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Fabrication of nanoparticles by electric discharge plasma in liquid

Yatsu S, Takahashi H., Sasaki H., Sakaguchi N, Ohkubo K, Muramoto T., Watanabe S.

Archives of Metallurgy and Materials

2013

Vol. 58, iss. 2

425--429

The electric plasma discharge method involves the application of a voltage between a cathode and anode in a conductive electrolytic solution to create a discharge plasma at the cathode. When certain material is used as the cathode, small droplets are emitted with the plasma discharge, and the melted droplets are rapidly cooled in the solution to form nanoscale particles of the material. In this work, nanoparticles of Al, Au, Si, and various alloys of between 100 nm and less than 10 nm in size were produced and characterized. Characterization of Si nanoparticles is especially important because their use in lithium batteries greatly influences battery performance. It was found by high resolution electron microscopy and microstructural surface analysis that oxidation layers of a few nm in thickness were formed on the surface of the Si nanoparticles.

W metodzie wyładowań elektrycznych w cieczy pod wpływem przyłożonej różnicy potencjałów pomiędzy anodą i katodą zanurzonymi w elektrolicie dochodzi do wyładowania plazmy na katodzie. Gdy zastosuje się materiał jako katodę, podczas wyładowania plazmy tworzą się małe krople ciekłego materiału, które gwałtownie krzepną w elektrolicie. W ten sposób wytwarzane są cząstki nanometrycznej wielkości. Przy użyciu tej metody możliwe jest wytwarzanie nanocząstek różnych materiałów. Wytworzone nanometryczne cząstki Al, Au, Si oraz stopów miały wymiary od 100 nm do poniżej 10 nm. W szczególności nanocząstki Si stosowane do wytwarzania baterii litowych znacząco wpływają na wydajność baterii, z tego tez powodu bardzo ważne jest scharakteryzowanie tych cząstek. Obserwacje przy użyciu wysokorozdzielczej transmisyjnej mikroskopii elektronowej i analiza mikrostruktury nanocząstek Si wskazują, że na powierzchni cząstek znajduje się warstwa tlenków o grubości kilku nm.

Determination of optimal cyclic uniaxial stretches for stem cell-to-tenocyte differentiation under a wide range of mechanical stretch conditions by evaluating gene expression and protein synthesis levels

Morita Y., Watanabe S., Ju Y., Xu B.

Acta of Bioengineering and Biomechanics

2013

Vol. 15, no. 3

71--79

We examined optimal cyclic uniaxial stretches for stem cell-to-tenocyte differentiation by applying a wide range of cyclic mechanical stimuli. Human bone marrow mesenchymal stem cells (hBMSCs) were subjected to three types of cyclic elongation of 5%, 10%, or 15% at a cyclic frequency of 1 Hz for 24 h or 48 h, and differentiation into tenocytes was assessed by two methods: real-time polymerase chain reaction determination of gene expression levels and western blotting analysis of protein expression levels. The gene expression levels of the differentiation markers type I collagen (Col I), type III collagen (Col III), tenascin-C (Tnc), and scleraxis (Scx), all of which are constituents of tendon tissue, were increased when cells were exposed to 10% stretching stimulation. The levels of Col I and Tnc protein synthesis levels were also higher in the cells with 10% stretching stimulation than in those subjected to other stimuli. The results indicated that 10% stretching stimulus was efficient to induce the differentiation of hBMSCs into tenocytes. In addition, the changes in gene and protein expression levels were strongly correlated with cell orientation angle. The results presented here suggest that mesenchymal stem cell-to-tenocyte differentiation is strongly associated with cumulative elongation load on the cells. This work provides novel insights into the differentiation of tenogenesis in a strain-induced environment and supports the therapeutic potential of hBMSCs.

Separation and estimation of bisphenol a by liquid chromatography with UV detection

Nagahashi M., Kikuchi N., Migaki E., Watanabe S., Miki T.

Acta Chromatographica

2000

No. 10

110-122

Reliable HPLC separation and estimation of bisphenol A has been performed on a conventional ODS column with 40:60 acetonitrile–water as mobile phase and UV detection at 277 nm. Linear regression plots were obtained for the dependence of response on bisphenol A concentration in the working ranges 2 to 10 ng and 10 to 100 ng; the correlation coefficients for the plots were r = 0.9976 (n = 5) and r = 0.9987 (n = 6), respectively. Aqueous samples were applied to a solid-phase extraction cartridge packed with three layers, Bio-Rad AG 50W X8 [H+], ODS–silica, and Bio-Rad AG 1 X8 [formate–]. Eluent from this cartridge was passed through a normal-phase Florisil PR cartridge. These isolation and purification cartridges effectively separated and purified bisphenol A from spiked samples with recovery between 86 and 92%. The method was used to estimate bisphenol A in water samples.