Genotoxicity of carbon nanofibers: Are they potentially more or less dangerous than carbon nanotubes or asbestos?

Abstract

The production of carbon nanofibers and nanotubes (CNF/CNT) and their composite products is increasing globally. CNF are generating great interest in industrial sectors such as energy production and electronics, where alternative materials may have limited performance or are produced at a much higher cost. However, despite the increasing industrial use of carbon nanofibers, information on their potential adverse health effects is limited. In the current study, we examine the cytotoxic and genotoxic potential of carbon-based nanofibers (Pyrograf®-III) and compare this material with the effects of asbestos fibers (crocidolite) or single-walled carbon nanotubes (SWCNT). The genotoxic effects in the lung fibroblast (V79) cell line were examined using two complementary assays: the comet assay and micronucleus (MN) test. In addition, we utilized fluorescence in situ hybridization to detect the chromatin pan-centromeric signals within the MN indicating their origin by aneugenic (chromosomal malsegregation) or clastogenic (chromosome breakage) mechanisms. Cytotoxicity tests revealed a concentration- and time-dependent loss of V79 cell viability after exposure to all tested materials in the following sequence: asbestos>CNF>SWCNT. Additionally, cellular uptake and generation of oxygen radicals was seen in the murine RAW264.7 macrophages following exposure to CNF or asbestos but not after administration of SWCNT. DNA damage and MN induction were found after exposure to all tested materials with the strongest effect seen for CNF. Finally, we demonstrated that CNF induced predominately centromere-positive MN in primary human small airway epithelial cells (SAEC) indicating aneugenic events. Further investigations are warranted to elucidate the possible mechanisms involved in CNF-induced genotoxicity.

Occupational Nanosafety Considerations for Carbon Nanotubes and Carbon Nanofibers

“…37,38 Purified CNTs have been reported to generate low levels of reactive species in a cellular system yet remain bioactive in vivo. 16,39 Low doses of SWCNTs, representative of CNT lung burdens and alveolar epithelial cell surface area achieved after aspiration of 40 μg/mouse, exhibit low cytotoxicity. Rather, low dose SWCNT exposure of lung fibroblasts increases proliferation rate and collagen production.…”

“…41,42 Purified SWCNTs do not generate radicals yet cause a measurable level of genotoxicity to fibroblasts in the comet and micronucleus assay. 39 However, CNFs generate significant radicals and are more genotoxic than SWCNTs. 43 Sargent et al 44 reported that SWCNTs disrupt centrosomes in dividing lung epithelial cells resulting in multipolar mitosis and aneuploidy.…”

“…Kisin et al 39 reported that CNFs induced a more potent genotoxic response than SWCNTs in vitro. In contrast, the potency of SWCNTs and MWCNTs to transform lung epithelial cells in a long-term culture system was similar.…”

Citotoxicidade e genotoxicidade de nanotubos de carbon

“…: TGA, EELS e microscopia de alta resolução). 114,118 Entre os vários trabalhos de genotoxicidade publicados 75,85,94,[121][122][123][124] poucos têm feito uso de análises térmicas (um parâmetro importante para caracterização e recomendado pelo National Institute of Standards and Technology). Muitos trabalhos apresentam imagens de microscopia, porém essas são de baixa resolução 74,83,85,87,88,93,97 o que compromete o entendimento dos tipos de contaminantes existentes nos NTCs.…”

Effects of carbon nanofiber on physiology of Drosophila

“…Furthermore, among the few studies that have evaluated CNF toxicity, only in vitro-cultured cell models have been used. 7,10,11 Although nanomaterial-mediated toxicity has been largely attributed to the generation of free radicals, the exact molecular mechanism underlying reactive oxygen species (ROS) generation by nanoparticles remains unclear. [12][13][14] Flies exposed to silver nanoparticles are known to show depleted levels of glutathione (GSH) as well as increased antioxidant enzyme SOD and CAT activities.…”