Toshinari Ichihashi

Enhancement of In Vivo Anticancer Effects of Cisplatin by Incorporation Inside Single-Wall Carbon Nanohorns

Cisplatin (CDDP) was incorporated inside single-wall carbon nanohorns with holes opened (SWNHox) by a nanoprecipitation method that involved dispersion of CDDP and SWNHox in a solvent followed by the solvent evaporation. The incorporated CDDP quantity increased from the previously reported value of 15 to 46%, and the total released quantity of CDDP also increased from 60 to 100% by changing the solvent from dimethylformamide to water. Concurrently, in vitro anticancer efficiency of CDDP@SWNHox increased to 4-6 times greater than that of the intact CDDP. In vivo, CDDP@SWNHox intratumorally injected to transplanted tumors of mice suppressed the tumor growth more than the intact CDDP. We observed that CDDP@SWNHox adhered to the cell surfaces in vitro and stayed within the tumor tissues in vivo. Therefore, we think that the CDDP released from SWNHox realized high concentrations locally at the cells in vitro and in the tissues in vivo and could efficiently attack the tumor cells. We also found that SWNHox itself had an in vivo anticancer effect, which might increase the anticancer activities of CDDP@SWNHox.

Preparation of freestanding GaN wafers by hydride vapor phase epitaxy with void-assisted separation

We have developed a novel technique for preparing large-scale freestanding GaN wafers. Hydride vapor phase epitaxy (HVPE) growth of thick GaN layer was performed on a GaN template with a thin TiN film on the top. After the cooling process of the HVPE growth, the thick GaN layer was easily separated from the template by the assistance of many voids generated around the TiN film. As a result, a freestanding GaN wafer was obtained. The wafer obtained had a diameter of 45 mm, and a mirror-like surface. The-full-width-at-half-maximum (FWHM) of (0002) and (1010) peaks in the X-ray rocking curve profile were 60 and 92 arcsec, respectively. The dislocation density was evaluated at 5×106 cm-3 by etch pit density measurement.

Preparation of high-grade carbon nanotubes by hydrogen arc discharge

Fine and long multiwalled carbon nanotubes attached with less carbon nanoparticles were prepared by d.c. arc discharge plasma of graphite electrodes in hydrogen gas. These high-grade carbon nanotubes grew on the central part of the cathode as a carbon deposit like black soot. They were mainly observed by a scanning electron microscope and subsequently by a high resolution transmission electron microscope. By comparing with helium and methane gases, the predominance of the use of hydrogen gas as the environmental gas is discussed. A new type of carbon allotrope, namely petal-like graphite sheets consisting of a number of interlaced graphene sheets, was also found in the outside region surrounding the central cathode deposit.

SINGLE-WALL CARBON NANOTUBE FORMATION BY LASER ABLATION USING DOUBLE-TARGETS OF CARBON AND METAL

Abstract During laser ablation to form single-wall carbon nanotubes, the composition at the surface of a target composed of C, Ni and Co became metal-rich and the yield of single-wall carbon nanotubes decreased. This problem was solved by applying double-target laser ablation where separate carbon and metal-alloy targets were simultaneously irradiated by the laser light.

Effect of oxidation on single-wall carbon nanotubes

Abstract Two common methods of oxidation, gas-phase oxidation by heat treatment in oxygen gas and liquid-phase oxidation using nitric acid, were applied to single-wall carbon nanotubes (SWNT). The heat treatment in oxygen showed that thinner SWNTs burn more quickly. The nitric acid treatment showed that SWNTs are relatively inert to oxidation using acids. When the nitric acid treated samples were further oxidized by heat treatment in oxygen, selective oxidation of thinner SWNTs occurred.

Free-space-wiring fabrication in nano-space by focused-ion-beam chemical vapor deposition

Focused-ion-beam chemical vapor deposition (FIB-CVD) is an excellent technology for forming three-dimensional nanostructures. Various diamond-like-carbon (DLC) free-space-wirings have been demonstrated by FIB-CVD using a computer-controlled pattern generator, which is a commercially available pattern generator for electron-beam (EB) lithography. The material composition and crystal structure of DLC free-space-wiring were studied by transmission-electron microscopy and energy-dispersive x-ray spectroscopy. As a result, it became clear that DLC free-space-wiring is amorphous carbon containing a Ga core in the wire. Furthermore, the electrical resistivity measurement of DLC free-space-wiring was carried out by two terminal electrodes. Au electrodes were fabricated by EB lithography and a lift-off process. The electrical resistivity was about 100 Ω cm at room temperature.

Variation in Tc, structure and oxygen content in Tl2Ba2CuO6 and their correlations

Abstract The preparation condition of Tl 2 Ba 2 CuO 6 (2201 compound) and its properties including superconductivities and structural variations were studied. Preparation at relatively low heat-treatment temperatures produced the 2201 compound with an orthorhombic symmetry, while heat-treatment above 840°C produced a tetragonal symmetry. It was revealed that the appearance of superconductivity was independent of the structural symmetry, and was strongly affected by oxygen content. Decrease of oxygen content by quenching or Ar-annealing increased the superconducting transition temperatures up to about 70 K. A positive correlation between T c and the c -axis length was also found for all samples including both orthorhombic and tetragonal structures.

Biodistribution and Ultrastructural Localization of Single-Walled Carbon Nanohorns Determined In Vivo with Embedded Gd2O3 Labels

Single-walled carbon nanohorns (SWNHs) are single-graphene tubules that have shown high potential for drug delivery systems. In drug delivery, it is essential to quantitatively determine biodistribution and ultrastructural localization. However, to date, these determinations have not been successfully achieved. In this report, we describe for the first time a method that can achieve these determinations. We embedded Gd(2)O(3) nanoparticles within SWNH aggregates (Gd(2)O(3)@SWNHag) to facilitate detection and quantification. Gd(2)O(3)@SWNHag was intravenously injected into mice, and the quantities of Gd in the internal organs were measured by inductively coupled plasma atomic emission spectroscopy: 70-80% of the total injected material accumulated in liver. The high electron scattering ability of Gd allows detection with energy dispersive X-ray spectroscopy and facilitates the ultrastructural localization of individual Gd(2)O(3)@SWNHag with transmission electron microscopy. In the liver, we found that the Gd(2)O(3)@SWNHag was localized in Kupffer cells but were not observed in hepatocytes. In the Kupffer cells, most of the Gd(2)O(3)@SWNHag was detected inside phagosomes, but some were in another cytoplasmic compartment that was most likely the phagolysosome.

Electron beam induced selective etching and deposition technology

W deposition, using a WF6 source by electron beam induced surface reaction, has been studied by Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The initial growth process has been observed in situ by AES and TEM. As a result, it became clear that a growth rate for W is ∼1 A/min at 2×10−7 Torr and β‐W clusters are formed by electron beam irradiation of the WF6 adlayer. Moreover, it has been observed that W layers are formed by coalescing the W clusters by electron beam irradiation at 5×10−7 Torr WF6 gas pressure. Furthermore, a nanostructure involving a W rod with a 15‐nm diameter has been demonstrated by using electron beam induced surface reaction. Direct writing onto Si, GaAs, and poly(methylmethacrylate) (PMMA) resist have been demonstrated by electron beam induced surface reaction using XeF2, Cl2, and ClF3 sources. The electron beam stimulated etched depth is proportional to the electron dose. A 0.5‐μm linewidth Si and PMMA resist patterns have been fabricated at 4×10−3 a...

In situ observation on electron‐beam‐induced chemical vapor deposition by transmission electron microscopy

W deposition, using a WF6 source and electron‐beam‐induced surface reaction, has been studied by transmission electron microscopy (TEM). The initial growth process has been observed in situ by TEM. As a result, it became clear that β‐W clusters are formed by electron beam irradiation of the WF6 adlayer. Moreover, it has been observed that W layers are formed by coalescing the W clusters by electron beam irradiation at 5×10−7 Torr WF6 gas pressure. Furthermore, a nanostructure involving a W rod with 15 nm diameter has been demonstrated by using electron‐beam‐induced surface reaction.