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

Our plain-English summary of Effect of dispersants of multi-walled carbon nanotubes on cellular uptake and biological responses, by H. Haniu, N. Saito, Y. Matsuda, et al (International Journal of Nanomedicine, 2011).

The study

• Authors: H. Haniu, N. Saito, Y. Matsuda, Y.A. Kim, K.C. Park, T. Tsukahara, Y. Usui, K. Aoki, M. Shimizu, N. Ogihara, K. Hara, S. Takanashi, M. Okamoto, N. Ishigaki, K. Nakamura, H. Kato
• Journal: International Journal of Nanomedicine
• Published: 2011;6:3295-307
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

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(®), Shōwa Denkō 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.

In plain English

This laboratory study used cells grown in dishes, not asbestos, people or animals. The authors exposed human airway cells (BEAS-2B) to vapor grown carbon fiber (VGCF), a commercial multi-walled carbon nanotube. The fibers were suspended in gelatin, carboxylmethyl cellulose (CMC) or DPPC. At 10 µg/mL for 24 hours, the results section reported that VGCF in gelatin cut viability by 38% and VGCF in DPPC by 83%, while VGCF in CMC gave 114% of control. The discussion, however, described viability as less than 50% with gelatin and about 80% with DPPC. Uptake was much higher with gelatin and DPPC than with CMC, which barely rose; the authors read this as fibers in CMC not entering cells. Only cells exposed to VGCF in gelatin or DPPC released more of the inflammation signals IL-6 and IL-8. Using fibers suspended in gelatin, viability fell as the dose rose both in BEAS-2B cells and in a human malignant pleural mesothelioma cell line (MESO-1). The authors concluded that the dispersant influences the response and that toxicity followed the amount of fiber inside cells.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) cell culture experiment
• Who was studied: Two commercially obtained human cell lines: BEAS-2B bronchial epithelial cells and MESO-1 malignant pleural mesothelioma cells. No people or animals were studied.
• Exposure: Vapor grown carbon fiber (VGCF), a commercial multi-walled carbon nanotube material, not asbestos. The company reported a mean diameter of 150 nm and a mean length of 8 µm. The fibers were suspended in gelatin, carboxylmethyl cellulose (CMC) or DPPC. Cells were mainly exposed to 10 µg/mL for 24 hours. Dose-response tests used VGCF in gelatin at 0.3125 to 40 µg/mL.
• Main results:
  • The results section reported that, in BEAS-2B cells exposed to 10 µg/mL VGCF for 24 hours, VGCF in gelatin decreased viability by 38% and VGCF in DPPC decreased viability by 83%. The discussion gives different descriptions of both (see text problems).
  • The discussion described viability with VGCF in gelatin as decreased to less than 50%.
  • In BEAS-2B cells, VGCF in CMC increased viability compared with the control (114%).
  • After 1 hour, the light-scattering measure of uptake in BEAS-2B cells was significantly increased in all three dispersants compared with the dispersant-only control. Relative to control, it was 1.65 in gelatin and less than 1.1 in CMC or DPPC.
  • After 24 hours, the uptake ratio in BEAS-2B cells was 2.40 for gelatin, 1.88 for DPPC and 1.05 for CMC. The authors interpreted this as VGCF in CMC not being taken into the cells.
  • BEAS-2B cells exposed to VGCF in gelatin or DPPC secreted significantly more IL-6 and IL-8. Cells exposed to VGCF in CMC showed no increase.
  • TNF-α and IL-1β were not detected under any condition.
  • With VGCF in gelatin, the concentration that reduced viability by half (IC50) was 7 µg/mL in BEAS-2B cells and 17 µg/mL in MESO-1 cells.
  • At each cell line's IC50, the relative uptake ratio was about 2.1 in both BEAS-2B and MESO-1 cells.
• The authors' conclusion: The authors concluded that the cells' response to VGCF in the dish is influenced by the dispersant. They also concluded that VGCF caused cytotoxicity and inflammatory reactions according to how much fiber was inside the cells, not according to differences between cell types.
• Limitations the authors state:
  • The authors stated that more detailed studies are needed to explain the biological mechanisms.
  • The authors did not examine whether the dispersant affects how cells recognize or take up the nanotubes.

Topics

Medical terms in this study, explained in our Lexicon: Cytokine, Pleural Mesothelioma.

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