Papers by Author: Fumio Watari

Abstract: The risks of nanomaterials for future generations should be elucidated. Thus, it is important to establish an experimental method to accurately examine embryotoxicity. We have conducted an in vitro embryotoxicity test with mouse ES cells to examine the embryotoxicities of various nanomaterials. In this study, the C60 fullerene did not influence the differentiation of ES-D3 cells and "non embryotoxicity". In the future, the biological safety should be comprehensively examined by improving dispersion in medium.

Abstract: The reports on cytotoxic studies of carbon nanotubes (CNTs) increased exponentially. In the present study, we investigate murine macrophage RAW264.7 cell response for the CNTs immobilized on a polystyrene substrate. We prepared CNT-coated dishes, and estimate the interaction of RAW264.7 cells with CNTs by cell adhesion, proliferation assay, and measurement of TNF-α production. As a result, the highest cell adhesion and proliferation was observed on a commercially cell culture polystyrene dish, while CNT-coated dish indicate slightly lower activity of them. Moreover, amount of production of TNF-α on the CNT-coated dishes was considerable lower than that in the case of lipopolysaccharide (LPS) addition as a control. These results indicated that CNT-coated dishes could not show strong cytotoxicity for RAW264.7 cells in vitro.

Abstract: Cytotoxicity and cell behavior to micro / nanoparticles of TiO₂ and CuO was evaluated using the viability measurement and time-lapse observation. After cultured, osteoblastic cells MC3T3-E1 were exposed to particles. After 24 hour exposure, their morphology was observed using a SEM and the viability was measured. Cells exposed to TiO₂ indicated no or very low decrease of viability. The results were independent of the particle size. On the other hand, the viability of cells exposed to CuO decreased with the concentration, and showed the size dependence. The nanosized CuO indicated higher toxicity compared with micro-sized one. Dynamic behavior of cells exposed to nanoparticles, was succeeded to observe in a time-lapse method for 24 hours. The observation showed that the cells exposed to CuO became dead after forming a spherical shape. This is consistent with the image taken by SEM. Time-lapse observation made it possible to see the dynamic reaction process from cell contact to particles at first, the following cell activity response and finally to cell death, which revealed a considerably different morphology from the static cell observed after fixation by conventional method.

Abstract: We succeeded in determination the biodistribution of several nano-sized particles administered to mice through the tail vein. After administration, these particles were observed in the lung, liver and spleen. The distribution behaviors depend upon not only chemical species but also the particles size. To estimate their cytocompatibility, these particles were exposed to osteoblastic cell at several concentrations. When the concentration reached at 10 ppm, their viability remained at 80% or more even nano-sized particle contained rare earth element. Only CuO particles indicated the viability decrease. The effect depended on the particle size. These results suggested that the chemical species played a dominant key in the biodistribution and biocompatibility of nanoparticles compared with the size-effect.

Abstract: Carbon nanotubes (CNTs) have excellent chemical, physical, and biological properties such as strong cell adhesion, protein adsorption and cell proliferation in vitro. Excellent osteocompatibility for the CNT monolith was also reported in vivo. The purpose of this study was to evaluate the effects of anodized titanium coated with multiwalled CNTs (MWCNTs) on human osteosarcoma Saos2 cells and bone tissue. Saos2 cells on CNT-Ti showed excellent proliferation with extension of cell morphology in all directions. CNT-Ti wire was implanted in the bone marrow of femurs of rats. At 2 weeks after surgery, histological investigations revealed that bone tissue attached to the surface of the CNT-Ti directly. Thus the surface modification of anodized Ti by MWCNTs can be effective for bone formation.

Abstract: For application of carbon nanotubes (CNTs) as biomaterials, it is important to clarify the interaction between CNTs and proteins, which may affect on cell proliferation and differentiation. In this study, the adsorption behavior was investigated for representative proteins, bovine serum albumin, lysozyme and fetal bovine serum by using chromatography system. It was also aimed whether the different treatment conditions of CNTs affected the adsorption of proteins. CNTs used for this study had a straight shape and about 70nm in a diameter from SEM observation. There was not much difference between untreated and treated CNTs from SEM images. In chromatography experiments, all the proteins of albumin, lysozyme and serum were eluted immediately after injected to the column of untreated CNTs. Second elution appeared after buffer was changed from phosphate saline buffer to 25mM sodium hydroxide (NaOH). The same tendency was confirmed for CNTs with only acid treatment. However the eluted peaks became remarkably smaller after the column was changed to CNTs with thermal and twice acid treatments. These results indicated that treatment conditions for CNTs affected the adsorption behavior of proteins.

Abstract: In this study, we succeeded in preparation and characterization of two types of biocompatible polymer-coated inorganic nanoparticles (cupper and silicone oxide). As a biocompatible polymer, gelatin and poly(lactic acid) were used. For determination of their biodistribution, the obtained particles were administered to mice through the tail vein. After administration, the particles in some organs were determined with energy-dispersed X-ray spectrometer. The cupper nanoparticles were observed in the lung and kidney, while the silica particles were in the lung, liver and spleen. The distribution behaviors were quite different from non-polymer coated nanoparticles

Abstract: Carbon nanotubes (CNT) and their derivatives with different structure and compositions have unique features. In the present study, cell proliferation was performed on various nanotubes such as single walled CNTs, multiwalled CNTs and imogolite which is nanotubes of aluminosilicate. SEM observation of the growth of osteoblast-like cells cultured on CNTs showed the morphology fully developed for the whole direction, which was different from that extended to the one direction on the usual scaffold. Numerous filopodia were grown from cell edge, extended far long and combined with CNT meshwork. Apatite precipitation in simulated body fluid, affinity for proteins and saccharides, and nanosize meshwork structure with large porosity would be the properties responsible for these cell adhesion and growth. Imogolite showed the similar properties to CNTs. Nanotubes could be the favorable materials for biomedical applications.

Abstract: Nanoparticles may invade directly into the internal body through the respiratory or digestive system and diffuse inside body. The behavior of nanoparticles in the internal body is also essential to comprehend for the realization of DDS. Thus it is necessary to reveal the internal dynamics for the proper treatments and biomedical applications of nanoparticles. In the present study the plural methods with different principles such as X-ray scanning analytical microscope (XSAM), MRI and Fluorescent microscopy were applied to enable the observation of the internal diffusion of micro/nanoparticles in the (1) whole body level, (2) inner organ level and (3) tissue and intracellular level. Chemical analysis was also done by ICP-AES for organs and compared with the results of XSAM mapping.

Abstract: Internal distributions of several inorganic microparticles administered into the tail vein of mice were determined using a Scanning X-ray analytical microscopy and energy-dispersed X-ray spectroscopy. After administration through the tail vein of mice, the particles circulated by blood flow then reach some organs and temporally remained. In this study, we determined that the distribution behaviors in body depend upon the chemical species and the size.