Abstract 5464: Genotoxicity of multi-walled carbon nanotubes at occupationally relevant doses

Particle and Fibre Toxicology (Impact Factor: 6.99). 01/2014; 11(1):6. DOI: 10.1186/1743-8977-11-6
Source: PubMed

ABSTRACT Carbon nanotubes are commercially-important products of nanotechnology; however, their low density and small size makes carbon nanotube respiratory exposures likely during their production or processing. We have previously shown mitotic spindle aberrations in cultured primary and immortalized human airway epithelial cells exposed to single-walled carbon nanotubes (SWCNT). In this study, we examined whether multi-walled carbon nanotubes (MWCNT) cause mitotic spindle damage in cultured cells at doses equivalent to 34 years of exposure at the NIOSH Recommended Exposure Limit (REL). MWCNT induced a dose responsive increase in disrupted centrosomes, abnormal mitotic spindles and aneuploid chromosome number 24 hours after exposure to 0.024, 0.24, 2.4 and 24 mug/cm2 MWCNT. Monopolar mitotic spindles comprised 95% of disrupted mitoses. Three-dimensional reconstructions of 0.1 mum optical sections showed carbon nanotubes integrated with microtubules, DNA and within the centrosome structure. Cell cycle analysis demonstrated a greater number of cells in S-phase and fewer cells in the G2 phase in MWCNT-treated compared to diluent control, indicating a G1/S block in the cell cycle. The monopolar phenotype of the disrupted mitotic spindles and the G1/S block in the cell cycle is in sharp contrast to the multi-polar spindle and G2 block in the cell cycle previously observed following exposure to SWCNT. One month following exposure to MWCNT there was a dramatic increase in both size and number of colonies compared to diluent control cultures, indicating a potential to pass the genetic damage to daughter cells. Our results demonstrate significant disruption of the mitotic spindle by MWCNT at occupationally relevant exposure levels.

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    ABSTRACT: Background Biological effects of tailor-made multi-walled carbon nanotubes (MWCNTs) without functionalization were investigated in vivo in a two-year carcinogenicity study. In the past, intraperitoneal carcinogenicity studies in rats using biopersistent granular dusts had always been negative, whereas a number of such studies with different asbestos fibers had shown tumor induction. The aim of this study was to identify possible carcinogenic effects of MWCNTs. We compared induced tumors with asbestos-induced mesotheliomas and evaluated their relevance for humans by immunohistochemical methods.MethodsA total of 500 male Wistar rats (50 per group) were treated once by intraperitoneal injection with 109 or 5¿×¿109 WHO carbon nanotubes of one of four different MWCNTs suspended in artificial lung medium, which was also used as negative control. Amosite asbestos (108 WHO fibers) served as positive control. Morbid rats were sacrificed and necropsy comprising all organs was performed. Histopathological classification of tumors and, additionally, immunohistochemistry were conducted for podoplanin, pan-cytokeratin, and vimentin to compare induced tumors with malignant mesotheliomas occurring in humans.ResultsTreatments induced tumors in all dose groups, but incidences and times to tumor differed between groups. Most tumors were histologically and immunohistochemically classified as malignant mesotheliomas, revealing a predominantly superficial spread on the serosal surface of the abdominal cavity. Furthermore, most tumors showed invasion of peritoneal organs, especially the diaphragm. All tested MWCNT types caused mesotheliomas. We observed highest frequencies and earliest appearances after treatment with the rather straight MWCNT types A and B. In the MWCNT C groups, first appearances of morbid mesothelioma-bearing rats were only slightly later. Later during the two-year study, we found mesotheliomas also in rats treated with MWCNT D ¿ the most curved type of nanotubes. Malignant mesotheliomas induced by intraperitoneal injection of different MWCNTs and of asbestos were histopathologically and immunohistochemically similar, also compared with mesotheliomas in man, suggesting similar pathogenesis.Conclusion We showed a carcinogenic effect for all tested MWCNTs. Besides aspect ratio, curvature seems to be an important parameter influencing the carcinogenicity of MWCNTs.
    Particle and Fibre Toxicology 11/2014; 11(1):59. DOI:10.1186/s12989-014-0059-z · 6.99 Impact Factor
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    ABSTRACT: Chitosan/gold nanocomposite was synthesized using the chemical reduction method. The XRD pattern shows the semi-crystalline nature of chitosan and the face centered cubic structure of gold. The binding of gold to chitosan was confirmed using XPS and FTIR. The presence of gold in its metallic state is evident from XPS. The prepared nanocomposite was used as a drug delivery carrier for 5-fluorouracil. The encapsulation efficiency of 5-FU and the drug loading efficiency were found to be 96% and 41% respectively. A dialysis membrane was used to study the release of 5-fluorouracil from chitosan/gold nanocomposite. The amount of drug released in vitro was analyzed using the UV-vis characterization of PBS solution. 5-fluorouracil encapsulated nanocomposite was characterized using HRTEM with SAED, HRSEM with elemental mapping, XRD and FTIR analysis. The presence of fluorine, observed from the elemental mapping, confirms the loading of the drug into the nanocomposite. Cytotoxicity analysis was performed for the MCF-7 and VERO cell lines, which shows the effectiveness of the sample towards the destruction of MCF-7 and its non-toxicity towards VERO. 50% cell viability for the MCF-7 cells was obtained at a sample concentration of 31.2 mg ml�1. The non-toxicity of the system towards VERO cells at the concentration wherein IC50 is obtained for MCF-7 and the adherence of the maximum portion of the release profile to zero order kinetics, which means a constant release of the drug from the delivery vehicle, are the highlights of this system.
    RSC Advances 01/2015; 05(2):1024 - 1032. DOI:10.1039/c4ra11615a · 3.71 Impact Factor
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    ABSTRACT: There is a current interest in reducing the in vivo toxicity testing of nanomaterials in animals by increasing toxicity testing using in vitro cellular assays; however, toxicological results are seldom concordant between in vivo and in vitro models. This study compared global multi-walled carbon nanotube (MWCNT)-induced gene expression from human lung epithelial and microvascular endothelial cells in monoculture and coculture with gene expression from mouse lungs exposed to MWCNT. Using a cutoff of 10% false discovery rate and 1.5 fold change, we determined that there were more concordant genes (gene expression both up- or downregulated in vivo and in vitro) expressed in both cell types in coculture than in monoculture. When reduced to only those genes involved in inflammation and fibrosis, known outcomes of in vivo MWCNT exposure, there were more disease-related concordant genes expressed in coculture than monoculture. Additionally, different cellular signaling pathways are activated in response to MWCNT dependent upon culturing conditions. As coculture gene expression better correlated with in vivo gene expression, we suggest that cellular cocultures may offer enhanced in vitro models for nanoparticle risk assessment and the reduction of in vivo toxicological testing. Copyright © 2014. Published by Elsevier Ireland Ltd.
    Toxicology 12/2014; 328. DOI:10.1016/j.tox.2014.12.012 · 3.75 Impact Factor

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