Biological responses according to the shape and size of carbon nanotubes in BEAS-2B and MESO-1 cells

Our plain-English summary of Biological responses according to the shape and size of carbon nanotubes in BEAS-2B and MESO-1 cells, by H. Haniu, N. Saito, Y. Matsuda, et al (International Journal of Nanomedicine, 2014).

The study

• Authors: H. Haniu, N. Saito, Y. Matsuda, T. Tsukahara, Y. Usui, K. Maruyama, S. Takanashi, K. Aoki, S. Kobayashi, H. Nomura, M. Tanaka, M. Okamoto, H. Kato
• Journal: International Journal of Nanomedicine
• Published: 2014;9:1979-90
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This study aimed to investigate the influence of the shape and size of multi-walled carbon nanotubes (MWCNTs) and cup-stacked carbon nanotubes (CSCNTs) on biological responses in vitro. Three types of MWCNTs - VGCF(®)-X, VGCF(®)-S, and VGCF(®) (vapor grown carbon fibers; with diameters of 15, 80, and 150 nm, respectively) - and three CSCNTs of different lengths (CS-L, 20-80 μm; CS-S, 0.5-20 μm; and CS-M, of intermediate length) were tested. Human bronchial epithelial (BEAS-2B) and malignant pleural mesothelioma cells were exposed to the CNTs (1-50 μg/mL), and cell viability, permeability, uptake, total reactive oxygen species/superoxide production, and intracellular acidity were measured. CSCNTs were less toxic than MWCNTs in both cell types over a 24-hour exposure period. The cytotoxicity of endocytosed MWCNTs varied according to cell type/size, while that of CSCNTs depended on tube length irrespective of cell type. CNT diameter and length influenced cell aggregation and injury extent. Intracellular acidity increased independently of lysosomal activity along with the number of vacuoles in BEAS-2B cells exposed for 24 hours to either CNT (concentration, 10 μg/mL). However, total reactive oxygen species/superoxide generation did not contribute to cytotoxicity. The results demonstrate that CSCNTs could be suitable for biological applications and that CNT shape and size can have differential effects depending on cell type, which can be exploited in the development of highly specialized, biocompatible CNTs.

In plain English

This laboratory study tested carbon nanotubes, not asbestos. The authors noted a safety concern: nanotube shape is similar to that of asbestos. Two lab-grown human cell lines were used: BEAS-2B bronchial epithelial cells and MESO-1 malignant pleural mesothelioma cells. For 24 hours the cells were exposed to 1, 10 or 50 µg/mL of six products. Three were multi-walled carbon nanotubes of different diameters (15, 80 and 150 nm), and three were cup-stacked carbon nanotubes of different lengths. Multi-walled nanotubes were more toxic than cup-stacked nanotubes in both cell lines. Cup-stacked nanotubes were not toxic to MESO-1 cells, except at 50 µg/mL of the two longer types. Membrane leakiness was measured as LDH release, scored against detergent-treated cells set at 100%. At 10 µg/mL it was highest in BEAS-2B cells with the thinnest multi-walled type, VGCF-X, at 77%. In MESO-1 cells the highest was 29%, with VGCF, the thickest type. Only VGCF-X raised total reactive oxygen species. The authors concluded that cup-stacked nanotubes were more biocompatible, though slightly toxic. They added that biocompatibility must be confirmed in each target cell type.

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 human cell lines grown in the laboratory: BEAS-2B bronchial epithelial cells (from the American Type Culture Collection) and ACC-MESO-1 malignant pleural mesothelioma cells (from RIKEN, Japan). No people or animals were studied.
• Exposure: Three multi-walled carbon nanotubes (VGCF-X, VGCF-S and VGCF, with diameters of 15, 80 and 150 nm) and three cup-stacked carbon nanotubes of different lengths (CS-L 20 to 80 µm, CS-S 0.5 to 20 µm, CS-M intermediate). They were dispersed in gelatin and given at 1, 10 or 50 µg/mL for 24 hours. No asbestos was tested.
• Main results:
  • In both cell lines, multi-walled nanotubes were more toxic than cup-stacked nanotubes
  • In BEAS-2B cells, the toxicity of cup-stacked nanotubes depended on concentration and length
  • In MESO-1 cells, cup-stacked nanotubes were not toxic except at 50 µg/mL of CS-L and CS-M
  • In MESO-1 cells, multi-walled nanotube toxicity was consistently lower than in BEAS-2B cells
  • Membrane permeability was measured as LDH release relative to positive-control cells treated with Triton X-100 detergent, whose permeability was defined as 100%
  • At 10 µg/mL, BEAS-2B cells were more permeable with multi-walled nanotubes (more than 50% of the positive control) than with cup-stacked nanotubes (less than 50%). The highest value was with VGCF-X, the thinnest multi-walled type, at 77% of the positive control.
  • At 10 µg/mL, MESO-1 cell permeability with both nanotube types was below 30% of the positive control. The highest value was with VGCF, the thickest (150 nm) multi-walled type, at 29%.
  • In BEAS-2B cells, nanotubes collected in lysosomes. In MESO-1 cells, nanotubes were not specifically associated with the lysosome and were spread through the cytoplasm.
  • VGCF-X was the only nanotube that increased total reactive oxygen species
  • In BEAS-2B cells at 1 µg/mL, intracellular acidity rose by 10.8% (VGCF), 7.5% (VGCF-S) and 17.5% (VGCF-X), and by less than 5% for cup-stacked nanotubes. At 10 µg/mL, all nanotubes raised it by more than 10%.
  • In MESO-1 cells, acidity changes were mostly 10% or less, except with VGCF and VGCF-S at 50 µg/mL
• The authors' conclusion: The authors concluded that cup-stacked nanotubes were more biocompatible than multi-walled nanotubes, though slightly toxic. They found that toxicity depended on nanotube shape (length, diameter, aggregation) and on cell type. They concluded that biocompatibility must be confirmed in each target cell type.
• Limitations the authors state:
  • The study could not clarify how autophagy was triggered
  • Acidity could not be measured in BEAS-2B cells exposed to 50 µg/mL multi-walled nanotubes, because too few living cells remained

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Reactive Oxygen Species (ROS), Superoxide.

Related studies

• Effect of dispersants of multi-walled carbon nanotubes on cellular uptake and biological responses — H. Haniu, N. Saito, et al. (2011)
• Endocytosis of Multiwalled Carbon Nanotubes in Bronchial Epithelial and Mesothelial Cells — K. Maruyama, H. Haniu, et al. (2015)
• Carbon nanotube-based biomaterials for orthopaedic applications — K. Aoki, N. Ogihara, et al. (2020)
• Carboxylated short single-walled carbon nanotubes but not plain and multi-walled short carbon nanotubes show in vitro genotoxicity — M. Mrakovcic, C. Meindl, et al. (2015)
• Size- and shape-dependent pleural translocation, deposition, fibrogenesis, and mesothelial proliferation by multiwalled carbon nanotubes — J. Xu, D.B. Alexander, et al. (2014)
• The mechanism of pleural inflammation by long carbon nanotubes: interaction of long fibres with macrophages stimulates them to amplify pro-inflammatory responses in mesothelial cells — F.A. Murphy, A. Schinwald, et al. (2012)

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