Carbon nanotubes (CNT) are well-ordered, high aspect ratio allotropes of carbon. The two main variants, namely single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) both possess the characteristics of high tensile strength, ultra-light weight, and excellent chemical and thermal stability. They also possess the semi- and metallic-conductive properties. This startling array of features has led to many proposed applications in the biomedical field. However, it is only recently that information on toxicity and biocompatibility has become available. Herein is presented a review on the toxicity and biocompatibility of carbon nanotubes.
Animals ; Biocompatible Materials ; toxicity ; Humans ; Materials Testing ; Nanotubes, Carbon ; toxicity ; Toxicity Tests

OBJECTIVE: To investigate the effects of multi-walled carbon nanotubes (MWCNTs) with different length or chemical modification on endothelial cell activation and to explore the role of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome. METHODS: MWCNTs were characterized by dynamic light scattering (DLS) after being suspended in culture medium. The immortalized mouse cerebral microvascular endothelial cell line b.End3 was treated with short MWCNTs (S-MWCNT, 0.5 to 2 μm), long MWCNTs (L-MWCNT, 10 to 30 μm) and the above long MWCNTs functionalized by carboxyl-(L-MWCNT-COOH), amino-(L-MWCNT-NH₂) or hydroxyl-(L-MWCNT-OH) modification. Cytotoxicity of MWCNTs in b.End3 cells was determined by cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release assay, and non-toxic low dose was selected for subsequent experiments. Effects of all types of MWCNTs on the endothelial activation of b.End3 were determined by the measurement of vascular cell adhesion molecule-1 (VCAM-1) concentration in cell supernatant and adhesion assay of human monocytic cell line THP-1 to b.End3.To further elucidate the mechanism involved, the protein expressions of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3(NLRP3) in cells treated with S-MWCNT, L-MWCNT and L-MWCNT-COOH were measured by Western blot. RESULTS: At a higher concentration (125 μg/cm²) and treated for 24 h, all types of MWCNTs significantly inhibited viability of b.End3 cells. At a sub-toxic concentration (6.25 μg/cm²), all types of MWCNTs treated for 12 h significantly induced the activation of b.End3 cells, as evidenced by the elevated VCAM-1 release and THP-1 adhesion. Compared with S-MWCNT, L-MWCNT significantly promoted endothelial cell activation. L-MWCNT and L-MWCNT-COOH activated b.End3 cells to a similar extent. Furthermore, treatment with S-MWCNT, L-MWCNT and L-MWCNT-COOH increased NLRP3 expression in a time-dependent manner at 6.25 μg/cm². Compared with S-MWCNT, cells treated with L-MWCNT for 4 h and 12 h exhibited significantly increased protein expressions of NLRP3. However, no significant differences were detected in the level of NLRP3 protein in cells treated with L-MWCNT and L-MWCNT-COOH. CONCLUSION Compared with the surface chemical modification, length changes of MWCNTs exerted more influence on endothelial cell activation, which may be related to the activation of NLRP3 inflammasome. Our study contributes further understanding of the impact of MWCNTs on endothelial cells, which may have implications for the improvement of safety evaluation of MWCNTs.
Cell Line ; Cell Survival ; Endothelial Cells ; Nanotubes, Carbon/toxicity* ; Vascular Cell Adhesion Molecule-1

OBJECTIVES: Carbon nanotubes are an important new class of technological materials that have numerous novel and useful properties. Multi-walled carbon nanotubes (MWCNTs), which is a nanomaterial, is now in mass production because of its excellent mechanical and electrical properties. Although MWCNTs appear to have great industrial and medical potential, there is little information regarding their toxicological effects on researchers and workers who could be exposed to them by inhalation during the handling of MWCNTs. METHODS: The generation of an untangled MWCNT aerosol with a consistent concentration without using surfactants that was designed to be tested in in vivo inhalation toxicity testing was attempted. To do this, MWCNTs were dispersed in deionized water without the addition of any surfactant. To facilitate the dispersion of MWCNTs in deionized water, the water was heated to 40degrees C, 60degrees C, and 80degrees C depending on the sample with ultrasonic sonication. Then the dispersed MWCNTs were atomized to generate the MWCNT aerosol. After aerosolization of the MWCNTs, the shapes of the NTs were examined by transmission electron microscopy. RESULTS: The aerosolized MWCNTs exhibited an untangled shape and the MWCNT generation rate was about 50 mg/m3. CONCLUSION: Our method provided sufficient concentration and dispersion of MWNCTs to be used for inhalation toxicity testing.
Carbon ; Electrons ; Handling (Psychology) ; Hot Temperature ; Inhalation ; Nanostructures ; Nanotubes, Carbon ; Sonication ; Surface-Active Agents ; Toxicity Tests ; Ultrasonics ; Water

A substantial literature demonstrates that the main ultrafine particles found in ambient urban air are combustion-derived nanoparticles (CDNP) which originate from a number of sources and pose a hazard to the lungs. For CDNP, three properties appear important-surface area, organics and metals. All of these can generate free radicals and so induce oxidative stress and inflammation. Inflammation is a process involved in the diseases exhibited by the individuals susceptible to the effects of PM- development and exacerbations of airways disease and cardiovascular disease. It is therefore possible to implicate CDNP in the common adverse effects of increased PM. The adverse effects of increases in PM on the cardiovascular system are well-documented in the epidemiological literature and, as argued above, these effects are likely to be driven by the combustion-derived NP. The epidemiological findings can be explained in a number of hypotheses regarding the action of NP:-1) Inflammation in the lungs caused by NP causes atheromatous plaque development and destabilization; 2) The inflammation in the lungs causes alteration in the clotting status or fibrinolytic balance favouring thrombogenesis; 3) The NP themselves or metals/organics released by the particles enter the circulation and have direct effects on the endothelium, plaques, the clotting system or the autonomic nervous system/ heart rhythm. Environmental nanoparticles are accidentally produced but they provide a toxicological model for a new class of purposely 'engineered' NP arising from the nanotechnology industry, whose effects are much less understood. Bridging our toxicological knowledge between the environmental nanoparticles and the new engineered nanoparticles is a considerable challenge.
Air Pollutants/*toxicity ; Carcinogens, Environmental/*toxicity ; Cardiovascular Diseases/etiology ; Endothelium/drug effects ; Humans ; Lung/*drug effects ; Nanoparticles/*toxicity ; Nanotubes, Carbon/toxicity ; Particle Size ; Quantitative Structure-Activity Relationship

OBJECTIVEThis study was aimed to investigate the toxic effects of 3 nanomaterials, i.e. multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO), and reduced graphene oxide (RGO), on zebrafish embryos.

METHODSThe 2-h post-fertilization (hpf) zebrafish embryos were exposed to MWCNTs, GO, and RGO at different concentrations (1, 5, 10, 50, 100 mg/L) for 96 h. Afterwards, the effects of the 3 nanomateria on spontaneous movement, heart rate, hatching rate, length of larvae, mortality, and malformations ls were evaluated.

RESULTSStatistical analysis indicated that RGO significantly inhibited the hatching of zebrafish embryos. Furthermore, RGO and MWCNTs decreased the length of the hatched larvae at 96 hpf. No obvious morphological malformation or mortality was observed in the zebrafish embryos after exposure to the three nanomaterials.

CONCLUSIONMWCNTs, GO, and RGO were all toxic to zebrafish embryos to influence embryos hatching and larvae length. Although no obvious morphological malformation and mortality were observed in exposed zebrafish embryos, further studies on the toxicity of the three nanomaterials are still needed.

Animals ; Embryo, Nonmammalian ; Embryonic Development ; drug effects ; Female ; Graphite ; toxicity ; Heart Rate ; drug effects ; Male ; Movement ; drug effects ; Nanotubes, Carbon ; toxicity ; Oxides ; toxicity ; Toxicity Tests ; Zebrafish

OBJECTIVETo investigate the cytotoxic effect of multi-walled carbon nanotubes (MWCNTs) on human liver L02 cells and its relevant mechanism.

METHODSMWCNTs, carboxyl modification MWCNTs (MWCNTs-COOH), and hydroxyl modification MWCNTs (MWCNTs-OH) were characterized by transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The carbon nanotubes at concentrations of 12.5, 25, 50, 100, and 200 μg/ml were incubated with human liver L02 cells for 24, 48 and 72 hours, respectively. The cell viability was evaluated by water soluble tetrazolium salts assay and the intercellular reactive oxygen species induced by the carbon nanotubes were detected by 2', 7'-dichlorodihydrofluorescein diacetate method.

RESULTSTransmission electron microscope showed that the average outside diameters (10 to 20 nm) and the average length (10 to 30 μm) of the three MWCNTs were similar. Scanning electron microscope indicated that the three MWCNTs had a similar surface topography. X-ray photoelectron spectroscopy demonstrated that the MWCNTs-COOH and MWCNTs-OH had relatively high peak areas at 289 and 286ev, respectively,indicating that they have been modified by carboxyl and hydroxyl groups,respectively. Water soluble tetrazolium salts assay showed that the MWCNTs-COOH was less cytotoxic when compared to MWCNTs which demonstrated to be slightly more cytotoxic than MWCNTs-OH. The capability to induce increase in intracellular reactive oxygen species was in the following order: MWCNTs > MWCNTs-COOH > MWCNTs-OH.

CONCLUSIONSModification of MWCNTs with carboxyl group and hydroxyl group improves the biocompatibility of MWCNTs to some extents. MWCNTs-COOH has better compatibility than MWCNTs at the low concentration,and MWCNTs-OH showed better compatibility than MWCNTs after 48 hours. Different mechanisms may be involved in the interaction between cells and the MWCNTs with different chemical surfaces.

Cell Survival ; drug effects ; Cells, Cultured ; Hepatocytes ; drug effects ; metabolism ; Humans ; Nanotubes, Carbon ; chemistry ; toxicity ; Reactive Oxygen Species ; metabolism

OBJECTIVETo observe the pulmonary toxicity of multi-walled carbon nanotubes (MWCNTs) in high-fat diet SD rats.

METHODSOne hundred forty male SD rats were randomly divided into 6 groups. The normal control group, high-fat diet model group, vehicle group, and group treated with low dose of MWCNTs consisted of 30 rats, respectively, which were divided in 3 subgroups (10 rats each subgroup), respectively. The groups treated with medium and high loses of MWCNTs consisted of 10 rats, respectively. All the animals were exposed to high-fat-diet except for the control group which was given with normal diet. Before intravenous exposure, the high-fat diet model group, vehicle group, and three MWCNTs treated groups were gavaged with 700 thousand U/kg Vit D3 for three days, then given with high-fat-diet. The vehicle group was exposed to normal saline containing 1% Tween 80 and the low exposure group was exposed to MWCNTs at the dose of 50 µg/kg by tail vein injection twice a week for 8, 12 or 16 weeks. Other tow exposure groups were exposed to MWCNTs at the doses of 100, and 200 µg/kg by tail vein injection twice a week, respectively for 16 weeks. The lungs were from the executed rats, the lung indexes were calculated, the pathological changes of lungs were examined under light microscope after HE staining. qRT-PCR assay was utilized to detect the expression levels of pro-inflammation cytokines IL-1β (IL-1β) and TNF-α mRNA in the lungs.

RESULTSAs compared with the vehicle group, the lung indexes in groups exposed to 100 and 200 µg/kg MWCNTs increased significantly (P < 0.05). It was found under light microscope that the MWCNTs were accumulated in lungs of three exposure groups in 16 weeks after exposure, including pneumorrhagia, alveolar walls thicken, fibrosis, and granulomas. As compared with the vehicle group, the levels of IL-1β mRNA in group exposed to 50 µg/kg MWCNTs for 12 weeks and the groups exposed to 50, 100 and 200 µg/kg MWCNTs for 16 weeks decreased significantly (P < 0.05). As compared with the vehicle group, the levels of TNF-α mRNA in the groups exposed to 50 µg/kg MWCNTs for 8 and 16 weeks increased significantly (P < 0.05), the level of TNF-α mRNA in the groups exposed to 50 µg/kg MWCNTs for 12 weeks decreased significantly (P < 0.05). As compared with the vehicle group, the level of TNF-α mRNA in the groups exposed to 200 µg/kg MWCNTs for 16 weeks reduced significantly (P < 0.05).

CONCLUSIONThe MWCNTs accumulation and chronic inflammatory changes were found in the lungs of rats exposed to MWCNTs by tail vein injection.

Animals ; Cytokines ; analysis ; Diet, High-Fat ; Injections, Intravenous ; Lung ; drug effects ; pathology ; Male ; Nanotubes, Carbon ; toxicity ; Rats ; Rats, Sprague-Dawley

We examined the biocompatibility and the safety of a-calcium sulfate hemihydrate (CSH)/multi-walled carbon nanotube (MWCNT) composites for bone reconstruction application. The biocompatibility of the CSH/MWCNT composites was evaluated by the measures which taking L929 fibroblast cells cultured in the extracted liquid of the composite soaking solution and putting bone marrow stromal cells planted on the composite pellets in vitro, respectively. The cell proliferation was evaluated by MTT test and further observed using an inverted optical microscope and a scanning electric microscope. The toxicity of the composites was evaluated by acute and subacute systemic toxicity test. Long-term muscle and bone implantation in vivo tests were also conducted. L929 fibroblast cells grew well in the extracted liquid, as well as bone marrow stromal cells that could adhere on the surface of sample pellets and proliferated rapidly. MTT test showed that there were no significant differences between the experimental and control groups (P > 0.05). In vivo test manifested that the composites were no toxicity, no irritation to skin and good for bone defect reconstruction. It was proved that a-calcium sulfate hemihydrate (CSH)/multi-walled carbon nanotube (MWCNT) composites exhibited excellent biocompatibility for the potential application in bone tissue engineering.
Animals ; Biocompatible Materials ; chemistry ; Bone Marrow Cells ; cytology ; Bone Substitutes ; chemical synthesis ; chemistry ; Calcium Sulfate ; chemistry ; Cell Line ; Cell Proliferation ; Fibroblasts ; cytology ; Materials Testing ; Nanotubes, Carbon ; chemistry ; Rabbits ; Stromal Cells ; cytology ; Tissue Engineering ; methods ; Toxicity Tests

OBJECTIVETo investigate in vitro cytotoxicity and oxidative stress response induced by multiwalled carbon nanotubes (MWCNTs).

METHODSCultured macrophages (murine RAW264.7 cells) and alveolar epithelium cells type II (human A549 lung cells) were exposed to the blank control, DNA salt control, and the MWCNTs suspensions at 2.5, 10, 25, and 100 μg/mL for 24 h. Each treatment was evaluated by cell viability, cytotoxicity and oxidative stress.

RESULTSOverall, both cell lines had similar patterns in response to the cytotoxicity and oxidative stress of MWCNTs. DNA salt treatment showed no change compared to the blank control. In both cell lines, significant changes at the doses of 25 and 100 μg/mL treatments were found in cell viabilities, cytotoxicity, and oxidative stress indexes. The reactive oxygen species (ROS) generation was also found to be significantly higher at the dose of 10 μg/mL treatment, whereas no change was seen in most of the indexes. The ROS generation in both cell lines went up in minutes, reached the climax within an hour and faded down after several hours.

CONCLUSIONExposure to MWCNTs resulted in a dose-dependent cytotoxicity in cultured RAW264.7 cells and A549 cells, that was closely correlated to the increased oxidative stress.

Animals ; Cell Culture Techniques ; Cell Line ; Cell Survival ; drug effects ; Dose-Response Relationship, Drug ; Humans ; Lung ; drug effects ; enzymology ; metabolism ; pathology ; Macrophages, Alveolar ; drug effects ; enzymology ; metabolism ; pathology ; Mice ; Microscopy, Electron, Scanning ; Microscopy, Electron, Transmission ; Microscopy, Fluorescence ; Nanotubes, Carbon ; chemistry ; toxicity ; Oxidative Stress ; drug effects ; Reactive Oxygen Species ; metabolism ; Surface Properties