Development of novel bioactive composites by electrophoretic deposition

Electrophoretic deposition (EPD), which is normally available on electric conductive materials, was applied to insulating materials. Wollastonite particles were deposited into the pores of porous alumina and porous ultrahigh molecular weight polyethylene (UHMWPE) substrates by EPD to yield alumina-wollastonite and UHMWPE-wollastonite composites, respectively. These composites were soaked in simulated body fluid (SBF) to evaluate their apatite-forming ability. Apatite was induced from the wollastonite particles, which grew on the surfaces and covered the entire composite surfaces. The bonding strength of the apatite layer to the substrates was as high as 8.9 MPa for alumina and 5.2 MPa for UHMWPE due to an interlocking effect. Thus, the formed alumina-wollastonite and UHMWPE-wollastonite composites should be useful as bone substitutes.     

Wavelength conversion film with glass coated Eu chelate for enhanced silicon-photovoltaic cell performance

In order to improve the conversion efficiency of a silicon-photovoltaic (PV) module, we investigated the combination with a wavelength conversion film (WCF), which consists of Eu chelate particles encapsulated by the sol–gel derived silica glass. The photoluminescence (PL) excitation spectrum of Eu chelate shows that the violet light below 400 nm is effectively converted to the red emission at 613 nm. Since the PV cell has higher sensitivity at the red wavelength region compared to the violet region, Eu chelate is one of the suitable material for a WCF. The diameter of fabricated sol–gel encapsulated Eu chelate was larger than the wavelength of irradiated sunlight, therefore, the transmittance of a WCF decreased with increasing the concentration of Eu chelate. The short circuit current (J_SC) was increased by inserting the the WCF on the front side of Si-PV cell compared to the reference module (glass/ethylene vinyl acetate/WCF without Eu chelate/Si-PV cell/EVA/back-film), and the maximum increase of ΔJ_SC was 1.03 mA/cm² compared to the reference module. However, the maximum ΔJ_SC of fabricated module was almost same as the conventional Si-PV cell due to the refractive index mismatch of each layers.     

Occurrence and profiles of chlorinated and brominated polycyclic aromatic hydrocarbons in waste incinerators

Chlorinated polycyclic aromatic hydrocarbons (CIPAHs) have been reported to occur in urban air. Nevertheless, sources of CIPAHs in urban air have not been studied, due to the lack of appropriate analytical methods and standards. In this study, we measured concentrations of 20 CIPAHs and 11 brominated PAHs (BrPAHs) in fly ash and bottom ash from 11 municipal/hazardous/industrial waste incinerators, using analytical standards synthesized in our laboratory. Concentrations of total CIPAHs and BrPAHs in ash samples ranged from <0.06 to 6990 ng/g and from <0.14 to 1235 ng/g, respectively. The concentrations of CIPAHs were approximately 100-fold higher than the concentrations of BrPAHs. 6-CIBaP and 1-CIPyr were the dominant compounds in fly ash samples. The profiles of halogenated PAHs were similar to the profiles reported previously for urban air. 1-BrPyr was the predominant BrPAH in fly ash. Concentrations of 6-CIBaP, 9,10-Cl2Phe, 9-CIAnt, and 6-BrBaP in fly ash were significantly correlated with the corresponding parent PAH concentrations. Significant correlation between sigmaCIPAH and sigmaPAH concentrations suggests that direct chlorination of parent PAHs is the mechanism of formation of CIPAHs during incineration of wastes; nevertheless, a comparable correlation was not found for BrPAHs. There was no significant correlation between the capacity and temperature of an incinerator and the concentrations of sigmaCl-/BrPAHs in ash samples, although lower concentrations of all halogenated PAHs were found in stoker-type incinerators than in fixed grate-type incinerators. Toxicity equivalency quotients (TEQs) for CIPAHs in ash samples were calculated with CIPAH potencies. Average TEQ concentrations of CIPAHs in fly ash and bottom ash were15800 pg-TEQ/g and 67 pg-TEQ/g, respectively. Our results suggest that the extent of dioxin-like toxicity contributed by CIPAHs in ash generated during waste incineration is similar to that reported previously for dioxins. Waste incineration is an important source of Cl-/BrPAHs in the urban atmosphere.     

Propagation of bovine spermatogonial stem cells in vitro

The access to sufficient numbers of spermatogonial stem cells (SSCs) is a prerequisite for the study of their regulation and further biomanipulation. A specialized medium and several growth factors were tested to study the in vitro behavior of bovine type A spermatogonia, a cell population that includes the SSCs and can be specifically stained for the lectin Dolichos biflorus agglutinin. During short-term culture (2 weeks), colonies appeared, the morphology of which varied with the specific growth factor(s) added. Whenever the stem cell medium was used, round structures reminiscent of sectioned seminiferous tubules appeared in the core of the colonies. Remarkably, these round structures always contained type A spermatogonia. When leukemia inhibitory factor (LIF), epidermal growth factor (EGF), or fibroblast growth factor 2 (FGF2) were added, specific effects on the numbers and arrangement of somatic cells were observed. However, the number of type A spermatogonia was significantly higher in cultures to which glial cell line-derived neurotrophic factor (GDNF) was added and highest when GDNF, LIF, EGF, and FGF2 were all present. The latter suggests that a proper stimulation of the somatic cells is necessary for optimal stimulation of the germ cells in culture. Somatic cells present in the colonies included Sertoli cells, peritubular myoid cells, and a few Leydig cells. A transplantation experiment, using nude mice, showed the presence of SSCs among the cultured cells and in addition strongly suggested a more than 10 000-fold increase in the number of SSCs after 30 days of culture. These results demonstrate that bovine SSC self-renew in our specialized bovine culture system and that this system can be used for the propagation of these cells.     

Fatigue damage monitoring of round shape specimen by acoustic microscopy

Acoustic microscope can detect microstructural features with high resolving power compared to other lower frequency acoustic techniques. Many non-destructive evaluations using acoustic microscope, several of them used in industrial fields, were investigated. However, acoustic measurement of curved surface structure was restricted to basic studies as conventional acoustic microscope system was designed for flat specimen. We have developed a modified acoustic microscope for curved surface specimen testing and have measured acoustic image of round bar specimen. In this study, using this system, velocities of round bar specimen during fatigue test are monitored using the V(z) curve method. Measurement errors depending on curved surface measurement were investigated and it was found that the acoustic velocity tends to increase as fatigue damage increases.     

Synthesis and electrochromic properties of a highly water-soluble hyperbranched polymer viologen

A highly water-soluble hyperbranched polymer with viologen units (HB-1) was synthesized for application to electrochromic (EC) display. Electrochemical and spectroscopic properties of HB-1 were evaluated by absorption spectra and cyclic voltammetry. They were compared with those of a low molecular weight viologen molecule (1). We fabricated a simple EC window by a thin (300-500 nm) solid film of HB-1 and an electrolyte solution to demonstrate the EC behavior. By successively applying opposite bias voltages to it, reversible color changes between colorless and purple were observed with good contrast, whereas blue color was observed for 1 upon reduction. The colored state in HB-1 was ascribed to the generation of radical cation dimer species of viologen units due to high local concentrations in HB-1. When the bias was turned off after achieving the colored state, no fading was observed in the EC window. This result indicates that the radical cation dimer species of HB-1 in solid films were stable against disproportionation or reaction with oxygen even though no active protection was made in this EC window. Since the present EC device has such a memory effect, bias voltage is needed in writing and erasing processes alone, which is very useful in practical applications.     

Thin films of single-walled carbon nanotubes promote human osteoblastic cells (Saos-2) proliferation in low serum concentrations

One strategy used for the regeneration of bone is the development of cell culture substrates and scaffolds that can control osteoblast proliferation and differentiation. In recent investigations, carbon nanotubes (CNTs) have been utilized as scaffolds for osteoblastic cell cultures; however, there are only a few reports describing the proliferation of osteoblastic cells on thin CNT films; in particular, the effects of serum concentration on cell proliferation have not been studied. In the present study, we prepared culture dishes with homogeneous thin or thick films of non-modified CNTs and examined the effect of serum concentrations on human osteoblastic cells (Saos-2) proliferation in these culture dishes. We demonstrated that the ratio of cell proliferation was strongly affected by the concentration of serum. Interestingly, single-walled carbon nanotube (SWNT) thin films were found to be the most effective substrate for the proliferation of Saos-2 cells in low concentrations of serum. Thus, thin SWNT films may be used as an effective biomaterial for the culture of Saos-2 cells in low serum concentrations.     

Development and degradation of graphitic microtexture in carbon nanospheres under a morphologically restrained condition

Graphitic microtexture in carbon nanospheres (CNSs, average diameter = 500–1000 nm) formed by a heat-treatment between 2000 °C and 2900 °C was investigated with XRD, Raman spectrum, SEM and TEM. By the heat-treatment up to 2000 °C, CNS particles in any size were polyhedronized. In the microtexture of polyhedronized CNS particles thus obtained, graphitic stacking structure of aromatic layers was well developed in the polyhedron face regions, while an aggregation of column-like crystallite was confirmed in the polyhedron ridge region. It was also shown that some ridges of CNSs with the average diameter over 700 nm were collapsed by the heat-treatment at 2900 °C. These collapses include an exfoliation of aromatic layers in which the torn layers have hairpin-like microtexture at their ends, and a crack of layer stacks with adjacent layer stacks. According to a direct examination with TEM, it was clarified that a ratio of ridges with either type of damage to a total number of ridges is obviously higher in CNS particles with larger diameter. This phenomenon was discussed in relation to the high crystallinity in the polyhedron face regions and the aggregation of structural defects in the ridge regions.     

The mixed coculture effect of primary rat hepatocytes and bone marrow cells is caused by soluble factors derived from bone marrow cells

Heterospheroids consisting of hepatocytes and bone marrow cells (BMCs) are formed by the mixed coculture of these cells and enhance the expression and maintenance of the liver-specific functions of hepatocytes. Not only the soluble factors derived from these cells, but also functional organoid (heterospheroid) formation, are considered to underlie this coculture effect. Therefore, in the present study, we aimed to clarify the mechanism of this co-culture effect. We performed hepatocyte monoculture with conditioned media prepared from hepatocyte cultures, BMC cultures and a coculture of hepatocytes and BMCs. When using any type of conditioned medium, no hepatocyte spheroids formed, and the hepatocytes formed a monolayer. In addition, an effect for these conditioned media was shown in terms of the albumin production and ammonia metabolism activities of the hepatocytes; conditioned medium from BMCs showed the strongest effect. The monocultured hepatocytes in the conditioned medium derived from BMCs showed equivalent albumin production and ammonia metabolism activities to the cocultured spheroids of hepatocytes and BMCs. Therefore, it was determined that the effect of the coculture of hepatocytes and BMCs was caused by soluble factors derived from BMCs.     

High throughput and exhaustive analysis of diverse lipids by using supercritical fluid chromatography-mass spectrometry for metabolomics

We have developed an analytical system that enables the simultaneous rapid analysis of lipids with varied structures and polarities through the use of supercritical fluid chromatography-mass spectrometry (SFC-MS). The separation conditions for SFC (column, modifier, back pressure, etc.) and the detection conditions for mass spectrometry (ionization method, parameters, etc.) were investigated to develop a simultaneous analytical method for lipid mixtures that included phospholipids, glycolipids, neutral lipids, and sphingolipids. When cyanopropylated silica gel-packed column was used for the separation, all lipids were successfully detected and the analysis time was less than 15 min. The use of an octadecylsilylated column resulted in separation, which was dependent on the differences in the unsaturation of the fatty acid side chains and isomer separation. This system is a powerful tool for studies on lipid metabolomics because it is useful not only as a fingerprinting method for the screening of diverse lipids but also for the detailed profiling of individual components.