Cytotoxic effects of aggregated nanomaterials

Our plain-English summary of Cytotoxic effects of aggregated nanomaterials, by K. Soto, K.M. Garza, L.E. Murr (Acta Biomaterialia, 2007).

The study

• Authors: K. Soto, K.M. Garza, L.E. Murr
• Journal: Acta Biomaterialia
• Published: 2007;3(3):351-8
• Cited by: 173 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study deals with cytotoxicity assays performed on an array of commercially manufactured inorganic nanoparticulate materials, including Ag, TiO(2), Fe(2)O(3), Al(2)O(3), ZrO(2), Si(3)N(4), naturally occurring mineral chrysotile asbestos and carbonaceous nanoparticulate materials such as multiwall carbon nanotube aggregates and black carbon aggregates. The nanomaterials were characterized by TEM, as the primary particles, aggregates or long fiber dimensions ranged from 2nm to 20microm. Cytotoxicological assays of these nanomaterials were performed utilizing a murine alveolar macrophage cell line and human macrophage and epithelial lung cell lines as comparators. The nanoparticulate materials exhibited varying degrees of cytoxicity for all cell lines and the general trends were similar for both the murine and human macrophage cell lines. These findings suggest that representative cytotoxic responses for humans might be obtained by nanoparticulate exposures to simple murine macrophage cell line assays. Moreover, these results illustrate the utility in performing rapid in vitro assays for cytotoxicity assessments of nanoparticulate materials as a general inquiry of potential respiratory health risks in humans.

In plain English

This was a short-term laboratory study of cells grown in culture plates (in vitro), carried out at the University of Texas at El Paso. The authors exposed three cell lines to manufactured nanoparticle materials: mouse lung macrophages (RAW 264.7), human macrophages (THB-1) and human lung epithelial cells (A549). The materials included silver, titanium dioxide (anatase and rutile forms), iron oxide, aluminum oxide, zirconium oxide, silicon nitride, black carbon and two kinds of multiwall carbon nanotubes. Chrysotile asbestos was used as a positive control. At 5 micrograms per milliliter, almost all the materials were toxic to the mouse macrophages compared with controls, and silver was particularly toxic. Neither form of titanium dioxide was toxic to these cells. The human macrophages gave very similar results. The human epithelial cells were more affected: in these cells, black carbon and both nanotube types had an effect equivalent to chrysotile asbestos. The authors found no correlation between toxicity and the materials' surface area. The authors concluded that the mouse and human cell results corresponded. They said the findings carried no implications for human health except to caution against ingesting large concentrations of nanoparticles.

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: Short-term laboratory (in vitro) cell culture cytotoxicity experiment comparing a mouse cell line with human cell lines
• Who was studied: Three cell lines, studied at the University of Texas at El Paso: a mouse (murine) alveolar macrophage cell line (RAW 264.7), a human alveolar macrophage cell line the article calls THB-1, and a human lung epithelial cell line (A549)
• Exposure: Commercially manufactured nanoparticle materials (silver, TiO2 in anatase and rutile forms, Fe2O3, Al2O3, ZrO2, Si3N4), black carbon, two types of multiwall carbon nanotubes, and chrysotile asbestos as a positive control. Cells were tested at 5 micrograms per milliliter, and also in a series of dilutions starting at 10 micrograms per milliliter, with viability read after 48 hours of incubation.
• Main results:
  • In mouse macrophages at 5 micrograms per milliliter, almost all materials, including the carbon-based ones, were toxic relative to control media and DMSO. Neither anatase nor rutile TiO2 showed a cytotoxic response.
  • Silver (Ag-1) was particularly cytotoxic to the mouse lung macrophage cell line.
  • The human macrophage (THB-1) cell line gave very similar results to the mouse macrophage cell line.
  • In the human epithelial (A549) cells the materials had a greater toxic effect. Black carbon and the two multiwall carbon nanotube types had an effect equivalent to chrysotile asbestos.
  • In the human epithelial cells, both anatase and rutile TiO2 showed a slight cytotoxic effect.
  • The authors also measured the concentration that killed half the cells. On this measure, in mouse macrophages, Al2O3, ZrO2, Si3N4, black carbon and the carbon nanotube aggregates were as cytotoxic as the asbestos. Similar results were shown for human macrophages.
  • In the human epithelial cells, the carbon-based materials (black carbon and both nanotube types) caused cell death at lower concentrations (2.5 micrograms per milliliter) than in the mouse and human macrophages.
  • There was no correlation between specific surface area and the relative cytotoxicity ranking. Particle or aggregate shape was also not correlated with cytotoxicity.
• The authors' conclusion: The authors concluded that the mouse macrophage results corresponded to the results in human lung macrophage and epithelial cells. They stated there were no implications for health effects in humans except to caution against ingesting large concentrations of nanoparticulates.
• Limitations the authors state:
  • The results are very short term and were obtained in vitro.
  • Cell lines can respond differently from animal tissue and from the normal human body.
  • The electron microscope images may not show how the materials actually looked once suspended in the culture medium.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Fiber Dimensions, Alveolar Macrophage, Macrophage.

Related studies

• Cytotoxicity assessment of some carbon nanotubes and related carbon nanoparticle aggregates and the implications for anthropogenic carbon nanotube aggregates in the environment — L.E. Murr, K.M. Garza, et al. (2005)
• Cell entry of one-dimensional nanomaterials occurs by tip recognition and rotation — X. Shi, A. von dem Bussche, et al. (2011)
• A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials — V.C. Sanchez, P. Weston, et al. (2011)
• Cytotoxicity and reactive oxygen species generation from aggregated carbon and carbonaceous nanoparticulate materials — K.M. Garza, K.F. Soto, et al. (2008)
• Toxicity evaluations of various carbon nanomaterials — M. Uo, T. Akasaka, et al. (2011)
• Biopersistent fiber-induced inflammation and carcinogenesis: lessons learned from asbestos toward safety of fibrous nanomaterials — H. Nagai, S. Toyokuni (2010)

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