title: In vitro chromosomal aberrations induced by various shapes of multi-walled carbon nanotubes (MWCNTs).
abstract: OBJECTIVE
  IARC has classified one type of multi-walled carbon nanotubes (MWCNTs), MWNT-7, as possibly carcinogenic to humans (Group 2B); however, other types of MWCNT were categorized as not classifiable as to their carcinogenicity to humans (Group 3). In vitro chromosomal aberration assays of MWNT-7 showed polyploid formation but not structural abnormalities. This study investigated the influence of the shape and size of MWCNT on in vitro induction of chromosomal aberrations.
  
  
  METHODS
  Microscopic analysis and viable cell counting were used to assay for chromosomal aberrations and cytotoxicity induced in a Chinese hamster lung cell line (CHL/IU) exposed to different MWCNTs.
  
  
  RESULTS
  Using scanning electron microscopy, seven MWCNTs were classified into three types: straight fibrous, curved fibrous, and tangled. The straight fibrous MWCNTs were the strongest inducers of polyploidy and the most cytotoxic among the three types of MWCNTs. The curved fibrous MWCNTs induced more polyploidy than the tangled MWCNTs, and the cytotoxicity of both types seemed to be a reflection of their induction of polyploidy. None of the seven MWCNTs induced structural chromosomal aberrations.
  
  
  CONCLUSIONS
  The non-clastogenicity of the MWCNTs indicates that the MWCNTs may not interact directly with DNA. Since the straight fibrous MWCNTs, which exhibit a structure similar to asbestos, were the strongest inducers of polyploidy, MWCNT shape may be an important factor in induction of polyploidy. We hypothesize that CHL/IU cells endocytosed MWCNTs and formed endosomes with shapes corresponding to those of the endocytosed MWCNTs, and that the long axis diameter of the endosome is important in the capability of MWCNTs to induce polyploidy.
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masumi
authors.initials: M
authors.lastname: Asakura
authors.forename: Chigusa
authors.initials: C
authors.lastname: Ishioka
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
authors.forename: Taku
authors.initials: T
authors.lastname: Katagiri
authors.forename: Shoji
authors.initials: S
authors.lastname: Fukushima
mesh_terms: D000818:Animals; D002460:Cell Line; D002869:Chromosome Aberrations / Q000139:chemically induced*; D006224:Cricetinae; D003412:Cricetulus; D008168:Lung / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D037742:Nanotubes, Carbon / Q000009:adverse effects* / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D037742:Nanotubes, Carbon