Papers by Author: Masaru Hakoda

Abstract: In order to clarify the relation between ReKω and the electrical property of each intracellular part, we loaded temperature stress on the cells. In this experiment, the electrical property of the intracellular part means the cytoplasm electrical conductivity (σ₃) and the cell membrane capacitance (C_m). ReKω of the cells was measured using dielectrophoresis (DEP) levitation, and the electrical property of each intracellular part was analyzed from the measurement result in applying a single shell model. In this experiment, mouse hybridoma 3-2H3 cells were used as the sample cells. Temperature stress was loaded on the sample cell at 5% CO₂ in a CO₂ incubator. The result of the frequency characteristic of ReKω using DEP levitation showed that both ReKω and the crossover frequency of the single cell in the high frequency region decreased with increasing temperature. Furthermore, both the cytoplasm electrical conductivity and the cell membrane capacitance decreased with increasing temperature stress.

Abstract: In this study, we analyzed differences in cell species using dielectrophoresis (DEP) and propose a particle packed bed type chromatography device using DEP. Mouse-hybridoma 3-2H3 cells were used as the sample cells. The 3-2H3 cell suspension was fed pulse-wise to a carrier flow and the sample was measured by an absorption spectrometer. The analytical characteristic of chromatography using DEP was evaluated by the retention time difference. We examined the effects of the diameter of packed particles on the retention time difference. The retention time difference in the case of the packed particles of 100 μm diameter was larger than that of 500 μm, which suggests that packed particles of smaller diameter are suitable for analysis using DEP chromatography.

Abstract: This paper reports the separation of cells using a dielectrophoretic (DEP) chromatography device. The device consists of a micro channel and an array of interdigitated microelectrodes on a glass substrate. The sample cells were fed pulse-wise into the carrier flow using a micro-injector. The cells in the sample received a non-uniform electric field made with an electrode array. The direction of DEP motion is towards the higher field when the cell is more polarizable than the medium (positive DEP), while the direction is towards the lower field when the cell is less polarizable than the medium (negative DEP). Therefore, the cell separation depends on the size and dielectric characteristic. The effects of carrier flow rate, frequency, applied voltage, and sweep frequency on the retention time of the sample in the device were examined. In this study, mouse-hybridoma 3-2H3 cells and yeast cells were used as the sample cell. The analytical characteristic of the DEP chromatography device was evaluated according to the difference of retention time by the electric field. As a result, the separation in the cells in the negative DEP using the DEP chromatography was found to be effective. In addition, the effect of the sweep frequency on the difference in the retention time of the mouse hybridoma 3-2H3 cells and the yeast cells was very large. Consequently, the effectiveness of the DEP chromatography device was proven.

Abstract: In our previous study, we discussed the possibility of differentiation activity measurement for rat mesenchymal stem cells (RMSC) by Dielectrophoretic (DEP) levitation. Consequently, it was found that the differentiation activity of the RMSC could be evaluated by DEP levitation without the differentiation induction. Thus, we discuss the possibility of differentiation activity evaluation by DEP levitation with cells other than the RMSC. Human mesenchymal stem cells (HMSC) and human adipose tissue-derived stem cells (ASC) were used as the sample cells. The dielectric characteristics (Re[K(ω)]) measurement, the Re[K(ω)] of both the HMSC and the ASC decreased with the increasing passage number. Moreover, to evaluate the differentiation activity of the HMSC and the ASC that had performed the osteoblast differentiation induction, the amount of Alkaline Phosphatase (ALP) was measured. Consequently, the ALP activity of both the HMSC and ASC decreased with increasing the passage number. Therefore, it was found that the differentiation activity of the HMSC and the ASC could be evaluated by measuring the Re[K(ω)] due to the relationship between the Re[K(ω)] and ALP activity.