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Naka ku, Japan

Akasaka T.,Hokkaido University | Yokoyama A.,Hokkaido University | Matsuoka M.,Hokkaido University | Hashimoto T.,Meijo Nano Carbon Co. | Watari F.,Hokkaido University

Induced pluripotent stem (iPS) cells have attracted worldwide interest. However, there have been only a few studies investigating effective culture substrates for feeder-free culturing for the maintenance of iPS cells. In this study, we cultured mouse iPS cells under feeder-free conditions on carbon nanotube (CNT)-coated dishes and then evaluated the colony morphology and differentiation state of the cells on the dishes. After 5 d of cultivation in a medium containing 15% fetal bovine serum (FBS) and leukemia inhibitory factor (LIF), the colonies on thick films of multi-walled CNTs (MWCNTs) were observed to be hemiround; further, the cells expressed early undifferentiation markers. On the other hand, the colonies on a cell culture polystyrene dish and a collagen-coated polystyrene dish showed indistinct outline and spread well, and most spreading cells only weakly expressed early undifferentiation markers. These results indicate that the thick films of MWCNTs could maintain hemiround colonies and undifferentiated state of mouse iPS cells cultured under feeder-free conditions. © 2011 Elsevier Ltd. All rights reserved. Source

Zaka M.,University of Oxford | Ito Y.,University of Oxford | Wang H.,University of Oxford | Yan W.,University of Oxford | And 10 more authors.
ACS Nano

Electron paramagnetic resonance of single-walled carbon nanotubes (SWCNTs) has been bedevilled by the presence of paramagnetic impurities. To address this, SWCNTs produced by laser ablation with a nonmagnetic PtRhRe catalyst were purified through a multiple step centrifugation process in order to remove amorphous carbon and catalyst impurities. Centrifugation of a SWCNT solution resulted in sedimentation of carbon nanotube bundles containing clusters of catalyst particles, while isolated nanotubes with reduced catalyst particle content remained in the supernatant. Further ultracentrifugation resulted in highly purified SWCNT samples with a narrow diameter distribution and almost no detectable catalyst particles. Electron paramagnetic resonance (EPR) signals were detected only for samples which contained catalyst particles, with the ultracentrifuged SWCNTs showing no EPR signal at X-band (9.4 GHz) and fields < 0.4 T. © 2010 American Chemical Society. Source

Al-Zubaidi A.,Nagoya Institute of Technology | Inoue T.,Nagoya Institute of Technology | Matsushita T.,Nagoya Institute of Technology | Ishii Y.,Nagoya Institute of Technology | And 2 more authors.
Journal of Physical Chemistry C

The electrochemical behavior of highly crystallized single-walled carbon nanotubes (SWCNTs), having a small diameter distribution, is investigated by cyclic voltammetry (CV), using triethylmethylammonium tetrafluoroborate in propylene carbonate as an electrolyte. Unlike the CV curves previously observed by other researchers and referred to as the "butterfly" shape, the CV curve observed in the present study shows large bulges on both sides of the rest potential, thereby resembling a dumbbell. By comparison of the electronic density of states (DOS) of SWCNTs and the dumbbell CV shape, it was determined that the drastic increase of current in the dumbbell shape can be explained by the van Hove singularity in the DOS of the semiconducting SWCNTs in the sample. To validate the explanation, we performed separation of metallic and semiconducting SWCNTs by the density gradient ultracentrifugation method and measured CV curves of the two separated samples. As was expected, the two SWCNT samples showed completely different CV profiles corresponding to each DOS shape. In addition, ion adsorption inside the nanotube is discussed with attention to the change in CV curves with increasing sweep rate. © 2012 American Chemical Society. Source

Akasaka T.,Hokkaido University | Yokoyama A.,Hokkaido University | Matsuoka M.,Hokkaido University | Hashimoto T.,Meijo Nano Carbon Co. | Watari F.,Hokkaido University
Materials Science and Engineering C

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. © 2009 Elsevier B.V. All rights reserved. Source

Meijo University, Takasago Industry Co., Masuoka Ceramic Materials Co. and Meijo Nano Carbon Co. | Date: 2010-02-02

A process and an apparatus for producing a composite material utilize a rotatable hollow body that is inclined with an upstream side being higher than a downstream side. A reaction zone is defined within an elongated chamber in the hollow body. Protrusions inwardly extend from an inner peripheral wall of the hollow body adjacent to the reaction zone. Base material is input into the chamber via a base material introduction port and a carbon source vapor is input into the chamber via a carbon source supply port. A heater heats the reaction zone to a temperature at which carbon nanotubes form on the base material from the carbon source vapor. The protrusions catch base material disposed on the inner peripheral wall of the hollow body when the hollow body rotates and then drop the base material through the reaction zone so that the base material contacts the carbon source vapor.

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