Narrow Results

Microfluidic technology has achieved a rapid technological advancement and become well admired in miniaturized laboratory works. Effectiveness of laboratory works such as protein and glucose analysis, and pharmaceutical study depends on convenient sample preparation. These processes involve dilution of the primary reactant with buffer fluid in an appropriate proportion to ensure error-free bioassay operations in the future. In this paper, a decision tree-based method is proposed to construct the mixing tree for exploring all possible combinations of concentration values to generate the target sample for different biochemical experiments. This work is also extended for multi-target sample preparation concurrently to reduce the sample preparation time and cost. The simulated result shows that the proposed technique not only reduces the mixing/dilution operations for single-target sample preparation but also minimizes the use of primary reactant compared to the contemporary approaches and an enhanced outcome is also achieved for multi-target sample production.

Ashes generated in the incinerator for radioactive waste at the Kaya Memorial Takizawa Laboratory was analyzed using the PIXE system established at the Nishina Memorial Cyclotron Center. An easy method of sample preparation of ash powder for the PIXE is described. Many elements in the ash sample were detected. The PIXE used in this study is shown to be a very valuable method for analyzing the ash.

Non-radioactive liquid waste generated in the Kaya Memorial Takizawa Laboratory was analyzed using the PIXE system established at the Nishina Memorial Cyclotron Center. Samples of the liquid waste were collected at several stages of the non-radioactive liquid waste purifying process. A simple sample preparation method for liquid sample was adopted. Liquid sample was dropped and dried directly on the backing film after adding the internal standard element, which produced appropriate targets to be analyzed by PIXE. Sodium, silicon, sulfur, chlorine, potassium, calcium, iron and so on in the liquid sample were detected. The PIXE method used in this study showed outstanding properties for analyzing the liquid sample.

A preparation method making use of liquid nitrogen combined with a powdered-internal-standard method has been established for seaweed and plant samples, whose elemental concentration has been attracting attention in various research fields. It is found that a powdered-internal-standard method developed by us is applicable to the powdered samples treated with liquid nitrogen with good accuracy and reproducibility. The results were compared with those obtained by direct-powder method and by chemical-ashing method and good agreement was obtained. In addition, it is found that the whole sample of large quantities was almost uniformized by this preparation method. Moreover, it becomes possible to obtain concentrations of all the concerned elements including iodine, chlorine and bromine, which are essential elements in the fields of life-sciences and are difficult to be analyzed by the chemical-ashing method. It is expected that the application to other biological samples is also promising.

Environmental samples (rice, soil, river soil and water, running water, pine needle, milk and grass) are collected from the area surrounding Kaya Memorial Takizawa Laboratory (radioisotope waste treatment laboratory) neighboring Nishina Memorial Cyclotron Center for detection of radionuclide in those. We examine annual variations of elemental concentrations in two kinds of environmental samples (pine needle and grass) collected during 5-years period. These were prepared using nitric acid ashing method and analyzed using ordinal vacuum PIXE for detection of the elemental concentration. The result indicates that the concentrations of potassium and phosphorous in grass change according as fertilizer. This is the primary study. The results of annual variations of elemental concentrations in other environmental samples will be described in another paper in the near future.

Environmental samples (rice, soil, river soil and water, running water, pine needle, milk and grass) are collected from the area surrounding Kaya Memorial Takizawa Laboratory (radioisotope waste management laboratory) neighboring Nishina Memorial Cyclotron Center for detection of radionuclides in them. Rice, which is the most important diet for Japanese, was prepared using a nitric acid ashing and analyzed using ordinary vacuum PIXE for detection of the elemental concentration. Comparison of potassium-40 between the detected value using Ge radiation detector and the analyzed value using PIXE was carried out for accuracy. We examine the change of elemental concentration in rice samples harvested in the different rice paddies in 2001 and in the same rice paddy during 13-year period. There is little change in those.

We have measured concentration of multi elements including fluorine in mushrooms collected in Iwate prefecture, Japan. As a result, it was confirmed that the sample preparation method, which was established for the plant samples, is applicable to the mushroom samples and the elemental concentration was obtained in good accuracy and reproducibility. Moreover, it becomes clear that the mushroom takes a specific element selectively depending on its species, and it is found that to analyze various kinds of mushrooms is of great use as a way of monitoring environmental pollution. Fluorine concentration is found to be 7-68 ppm in the mushroom samples. However, clear correlation of fluorine and other elements was not observed in each sample in this study.

As a part of research project for food risk assesment in Asian countries, we have collected a variety of samples including dairy products from Mongolia for PIXE analysis. However, some kinds of milk products or fats such as butter, margarine, mayonnaise and cream are often hard to be homogenized with internal standards because of their viscosity and oiliness, which makes their sample preparation a tiresome work. We have tried to develop efficient preparation and measurement methods for in-air PIXE analysis of those samples. For butter and margarine, liquid internal standard method was taken after melting them with water bath. Pasty samples like mayonnaise and cream were mixed with liquid standard in agate mortar. The applicability of these methods was examined by checking homogeneity of so prepared samples on the basis of Ca concentration. Along with the internal standard methods, a standard-free method has also been worked out for those fatty samples. The obtained results have been fairly satisfactory and we have applied the methods to the Mongolian dairy samples.

In order to maintain homeostasis and consequent optimal cell functioning and integrity and/or to avoid toxicity, proper allocation of elements at organ, tissue, cellular and subcellular level is needed. Studies of element localization are therefore crucial to reveal the mechanisms of element trafficking and also tolerance and toxicity. Moreover, studies of localization and speciation of trace elements in grains of staple crops are also of high applicative value, allowing one to determine major and trace element concentrations in different grain tissues without possible contamination.

In the last decade, a remarkable progress has been made in the development and application of different 2D imaging techniques in complex biological systems, especially in the sense of improved lateral resolution and sensitivity. The superiority of micro-PIXE over other 2D imaging techniques lies in its wide elemental range (from sodium (Na) to uranium (U)), high elemental sensitivity below micron spatial resolution and fully quantitative element concentration analysis.

The aim of this review is to summarize the latest development of micro-PIXE for imaging of the distribution of major and trace elements in crop plants with emphasis on sample preparation methodologies and post-imaging analysis. Case studies of element localization in the grains of major crop plants are also presented.

Quantitative analysis of powder sample, soil, ash and so on, which consists of rich heavy metal elements that are not decomposed easily with acid or alkali was attempted. Usually, powder sample was ground with an agate mortar, mixed with binding material cellulose and pelletized for quantitative PIXE analysis. However, the resulting pellet target is thick. Accordingly, when heavy elements are included in sample, it gives effect on PIXE spectrum. Namely, matrix effect arises on it. So firstly, a fixed quantity of molybdenum was added into sample and mixed as standard material in order to determine the concentration of the most typical element, iron included in sample. Then the mixed powder were pelletized and analyzed to determine the concentration of iron. Next, original powder sample was pushed on a backing film to make thin target, and the thin target was analyzed as internal standard of determined iron by ordinary PIXE analysis method. In the result, concentrations of major elements of powder sample were determined quantitatively.

The preparation of a biological sample using a microtome cryostat was attempted. The biological specimen was previously frozen with a freezing compound and an optimum section thickness was cut for PIXE analysis. First, bovine liver powder which was made into a paste with indium solution as an internal standard was prepared using the sectioning method. The concentrations of trace elements including volatile elements in the sample were determined and agreed with the certified values. Next, a mouse liver was prepared using the sectioning method. A polyphenylene sulfide (PPS) film containing a constant areal density of sulfur was used as a backing material for quantitative analysis. The concentrations of trace elements in a mouse liver prepared using the sectioning method were compared with those using the ordinary nitric acid method. The concentrations of some volatile elements were determined only in the sample obtained using the sectioning method. The preparation method using a microtome cryostat can be used to prepare a biological sample for PIXE analysis.

Laser-induced breakdown spectroscopy (LIBS) is an analytical spectroscopy technique that offers precise quantitative chemical analysis using high energy laser pulse. Although LIBS has been linked as an analytical technique with no sample preparation, this case may be a boundary in preventing it from being a more advanced technique. Regardless of LIBS countless contributions in providing measurements for solid samples, the future applications of LIBS can be explored with the aid of sample preparation methods. This review highlights the previous works of researchers that have proposed and improved various configuration methods specifically targeting to upgrade the LIBS measurements of liquid samples.

Dielectrophoresis (DEP) force is generated by dielectrically polarized particles in non-uniform electrical fields. In this paper, we report the use of DEP in microfluidic sample preparation. The chip uses DEP force to concentrate mammal cells and magnetic beads, in order to extract and purify mRNA from these cells. Both the mammal cells and magnetic beads exhibit negative DEP properties and are concentrated in the same region in the electrical field ie. regions of weaker electrical field of the chip. Therefore, the magnetic beads coated with Oligo (dT) can easily capture mRNA released from the cells when cell is lysed by chemical lyse. Thus a high mRNA yield can be obtained. Silicon is used to make the chip channel and the DEP electrodes. The working principle of the micro-fluidic chip, its fabrication process and experiment results are described in this report.