Kunio Uchida

Conical beams from open nanotubes

Electron guns are indispensable devices that are widely used in household and industrial appliances. Field electron-emitting sources (which emit electrons by tunnelling effects in electric fields), with their small size, small energy spread, high current density and no requirement for heat, have distinct advantages over thermionic emitters. We have made a field electron emitter from hollow, open-ended carbon nanotubes.

Gene expression profiles in rat lung after inhalation exposure to C60 fullerene particles.

Concern over the influence of nanoparticles on human health has risen due to advances in the development of nanotechnology. We are interested in the influence of nanoparticles on the pulmonary system at a molecular level. In this study, gene expression profiling of the rat lung after whole-body inhalation exposure to C(60) fullerene (0.12mg/m(3); 4.1x10(4) particles/cm(3), 96nm diameter) and ultrafine nickel oxide (Uf-NiO) particles (0.2mg/m(3); 9.2x10(4) particles/cm(3), 59nm diameter) as a positive control were employed to gain insights into these molecular events. In response to C(60) fullerene exposure for 6h a day, for 4 weeks (5 days a week), C(60) fullerene particles were located in alveolar epithelial cells at 3 days post-exposure and engulfed by macrophages at both 3 days and 1 month post-exposures. Gene expression profiles revealed that few genes involved in the inflammatory response, oxidative stress, apoptosis, and metalloendopeptidase activity were up-regulated at both 3 days and 1 month post-exposure. Only some genes associated with the immune system process, including major histocompatibility complex (MHC)-mediated immunity were up-regulated. These results were significantly different from those of Uf-NiO particles which induced high expression of genes associated with chemokines, oxidative stress, and matrix metalloproteinase 12 (Mmp12), suggesting that Uf-NiO particles lead to acute inflammation for the inhalation exposure period, and the damaged tissues were repaired in the post-exposure period. We suggest that C(60) fullerene might not have a severe pulmonary toxicity under the inhalation exposure condition.

Pulmonary toxicity of well-dispersed multi-wall carbon nanotubes following inhalation and intratracheal instillation

Abstract Multi-walled carbon nanotubes (MWCNTs), dispersed in suspensions consisting mainly of individual tubes, were used for intratracheal instillation and inhalation studies. Rats intratracheally received a dose of 0.2 mg, or 1 mg of MWCNTs and were sacrificed from 3 days to 6 months. MWCNTs induced a pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups, and presence of small granulomatous lesion and persistent neutrophil infiltration in the high-dose groups. In the inhalation study, rats were exposed to 0.37 mg/m3 aerosols of well-dispersed MWCNTs (>70% of MWCNTs were individual fibers) for 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inhalation exposures delivered less amounts of MWCNTs into the lungs, and therefore less pulmonary inflammation responses was observed, as compared to intratracheal instillation. The results of our study show that well-dispersed MWCNT can produce pulmonary lesions, including inflammation.

Inflammogenic effect of well-characterized fullerenes in inhalation and intratracheal instillation studies

BackgroundWe used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study. Fullerenes were individually dispersed in distilled water including 0.1% Tween 80, and the diameter of the fullerenes was 33 nm. These suspensions were directly injected as a solution in the intratracheal instillation study. The reference material was nickel oxide in distilled water. Wistar male rats intratracheally received a dose of 0.1 mg, 0.2 mg, or 1 mg of fullerenes and were sacrificed after 3 days, 1 week, 1 month, 3 months, and 6 months. In the inhalation study, Wistar rats were exposed to fullerene agglomerates (diameter: 96 ± 5 nm; 0.12 ± 0.03 mg/m3; 6 hours/days for 5 days/week) for 4 weeks and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inflammatory responses and gene expression of cytokine-induced neutrophil chemoattractants (CINCs) were examined in rat lungs in both studies.ResultsIn the intratracheal instillation study, both the 0.1 mg and 0.2 mg fullerene groups did not show a significant increase of the total cell and neutrophil count in BALF or in the expression of CINC-1,-2αβ and-3 in the lung, while the high-dose, 1 mg group only showed a transient significant increase of neutrophils and expression of CINC-1,-2αβ and -3. In the inhalation study, there were no increases of total cell and neutrophil count in BALF, CINC-1,-2αβ and-3 in the fullerene group.ConclusionThese data in intratracheal instillation and inhalation studies suggested that well-dispersed fullerenes do not have strong potential of neutrophil inflammation.

Expression of cytokine-induced neutrophil chemoattractant in rat lungs by intratracheal instillation of nickel oxide nanoparticles

Since nanoparticles easily agglomerate to form larger particles, it is important to maintain the size of their agglomerates at the nano-level to evaluate the harmful effect of the nanoparticles. We prevented agglomeration of nickel oxide nanoparticles by ultrasound diffusion and filtration, established an acute exposure model using animals, and examined inflammation and chemokine expression. The mass median diameter of nickel oxide nanoparticle agglomerates suspended in distilled water for intratracheal instillation was 26 nm (8.41 nm weighted average surface primary diameter). Male Wistar rats received intratracheal instillation of nickel oxide nanoparticles at 0.1 mg (0.33 mg/kg) or 0.2 mg (0.66 mg/kg), and were dissected 3 days, 1 week, 1 month, 3 months, and 6 months after the instillation. The control group received intratracheal instillation of distilled water. Three chemokines (cytokine-induced neutrophil chemoattractant-1 (CINC-1), CINC-2αβ, and CINC-3) in the lung tissue and bronchoalveolar lavage fluid (BALF) were determined by quantitative measurement of protein by ELISA. Both CINC-1 and CINC-2αβ concentration was elevated from day 3 to 3 months in lung tissue and from day 3 to 6 months in BALF. On the other hand, CINC-3 was elevated on day 3 in both lung tissue and BALF, and then decreased. The total cell and neutrophil counts in BALF were increased from day 3 to 3 months. In lung tissue, infiltration of mainly neutrophils and alveolar macrophages was observed from day 3 to 6 months in alveoli. These results suggest that CINC was involved in lung injury by nickel oxide nanoparticles.

Expression of inflammation-related cytokines following intratracheal instillation of nickel oxide nanoparticles

Abstract The objective of this study was to examine what kinds of cytokines are related to lung disorder by well-dispersed nanoparticles. The mass median diameter of nickel oxide in distilled water was 26 nm. Rats intratracheally received 0.2 mg of nickel oxide suspended in distilled water, and were sacrificed from three days to six months. The concentrations of 21 cytokines including inflammation, fibrosis and allergy-related ones were measured in the lung. Infiltration of alveolar macrophages was observed persistently in the nickel oxide-exposed group. Expression of macrophage inflammatory protein-1α showed a continued increase in lung tissue and broncho-alveolar lavage fluid (BALF) while interleukin-1α (IL-1α), IL-1β in lung tissue and monocyte chemotactic protein-1 in BALF showed transient increases. Taken together, it was suggested that nano-agglomerates of nickel oxide nanoparticles have a persistent inflammatory effect, and the transient increase in cytokine expression and persistent increases in CC chemokine were involved in the persistent pulmonary inflammation.

Adsorption of thiophene on an MoS2 cluster model catalyst: ab initio density functional study

Abstract Adsorption of thiophene on the coordinately unsaturated Mo atom on the ( 3 0 3 0 ) plane of an Mo16S32 cluster has been investigated to develop fundamental understanding of the adsorption sites of MoS2 catalysts in the hydrotreatment process. By using the density functional theory (DFT) method, full geometry optimization and vibrational analysis of the thiophene/cluster complex have been carried out. Adsorption energies and vibrational frequencies for different adsorption configurations have been computed. The thiophene molecule remains almost flat in the upright configuration, but becomes bent in the parallel configurations. The CS distances become longer for all the adsorption configurations, indicating that activation of the CS bond occurs. The CC and CC distances become shorter and longer for the upright configuration, respectively. For the parallel configurations, the change of distances is in the opposite direction. The most stable configuration is the bridged and rotated parallel geometry. It is easy to distinguish whether thiophene is adsorbed in the upright or parallel coordination on sulfided Mo catalysts by means of the vibrational frequencies of adsorbed thiophene. With respect to the calculated vibrational frequencies of free thiophene, the ν(CC)asym and ν(CC)sym bands shift to higher frequencies for the upright configuration, whereas they shift to lower for the parallel configurations.

Filtration of Multi-Walled Carbon Nanotube Aerosol by Fibrous Filters

Filtration efficiency of multi-walled carbon nanotube (MWCNT) aerosol by fibrous filter was evaluated experimentally. Mono-mobility test aerosols with electrical mobility diameter of 100, 200, and 300 nm were generated by the atomization of MWCNT aqueous suspension followed by mobility classification with a differential mobility analyzer (DMA). By analyzing the shape of classified aerosol particles under a scanning electron microscope, it was found that the DMA-classified 300 nm particles were fibrous in shape and had uniform diameter of about 60 nm and length of 2.1 micrometer. On the other hand, 100 nm and 200 nm particles contained a fairly large amount of multiply charged fibrous particles with a larger diameter. These test aerosols were challenged to a medium performance fibrous filter at various filtration velocities. As a result, fibrous particles were captured by fibrous filter at a higher collection efficiency than the spherical particles with the same mobility. By analyzing the single fiber capturing efficiency, interception incorporating the rotation of fibrous particles is found to be the dominant capturing mechanism for the fibrous particles in the studied size range.

Synthesis of crystalline boron nanowires by laser ablation

Crystalline boron nanowires with tetragonal structure have been synthesized based on laser ablation of a B/NiCo target; the nanowires are sometimes single crystals and have a droplet at one end of the nanowire; the droplet contains B, Ni and Co elements, which indicates that the vapor-liquid-solid (VLS) mechanism may play a key role in the growth of the boron nanowires.

Pathological features of rat lung following inhalation and intratracheal instillation of C(60) fullerene.

We evaluated the pulmonary pathological features of rats that received a single intratracheal instillation and a 4-week inhalation of a fullerene. We used fullerene C60 (nanom purple; Frontier Carbon Co. Ltd, Japan) in this study. Male Wistar rats received intratracheal dose of 0.1, 0.2, or 1 mg of C60, and were sacrificed at 3 days, 1 week, 1 month, 3 months, 6 months, and 12 months. In the inhalation study, Wistar rats received C60 or nickel oxide by whole-body inhalation for 6 h/day, 5 days/week, 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. During the observation period, no tumors or granulomas were observed in either study. Histopathological evaluation by the point counting method (PCM) showed that a high dose of C60 (1 mg) instillation led to a significant increase of areas of inflammation in the early phase (until 1 week). In the inhalation study of the C60-exposed group, PCM evaluation showed significant changes in the C60-exposed group only at 3 days after exposure; after 1 month, no significant changes were observed. The present study demonstrated that the pulmonary inflammation pattern after exposure to well-characterized C60 via both intratracheal and inhalation instillation was slight and transient. These results support our previous studies that showed C60 has no significant adverse effects in intratracheal and inhalation instillation studies.