Search

Mei Yang,1 Minfang Zhang,1 Hideaki Nakajima,1 Masako Yudasaka,1,2 Sumio Iijima,2 Toshiya Okazaki11Nanotube Application Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan; 2Faculty of Science & Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, JapanIntroduction and objective: With the increase in carbon nanotube-based products on the commercial market, public concern regarding the possible toxicity of these nanomaterials has attracted much attention. Although previous studies found no obvious toxicity related to carbon nanotubes (CNTs), their safety has not been established because long-term evaluation is still needed. In vitro assays are used to understand the toxicity of nanomaterials. However, the data published so far were generated in short-term assays in which cells are continuously exposed to CNTs. Therefore, the objective of this study is to quantitatively assess the relative long-term cytotoxicity and degradation of CNTs after uptake by macrophages.Methods: We used macrophage cell line of RAW 264.7 and primary rat Kupffer cells to investigate macrophage uptake of CNTs as well as their quantity changes up to a relatively late time point after uptake (7 days) by measuring optical absorbance in the near infrared region and Raman spectra of CNTs in the cell lysates. The time-dependent cytotoxicity was evaluated by measuring reactive oxygen species (ROS), glutathione, cell viability, and caspase 3/7 activity in 1–7 days.Results: CNTs were degraded by approximately 25–30% within first 4 days after uptake; however, and no additional degradation occurred for the remainder of the 7-day test period. Generation of ROS by macrophages decreased as CNT degradation occurred, returning to control levels by Day 7. In the meantime, the glutathione level gradually recovered over time. There were no changes in cell viability or caspase 3/7 activation during CNT degradation.Conclusion: These results confirm that degradation of CNTs by macrophages is associated with ROS generation. The data also suggest that CNT cytotoxicity decreases as they are degraded.Keywords: carbon nanomaterials, biodegradation, cytotoxicity, cellular uptake

Katsutoshi Kokubun,1,2 Sachiko Matsumura,1 Masako Yudasaka,3,4 Sumio Iijima,3,4 Kiyotaka Shiba1 1Division of Protein Engineering, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan; 2Department of Clinical Pathophysiology, Tokyo Dental College, Tokyo, Japan; 3Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan; 4Graduate School of Science and Technology, Meijo University, Nagoya, Japan Introduction: Inorganic materials are widely used in medical devices, such as artificial hearts, vessels, and joints, in stents, and as nanocarriers for drug-delivery systems. Carbon nanomaterials are of particular interest due to their biological inertness and their capability to accommodate molecules. Several attempts have been proposed, in which carbon nanomaterials are used as nanocarriers for the systemic delivery of drugs.Materials and methods: We developed a drug-delivery system in which oxidized single-walled carbon nanohorns (oxSWNHs) were immobilized on a titanium (Ti) surface using material-binding peptides to enable localized drug delivery. For this purpose, we utilized a bispecific peptidic aptamer comprising a core sequence of a Ti-binding peptide and a SWNH-binding peptide to immobilize oxSWNHs on Ti.Results: Scanning electron microscopy was used to confirm the presence of oxSWNHs adsorbed onto the Ti surface, and a quartz crystal microbalance was used to evaluate the binding process during oxSWNH adsorption. The oxSWNHs-ornamented Ti substrate was nontoxic to cells and released biologically active dexamethasone over a sustained period.Conclusion: This oxSWNHs-immobilized system can be used to modify the surface of Ti in implants and be loaded with drugs that stimulate osteogenesis and bone regeneration. Keywords: drug carrier, drug delivery, carbon nanomaterial, carbon nanohorn, peptide aptamer

Minfang Zhang,1,2 Dhifaf A Jasim,1 Cécilia Ménard-Moyon,3 Antonio Nunes,1 Sumio Iijima,2 Alberto Bianco,3 Masako Yudasaka,2 Kostas Kostarelos1 1Nanomedicine Laboratory, Faculty of Medical and Human Sciences and National Graphene Institute, University of Manchester, Manchester, United Kingdom; 2Institute of Advanced Science and Industrial Technology (AIST), Tsukuba, Ibaraki, Japan; 3CNRS, Institute of Molecular and Cellular Biology, Laboratory of Immunopathology and Therapeutic Chemistry, Strasbourg, France Abstract: In this work, we report that the biodistribution and excretion of carbon nanohorns (CNHs) in mice are dependent on their size and functionalization. Small-sized CNHs (30–50 nm; S-CNHs) and large-sized CNHs (80–100 nm; L-CNHs) were chemically functionalized and radiolabeled with [111In]-diethylenetriaminepentaacetic acid and intravenously injected into mice. Their tissue distribution profiles at different time points were determined by single photon emission computed tomography/computed tomography. The results showed that the S-CNHs circulated longer in blood, while the L-CNHs accumulated faster in major organs like the liver and spleen. Small amounts of S-CNHs- and L-CNHs were excreted in urine within the first few hours postinjection, followed by excretion of smaller quantities within the next 48 hours in both urine and feces. The kinetics of excretion for S-CNHs were more rapid than for L-CNHs. Both S-CNH and L-CNH material accumulated mainly in the liver and spleen; however, S-CNH accumulation in the spleen was more prominent than in the liver. Keywords: biodistribution, excretion, functionalization, nano-carbon, nanomedicine

Sachiko Matsumura,1 Ryota Yuge,2 Shigeo Sato,3 Akihiro Tomida,3 Toshinari Ichihashi,2 Hiroshi Irie,4 Sumio Iijima,2,5,6 Kiyotaka Shiba,1 Masako Yudasaka6 1Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan; 2Smart Energy Research Laboratories, NEC Corporation, Tsukuba, Japan; 3Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Koto-ku, Tokyo, Japan; 4Teikyo University School of Medicine, Tokyo, Japan; 5Faculty of Science and Technology, Meijo University, Tenpaku, Nagoya, Japan; 6Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, Higashi, Tsukuba, Japan Abstract: Nanocarbons have many potential medical applications. Drug delivery, diagnostic imaging, and photohyperthermia therapy, especially in the treatment of tumors, have attracted interest. For the further advancement of these application studies, the microscopic localization of nanocarbons in tumor tissues and cells is a prerequisite. In this study, carbon nanohorns (CNHs) with sizes of about 100 nm were intravenously injected into mice having subcutaneously transplanted tumors, and the CNHs in tumor tissue were observed with optical and electron microscopy. In the tumor tissue, the CNHs were found in macrophages and endothelial cells within the blood vessels. Few CNHs were found in tumor cells or in the region away from blood vessels, suggesting that, under these study conditions, the enhanced permeability of tumor blood vessels was not effective for the movement of CNHs through the vessel walls. The CNHs in normal skin tissue were similarly observed. The extravasation of CNHs was not so obvious in tumor but was easily found in normal skin, which was probably due to their vessel wall structure difference. Proper understanding of the location of CNHs in tissues is helpful in the development of the medical uses of CNHs. Keywords: ultrastructural localization, carbon nanohorn, tumor, in vivo, extravasation

The bending of multiwalled carbon nanotubes (MWNTs) over obstacles in the form of gold lines of thickness of a few tens of nanometers on Si substrates is investigated using atomic force microscope (AFM). The condition for suspending carbon nanotubes (CNTs) from two adjacent electrodes above the substrate that is important in nanotechnology is studied.

A study of carbon particle growth synthesized by 20-ms CO (sub)2 laser-pulse irradiation onto a graphite target in Ar gas atmosphere is presented. A constricted structure of carbon cluster emission images has been examined.

Research was conducted to examine the mechanism of the effect of NiCo, Ni and Co catalysts on the yield of single-wall carbon nanotubes (SWNTs) formed by pulsed Nd:YAG laser ablation. In the model of the SWNT formation using a C(sub x)Ni(sub y)Co(sub y) target, graphite absorbs the laser-beam, heats up to 3000-4000 K and transforms into molten C. The formation model also explains how the SWNT growth is influenced by the ambient temperature.

The formation of single-wall carbon nanotubes (SWNTs) using CO2 laser ablation and Nd:YAG laser ablation are studied. Results show that the total irradiation energies were 2 kW/sq cm and 2.4 kW/sq cm for CO2 laser ablation and Nd:YAG laser ablation, respectively. The lowest temperatures at which SWNTs can be formed were 300 K by for CO2 laser ablation and 1170 K for Nd:YAG laser ablation. The lowest pressures for SWNT formation were 50 Torr and 200 Torr for CO2 laser ablation and Nd:YAG laser ablation, respectively.

Research was conducted to examine the structures of carbonaceous deposits derived through laser ablations using targets composed of C, Ni, and Co under different Ar gas pressures. The objective is to elucidate the mechanism of the single-wall carbon nanotube formation by laser ablation. An investigation of the pressure dependence of the target's surface structure and morphology was also carried out.

The changes of the electronic states of single-wall carbon nanotubes (SWNTs) that are treated with various aqueous solutions of electrolytes are investigated. It concluded that the optical spectra of SWNTs were significantly affected when SWNTs that had opened holes or removed caps, were treated through immersion in an aqueous solution of electrolytes, followed by drying at room temperature.

Fluorescence-spectrum measurements are used to investigate the effects of light-assisted oxidation with H2O2 (LAOx) on single-wall carbon nanotubes (SWNTs) that are individually dispersed in an aqueous solution of surfactant. The results have shown that the effect of LAOx depended on the SWNT diameters and the quenching of SWNT fluorescence became irreversible as a result of LAOx, indicating that SWNTs were burnt out.

A study on isolating small aggregates of single-wall carbon nanohorns (SWNHs) by dispersing SWNHs in a D2O solution of sodium dodecylbenzene sulfonate (NaDDBS) and applied ultrasonic and ultra centrifuging is presented. The study reveals that the NaDDBS surfactant isolates SWNH aggregates and the isolated aggregates float within the upper layer of NaDDBS/D2O.

The experimental results of the coalescence of SWNTs that occurred at lower temperature assisted by oxidation are studied. The nitric acid treatment of HiPco SWNTs has revealed two important facts related to controlling the diameter of SWNTs.

Presents a study which examined highly conductive thin films of a charge-transfer complex, hepta-(tetrathiafulvalene) pentaiodide formed by double-source evaporation of tetrathiafulvalene and iodine in vacuum. Effect of the orientation of the crystallites by supply rate of iodine; Description of the experiment; Results of the study.

The physical adsorption of hydrogen on the single-wall carbon nanohorn (SWNH) is shown by the gravimetric experiments, which are the most reliable measurement method for determination of the absorbed quantity of supercritical gas. All single-wall carbon nanotubes (SWNTs) are low purity and contain catalyst metal, SWNHs, being a new material of SWNT family, is very pure and hence the mass production is possible.

The supercritical gas absorption isotherms are classified into Henry-type isotherms, virial isotherms and cooperative isotherms based on an increase in fluid-fluid interaction. This classification is associated with the equation of state (EOS) for a confined fluid in the interaction potential fields of micropores.

The field emission properties of thick films of carbon nanohorns are reported. The films show good field emission characteristics, a low turn-on field and good long-term stability due to the sharp horn-like structures.

The time-resolved imaging and spectroscopic techniques are applied, based on the measurement of emission from the laser plume and light scattering (LS) of the growing materials, to study Nd:YAG laser ablation of a graphite-Co/Ni target and growth of single-walled carbon nanotubes (SWNTs) in an Ar atmosphere at 1200 degree Celsius. The ejection of carbon and metal species and their interaction with ambient Ar atoms to form clusters and particles are characterized.