Carbon nanotube-based biomaterials for orthopaedic applications

Our plain-English summary of Carbon nanotube-based biomaterials for orthopaedic applications, by K. Aoki, N. Ogihara, M. Tanaka, et al (Journal of Materials Chemistry. B, 2020).

The study

• Authors: K. Aoki, N. Ogihara, M. Tanaka, H. Haniu, N. Saito
• Journal: Journal of Materials Chemistry. B
• Published: 2020;8(40):9227-9238
• Type of article: Review
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Carbon nanotubes (CNTs) are cylindrical tubular nanomaterials made of carbon with excellent electrical conductivity, thermal conductivity, and mechanical strength. The material is applied to improve performance in various industrial products. CNTs have been widely researched and developed as biomaterials that can offer high function, performance, and durability in orthopedic applications. However, the use of CNTs as biomaterials must be administered with caution, as the fibrous nanomaterial may be carcinogenic due to its similar size and shape to asbestos. In this review article, we examine the potential clinical application of CNTs in orthopedic surgery. We first provide an overview of biocompatibility and carcinogenicity studies of CNTs with a focus on their effects on the bone, joint, and respiratory system. Furthermore, we introduce CNT-based biomaterials for orthopedic applications that have been reported in the literature, including scaffolds for bone and cartilage regeneration, composites that enhance the performance of biomaterials, CNT coatings, and devices for treating musculoskeletal tumors.

In plain English

This was a review article by Japanese researchers about carbon nanotubes (CNTs), which are manufactured carbon fibers. The authors noted that CNTs may cause cancer because their size and shape resemble asbestos. The article described earlier cell and animal studies, including the authors' own work, and orthopaedic uses such as bone scaffolds, bone cement and joint-surface ceramics. In one cited study using human peritoneal mesothelial cells, crocidolite asbestos entered the cells, while multi-walled CNTs only attached to the cell surface. In another, multi-walled CNTs injected into the abdomen of a genetically modified mouse used for cancer testing produced mesothelioma in the abdominal cavity. In a third, rats exposed by pharyngeal aspiration developed malignant mesothelioma and lung tumours. In a cited rasH2 mouse study, the multi-walled CNT group had a 100% survival rate and developed inflammatory pseudo-tumours in the spleen. The authors suggested that bones and joints, which lack mesothelium, may show low carcinogenicity from CNTs. They said lung exposure is a greater concern in workplaces handling CNT materials. They concluded that the safety of each CNT biomaterial must be verified.

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: Narrative review of published cell, animal and materials studies on carbon nanotubes, including the authors' own earlier work
• Who was studied: Published laboratory studies in cells and animals. These included human bronchial epithelial cells, human peritoneal mesothelial cells, mouse bone cells, mice and rats, as well as studies of CNT-based orthopaedic materials. No search period or number of studies is stated.
• Exposure: Carbon nanotubes, mainly multi-walled carbon nanotubes (MWCNTs), and CNT-based materials. Asbestos (crocidolite) appears only as a comparison material in one cited cell study.
• Main results:
  • Cited study (Nagai et al.), human peritoneal mesothelial cells: crocidolite was taken up into the cells, whereas MWCNTs about 115 nm in diameter only attached to the cell surface.
  • Cited study (Takagi et al.), p53 heterozygous mice used for cancer testing: injecting MWCNTs into the abdomen produced mesothelioma in the abdominal cavity. Fullerene produced no tumours, and higher MWCNT doses increased the mesothelioma mortality rate.
  • Cited study (Suzui et al.), F344/Crj rats given MWCNTs by pharyngeal aspiration: malignant mesothelioma and lung tumours formed in the MWCNT group, and no tumours formed in the control (vehicle) group.
  • Cited study (Takanashi et al.), rasH2 mice: in the group given the carcinogen MNU, papillomas and malignant lymphomas formed and the survival rate was 60% at 26 weeks. In the MWCNT group, inflammatory pseudo-tumours developed in the spleen and the survival rate was 100%.
  • The authors suggested that because bones and joints lack mesothelium, the use of CNTs there may show low carcinogenicity.
  • The authors stated that respiratory exposure to CNTs is more of a problem in workplaces handling CNT-containing materials than in use for patients.
• The authors' conclusion: The authors concluded that the effects of nanomaterials such as CNTs on living organisms are unknown, and that the biocompatibility of each CNT biomaterial should be verified before clinical research.
• Limitations the authors state:
  • The authors stated that how these nanomaterials behave inside the body is not clearly understood and needs careful assessment of safety and toxicity.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic.

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)
• Induction of mesothelioma in p53+/- mouse by intraperitoneal application of multi-wall carbon nanotube — A. Takagi, A. Hirose, et al. (2008)
• Mechanisms of pulmonary toxicity and medical applications of carbon nanotubes: Two faces of Janus? — A.A. Shvedova, E.R. Kisin, et al. (2009)
• Re: Induction of mesothelioma in p53+/- mouse by intraperitoneal application of multi-wall carbon nanotube — G. Ichihara, V. Castranova, et al. (2008)
• Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes — Y. Grosse, D. Loomis, et al. (2014)

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