Novel method using hybrid markers: development of an approach for pulmonary measurement of multi-walled carbon nanotubes

Our plain-English summary of Novel method using hybrid markers: development of an approach for pulmonary measurement of multi-walled carbon nanotubes, by M. Ohnishi, H. Yajima, T. Kasai, et al (Journal of Occupational Medicine and Toxicology, 2013).

The study

• Authors: M. Ohnishi, H. Yajima, T. Kasai, Y. Umeda, M. Yamamoto, S. Yamamoto, H. Okuda, M. Suzuki, T. Nishizawa, S. Fukushima
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2013;8(1):30
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Multi-walled carbon nanotubes (MWCNT)s are suspected to induce pulmonary and pleural cancers due to their asbestos-like configurations. Therefore, accurate measurement of inhaled nanotubes in target organs is crucial for assessing cancer risk. Conventionally, nanotubes are measured after combustion at high temperature for conversion into CO2; however, the sensitivity is poor and the method lacks versatility. We have therefore developed a novel approach using hybrid markers for nanotube analysis, featuring high sensitivity and the capacity to conduct repeated analyses. The method involves adsorption of markers to nanotubes, followed by their desorption and assessment by means of high performance liquid chromatography (HPLC).

Methods: Recovery of MWCNT from rat lungs was conducted, and pulmonary MWCNT amounts were determined using rats intratracheally-exposed to MWCNT aerosol at 5 mg/m3 for 6 hours/day.

Results: The correlation coefficient for the calibration curve of MWCNT weight and the HPLC area was 0.9991. Consequently, the lower quantitation limit yielded was 0.2 μg. The recovery was 92-98% at approximately 0.4-2.0 μg demonstrating that MWCNTs in the lung could be measured accurately and precisely.

Conclusions: We have developed a novel method using a hybrid marker approach for nanotube analysis, featuring very high sensitivity and the capacity to conduct repeated analyses. We further confirmed correlations between the amounts of nanotubes and markers and pulmonary nanotube measurement demonstrated that trace amounts could be detected with values closely relating to the administered dose, verifying that the method is sensitive and precise.

In plain English

This laboratory methods paper described a new way to measure multi-walled carbon nanotubes (MWCNTs), which the authors noted are suspected of asbestos-like effects, in rat lungs. Lungs were dissolved, and a fluorescent marker (benzo[ghi]perylene) was attached to the recovered nanotubes, then washed off and measured by liquid chromatography. The calibration curve had a correlation coefficient of 0.9991, and the lowest amount that could be reliably quantified was 0.2 μg. When known amounts were added to rat lungs, recovery was 92.5% at about 0.4 μg, 93.0% at 1.0 μg and 98.0% at 2.0 μg. In 5 rats given 2 μg into the windpipe, the text reported 0.68 μg (34.3%) in the right lung, 0.96 μg (48.5%) in the left lung and 0.34 μg (17.2%) in the trachea, though it also said the right lung held more. In rats exposed by inhalation at a target of 5 mg/m3 for six hours, left-lung amounts fell to about half by day 1 and declined further through day 56. The authors concluded the method offers very accurate measurement of MWCNTs. Disease was not studied.

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 method development with animal experiments in rats: a spiked-lung recovery test, an intratracheal administration test, and a single whole-body inhalation exposure with follow-up
• Who was studied: Male F344/DuCrlCrlj rats from Charles River Japan, studied at the Japan Bioassay Research Center. Five rats had their lungs removed and spiked with MWCNT for the recovery test. Five rats received MWCNT by intratracheal administration. Twenty-five rats were exposed by inhalation, with groups of 5 necropsied at the end of exposure and at 1, 7, 28 or 56 days afterwards. In the inhalation test, left lungs were used for measurement. Study dates are not given.
• Exposure: Multi-walled carbon nanotubes (MWNT-7, Hodogaya Chemical, Lot No. 080126), used unpurified. Doses were 2 μg per animal by intratracheal administration, and whole-body inhalation of MWCNT aerosol at a target concentration of 5 mg/m3 for 6 hours. No asbestos was studied.
• Main results:
  • Calibration of the method: the lower quantitation limit (the smallest amount reliably quantified) was 0.2 μg, and the correlation coefficient of the calibration curve was 0.9991.
  • Recovery of known amounts of MWCNT added to rat lungs was 92.5% at approximately 0.4 μg, 93.0% at 1.0 μg, and 98.0% at 2.0 μg.
  • In rats given 2 μg MWCNT intratracheally, the text reports 0.68 μg (34.3%) collected from the right lung, 0.96 μg (48.5%) from the left lung, and 0.34 μg (17.2%) from the trachea. The figure gives a total of 1.98 μg (99.0%).
  • In rats after whole-body inhalation exposure, MWCNT amounts, measured in the left lung, decreased to approximately one half on day 1 after exposure, with further gradual decreases on days 7, 28 and 56. The numbers are shown only in a graph.
  • The authors compared their lower quantitation limit of 0.2 μg with about 1 μg for an earlier combustion-based method by other researchers (Tamura et al.).
• The authors' conclusion: The authors concluded that their hybrid-marker method offers a new approach for very accurate measurement of multi-walled carbon nanotubes and is applicable to measuring nanotubes in the lungs of animals.

Related studies

• Thirteen-week study of toxicity of fiber-like multi-walled carbon nanotubes with whole-body inhalation exposure in rats — T. Kasai, Y. Umeda, et al. (2015)
• Long-term pulmonary exposure to multi-walled carbon nanotubes promotes breast cancer metastatic cascades — X. Lu, Y. Zhu, et al. (2019)
• Epithelial-mesenchymal transition involved in pulmonary fibrosis induced by multi-walled carbon nanotubes via TGF-beta/Smad signaling pathway — T. Chen, H. Nie, et al. (2014)
• 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)
• Pleural translocation and lesions by pulmonary exposed multi-walled carbon nanotubes — Q. Wang, Q. Wang, et al. (2020)
• In vitro chromosomal aberrations induced by various shapes of multi-walled carbon nanotubes (MWCNTs) — T. Sasaki, M. Asakura, et al. (2016)

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