted polymers

Molecular imprinting technique has been used to create sensors with a predetermined selectivity for molecules in the gas phase. Piezoelectric quartz crystals coated with a 2-methylisoborneol (MIB) imprinted polymer gave responses which were consistently 5–10 Hz (1.1–1.3 times) higher than those of sensors coated with a non-imprinted polymer. Geosmin, another tertiary alcohol odorant with an earthy odor resembling, and often accompanying MIB, produced almost equal responses on either imprinted- or non-imprinted sensors. A number of other odorants were examined and their responses to the non-imprinted sensors were found to be similar to or greater than their responses to the imprinted sensors. The responses of MIB to the imprinted sensors were always the highest, while other odorants produced equal or higher responses using the non-imprinted sensor. The sensor has a detection limit of ca. 5 mg l⁻¹ and a dynamic range of at least 1000 mg l^−l. When the time taken for the sensor to stabilize is used as the response, instead of the frequency change, the detection limit is lowered to ca. 200 μg l^−l.     

Effects of GaAs and Ga2O3 on magnetometric behavior of iron oxide particles in rabbit lungs

Intratracheal instillation of a GaAs suspension has been histopathologically shown to induce a diffuse pulmonary response. In the present study, magnetometry was used to evaluate the effects of intratracheally instilled GaAs and Ga₂O₃ on the behavior of externally magnetized iron oxide (Fe₃O₄) particles instilled in rabbit lung. Magnetometric evaluation of the effects of GaAs in rabbits dosed with 30 mg or 300 mg per animal showed a significantly decreased relaxation of iron oxide particles at 1, 3, 7, 14, 21 and 28 days following instillation compared with the controls. On the other hand, in the rabbits exposed to Ga₂O₃, significantly reduced decay constants were observed only on the first and third days following instillation. Relaxation indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytosed iron oxide particles in macrophages. Clearance of the iron oxide particles was measured by serial determinations of the remanent magnetic field at the end of magnetization estimated from relaxation curves. Clearance was significantly impaired at 14, 21 and 28 days after instillation in rabbits exposed to both doses of GaAs. Slightly delayed clearance was also observed in rabbits exposed to Ga₂O₃. Histological examination of lungs instilled with GaAs indicated active phagocytosis of GaAs and iron oxide particles by pulmonary macrophages, as well as pneumonocytes hyperplasia with marked thickening of the alveolar walls. Minimal histological changes with retention of iron oxide particles were found in the lungs exposed to Ga₂O₃.