学術雑誌リスト

Electrochemical oxidation of glucose in alkaline solution at as-prepared boron-doped microcrystalline diamond (BDMD) and nanocrystalline diamond (BDND) thin-film electrodes is investigated by cyclic voltammetry. The results demonstrate that glucose can be directly oxidized at as-prepared boron-doped diamond (BDD) thin-film electrodes and the curve of the negative scan traces onto the positive scan. The effect of sodium hydroxide concentration on the response of glucose is also studied in the range of 0.02–0.6 M and the optimum concentration of sodium hydroxide is found to be 0.1 M. The voltammetric signal of glucose and the mixture of ascorbic acid (AA) and uric acid (UA) can be observed well-separated at as-prepared BDD thin-film electrodes in 0.1 M sodium hydroxide solution. The peak current is proportional to the glucose concentration in the range 0.25–10 mM with a correlation coefficient of 0.9993 in the presence of AA and UA. Furthermore, the experiment results also show that the non-enzymatic glucose sensor based on as-prepared BDD thin-film electrodes has high sensitivity, good reproducibility and stability.

In this article, we show that the optical texture of a layer of liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) supported on a thiol-sensitive layer can be applied to detect 1-octanethiol and other vaporous thiols with high specificity. As demonstrated in our ellipsometry and XPS results, a thiol-sensitive layer comprising an array of copper ions is capable of oxidizing thiols to disulfides and immobilizing them on the surface. Because of the hydrophobic hydrocarbon chain of 1-octanethiol, the immobilization of 1-octanethiol lowers the surface energy. Thus, after a thin layer of 5CB is supported on the surface, the lower surface energy causes 5CB to adopt different orientations in regions where copper ions were deposited. Because 5CB is a birefringent material, different orientations of 5CB also result in distinct optical textures, which are visible to the naked eye under a pair of polarizers. Interestingly, 5CB supported on copper ions only responds to longer and less volatile thiols such as 1-octanethiol, 1-hexanethiol and 1-butanethiol, but it did not respond to shorter and more volatile thiols such as ethanethiol. The system also shows no response to water and other volatile organic compounds such as acetone, ethanol, heptanol and heptane.

Oxygen is a major actor of many physiological, biological and industrial processes; as such, its monitoring is of paramount importance. The effects of protein biofouling on dissolved oxygen measurements are described. The consequences of protein adsorption on electrode kinetics and mass transport were quantified using cyclic voltammetry, AC impedance and rotating disc amperometry, firstly in a solution of albumin, secondly in a complex protein suspension of liver tissue. The effect of membrane coatings poly(styrene-sulfonate)/poly(L-lysine) and fibronectin were investigated. The relative significance on mass transport, surface diffusion and electrocatalysis were examined by comparing the experimental data for an outer-sphere redox couple, ruthenium hexaammine (III)/(II), with the physiologically significant electrocatalytic O2reduction reaction.

Liposome-based nanoSized Particles with Incorporated Nitroxides, or nanoSPINs, were designed for EPR applications as pH probes in biological systems. Phospholipid membrane of the liposomes with incorporated gramicidin A showed selective permeability to a small analyte, H+, while protecting entrapped sensing nitroxide from biological reductants. An application of the pH-sensitive nanoSPIN in an ischemia model in rat heart homogenate allows for monitoring ischemia-induced acidosis while protecting encapsulated nitroxide against bioreduction.

We have investigated the effectiveness of surface-adsorbed silver half-shells for inducing the surface-enhanced fluorescence phenomenon. Our simple structure consists of a dense monolayer of monodispersive latex sphere covered by thermally evaporated silver, some tens of nm thick. In order to increase its effectiveness as a platform for immunoassay, we explored three physical parameters; the diameter of the latex sphere, the deposition thickness and the adsorption density of the latex sphere. The maximum enhancement of 25.5 was achieved using the sphere with 56 nm diameter with 10 nm silver deposited. As for the adsorption density, the maximum fluorescence signal was achieved with a relatively sparse adsorption density, 12.5 per µm2vs. 105.9 per µm2, corresponding to the full coverage. With the adsorption density also optimized, the enhancement was further increased by a factor of three.

Selective removal of hexavalent chromium ions from aqueous solutions using a chitosan/gold nanoparticles composite film was demonstrated. Localized surface plasmon resonance (LSPR) was used to measure the interface stability and detect the incorporation of chromium ions over time. The effects of pH, ethylenediaminetetraacetic acid (EDTA), and various foreign ions such as trivalent chromium, sodium, calcium, phosphate, sulfate and chloride on the adsorption of hexavalent chromium were investigated.

An electrochemiluminescence (ECL) detection system equipped with an electrically heated indium-tin-oxide (ITO) electrode was constructed. The heated ITO electrode (HITOE) coupled the advantages of a heated electrode with the optical transparency property of ITO glass. Compared with the conventional heated electrode, the HITOE is integrated into the ECL cell, which could save the expensive luminescent reagent. The temperature of the electrode (Te) could be accurately controlled by electrically heating. The Ru(bpy)32+/TPrA ECL system and the colchicine/Ru(bpy)32+ ECL system were used to evaluate the developed ECL detection system. The higher sensitivity and lower RSD of ECL detection for tri-n-propylamine (TPrA) and colchicine were gained by moderately heating the electrode. The proposed method has been successfully utilized to the assay of colchicine in a spiked human serum sample. The results indicated that the developed ECL detection system could provide high sensitivity and excellent reproducibility for analytical practice.

Desorption electrospray ionization mass spectrometry (DESI-MS) of culture of the bacterium Bacillus subtilis as a biofilm growing on agar nutrient gives simple, high quality mass spectra dominated in both the positive and negative ion modes by signals due to the cyclic lipopeptide, Surfactin(C15). This in vivo experiment, performed by direct analysis of untreated microorganism samples under ambient conditions, allows rapid identification of this microorganism and the antibiotics that it produces. The result is suggestive of the capabilities of DESI-MS for in vivo microorganism characterization in general and for monitoring fermentation processes for the production of antibiotics and other biochemicals.

In recent years, biotechnologically-derived drugs have been a major focus of research and development in the pharmaceutical industry. Their pharmacokinetics and pharmacokinetic/pharmacodynamic relationships impact every stage of the development process and require their assessment in the circulation in preclinical species and in humans. To this end, immunoassays are a reference, but standardisation remains an issue owing to the restricted pattern of antibody specificity and interference with endogenous components. As an alternative, we report here analytical strategies involving liquid chromatography coupled to mass spectrometry (LC-MS) for the accurate quantification of therapeutic proteins and antibodies in biological fluids.

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