Asbestos-like pathogenicity of long carbon nanotubes alleviated by chemical functionalization

Our plain-English summary of Asbestos-like pathogenicity of long carbon nanotubes alleviated by chemical functionalization, by H. Ali-Boucetta, A. Nunes, R. Sainz, et al (Angewandte Chemie, 2013).

The study

• Authors: H. Ali-Boucetta, A. Nunes, R. Sainz, M.A. Herrero, B. Tian, M. Prato, A. Bianco, K. Kostarelos
• Journal: Angewandte Chemie
• Published: 2013;52(8):2274-8
• Cited by: 112 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Sometimes shorter is better: The apparent similarity between multi-walled carbon nanotubes (MWNTs) and asbestos fibers has generated serious concerns about their safety profile. The asbestos-like pathogenicity observed for long, pristine nanotubes (NTlong, see scheme) can be completely alleviated if their effective length is decreased as a result of chemical functionalization, such as with tri(ethylene glycol) (TEG).

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was a short-term experiment in mice testing whether chemically modifying long multi-walled carbon nanotubes changes the asbestos-like reactions they cause. The authors took long, unmodified nanotubes previously used by another research group and attached chemical chains to them in two ways, producing an octyl (alkyl) version (NT-Alkyl) and a tri(ethylene glycol) version (NT-TEG). Female C57BL/6 mice, in groups of 4 to 6, received one injection into the abdominal cavity of unmodified nanotubes, either modified type, long fiber amosite asbestos as a positive comparison, or the carrier liquid alone. They were examined after 24 hours or 7 days. Under the microscope, the unmodified sample had the longest tubes and NT-TEG the shortest. At 24 hours, unmodified nanotubes and NT-Alkyl significantly raised inflammatory white cells and protein in abdominal fluid, similar to amosite. NT-TEG did not. At 7 days, granulomas (clusters of inflammatory cells) were seen on the diaphragm with unmodified nanotubes, amosite and NT-Alkyl, but not with NT-TEG. The authors suggested that only chemical changes that shorten or untangle the nanotubes in water will help resolve long-fiber risks, and said more studies are needed.

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: Animal experiment: single injection into the abdominal (peritoneal) cavity of mice, with examination of inflammation at 24 hours and granuloma formation at 7 days
• Who was studied: Female C57BL/6 mice, six to eight weeks old, obtained from Harlan (Oxfordshire, UK); groups of 4 to 6 animals per material and time point; experiments approved by the UK Home Office
• Exposure: Long, unmodified (pristine) multi-walled carbon nanotubes (NTlong) previously used by Poland et al.; the same nanotubes chemically modified with octyl chains (NT-Alkyl) or with tri(ethylene glycol) chains (NT-TEG); long fiber amosite asbestos (LFA) as a positive control; 0.5% bovine serum albumin/saline as vehicle control. Each mouse received a single injection of the same printed dose of one material.
• Main results:
  • Nanotube length (semi-quantitative, from electron microscope images): the unmodified sample had the highest fraction of very long nanotubes; the NT-Alkyl sample was intermediate; the NT-TEG sample had the shortest length distribution
  • At 24 hours, unmodified nanotubes and NT-Alkyl caused a significant increase in polymorphonuclear white cells and protein in the abdominal lavage fluid compared with the vehicle control, similar to long fiber amosite
  • At 24 hours, NT-TEG did not significantly raise protein levels or total polymorphonuclear white cells, which the authors took to suggest no inflammatory response
  • At 7 days, tissue staining and electron microscopy of the diaphragm showed granulomatous inflammation with unmodified nanotubes, long fiber amosite and NT-Alkyl, but not with NT-TEG
• The authors' conclusion: The authors suggested that only chemical modifications that shorten or untangle the nanotubes when dispersed in water will help resolve the toxicological risks of long-fiber exposure. They said their study illustrates how chemical modification can reduce the reactivity of a specific type of long, pristine nanotube.
• Limitations the authors state:
  • The authors stated that more studies are needed to confirm their hypothesis that modifications which do not improve effective length and dispersibility will keep the nanotubes reactive
  • The authors described the nanotube length analysis as only semi-quantitative
  • The size distribution shown for the amosite fibers is thought to underestimate their length, because the fibers were longer than the microscope grid
  • The authors stated that other design features (surface charge, flexibility, molecular weight of attached groups) still need to be studied in more complex animal models

Related studies

• Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study — C.A. Poland, R. Duffin, et al. (2008)
• Threshold Rigidity Values for the Asbestos-like Pathogenicity of High-Aspect-Ratio Carbon Nanotubes in a Mouse Pleural Inflammation Model — D.K. Lee, S. Jeon, et al. (2018)
• Role of p53 in the chronic pulmonary immune response to tangled or rod-like multi-walled carbon nanotubes — K.S. Duke, E.A. Thompson, et al. (2018)
• Effect of surface functionalizations of multi-walled carbon nanotubes on neoplastic transformation potential in primary human lung epithelial cells — T.A. Stueckle, D.C. Davidson, et al. (2017)
• Long, needle-like carbon nanotubes and asbestos activate the NLRP3 inflammasome through a similar mechanism — J. Palomäki, E. Välimäki, et al. (2011)
• High-temperature calcined fullerene nanowhiskers as well as long needle-like multi-wall carbon nanotubes have abilities to induce NLRP3-mediated IL-1β secretion — H. Cui, W. Wu, et al. (2014)

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