Effect of dispersants of multi-walled carbon nanotubes on cellular uptake and biological responses

Hisao Haniu¹, Naoto Saito², Yoshikazu Matsuda³, Yoong-Ahm Kim⁴, Ki Chul Park¹, Tamotsu Tsukahara⁵, Yuki Usui⁶, Kaoru Aoki⁷, Masayuki Shimizu⁷, Nobuhide Ogihara⁷, Kazuo Hara⁷, Seiji Takanashi⁷, Masanori Okamoto⁷, Norio Ishigaki⁷, Koichi Nakamura⁷, Hiroyuki Kato^7
1Institute of Carbon Science and Technology, Shinshu University, Matsumoto, Nagano, Japan; ²Department of Applied Physical Therapy, Shinshu University School of Health Sciences, Matsumoto, Nagano, Japan; ³Clinical Pharmacology Educational Center, Nihon Pharmaceutical University, Ina-machi, Saitama, Japan; ⁴Faculty of Engineering, Shinshu University, Nagano-shi, Nagano, Japan; ⁵Department of Integrative Physiology and Bio-System Control, Shinshu University School of Medicine, Matsumoto-shi, Nagano, Japan; ⁶Research Center for Exotic Nanocarbons, Shinshu University, Matsumoto, Nagano, Japan; ⁷Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Nagano, Japan

Abstract: Although there have been many reports about the cytotoxicity of multi-walled carbon nanotubes (MWCNTs), the results are still controversial. To investigate one possible reason, the authors investigated the influence of MWCNT dispersants on cellular uptake and cytotoxicity. Cytotoxicity was examined (measured by alamarBlue^® assay), as well as intracellular MWCNT concentration and cytokine secretion (measured by flow cytometry) in human bronchial epithelial cells (BEAS-2B) exposed to a type of highly purified MWCNT vapor grown carbon fiber (VGCF^®, Showa Denko Kabushiki-gaisha, Tokyo, Japan) in three different dispersants (gelatin, carboxylmethyl cellulose, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine). The authors also researched the relationship between the intracellular concentration of MWCNTs and cytotoxicity by using two cell lines, BEAS-2B and MESO-1 human malignant pleural mesothelioma cells. The intracellular concentration of VGCF was different for each of the three dispersants, and the levels of cytotoxicity and inflammatory response were correlated with the intracellular concentration of VGCF. A relationship between the intracellular concentration of VGCF and cytotoxic effects was observed in both cell lines. The results indicate that dispersants affect VGCF uptake into cells and that cytotoxicity depends on the intracellular concentration of VGCF, not on the exposed dosage. Thus, toxicity appears to depend on exposure time, even at low VGCF concentrations, because VGCF is biopersistent.

Keywords: multi-walled carbon nanotube, cytotoxicity, intracellular concentration, dispersant, cytokine secretion