Effect of surface functionalizations of multi-walled carbon nanotubes on neoplastic transformation potential in primary human lung epithelial cells

Abstract

Functionalized multi-walled carbon nanotube (fMWCNT) development has been intensified to improve their surface activity for numerous applications, and potentially reduce toxic effects. Although MWCNT exposures are associated with lung tumorigenesis in vivo, adverse responses associated with exposure to different fMWCNTs in human lung epithelium are presently unknown. This study hypothesized that different plasma-coating functional groups determine MWCNT neoplastic transformation potential. Using our established model, human primary small airway epithelial cells (pSAECs) were continuously exposed for 8 and 12 weeks at 0.06 μg/cm² to three-month aged as-prepared-(pMWCNT), carboxylated-(MW-COOH), and aminated-MWCNTs (MW-NH_x). Ultrafine carbon black (UFCB) and crocidolite asbestos (ASB) served as particle controls. fMWCNTs were characterized during storage, and exposed cells were assessed for several established cancer cell hallmarks. Characterization analyses conducted at 0 and 2 months of aging detected a loss of surface functional groups over time due to atmospheric oxidation, with MW-NH_x possessing less oxygen and greater lung surfactant binding affinity. Following 8 weeks of exposure, all fMWCNT-exposed cells exhibited significant increased proliferation compared to controls at 7 d post-treatment, while UFCB- and ASB-exposed cells did not differ significantly from controls. UFCB, pMWCNT, and MW-COOH exposure stimulated significant transient invasion behavior. Conversely, aged MW-NH_x-exposed cells displayed moderate increases in soft agar colony formation and morphological transformation potential, while UFCB cells showed a minimal effect compared to all other treatments. In summary, surface properties of aged fMWCNTs can impact cell transformation events in vitro following continuous, occupationally relevant exposures.

Keywords:

• Surface properties
• aging effects
• functionalization
• multi-walled carbon nanotubes
• cell transformation

Acknowledgements

We kindly thank Dr. Afshin Tarat and Perpetuus Carbon Technologies for independent validation of MWCNT characterization. Vamsi Kodali kindly assisted with DTT surface reactivity determination.

Disclosure statement

The findings and conclusions in this article are those of the authors and do not necessarily represent the view of the National Institute for Occupational Safety and Health.

Additional information

Funding

This study was supported by funds from the National Institute for Occupational Safety and Health/Nanotechnology Research Center, National Institutes of Health [R01-ES022968 and R01-EB018857], and National Science Foundation [CBET-1434503].