Stability of mineral fibres in contact with human cell cultures. An in situ μXANES, μXRD and XRF iron mapping study

Our plain-English summary of Stability of mineral fibres in contact with human cell cultures. An in situ μXANES, μXRD and XRF iron mapping study, by S. Pollastri, A.F. Gualtieri, R. Vigliaturo, et al (Chemosphere, 2016).

The study

• Authors: S. Pollastri, A.F. Gualtieri, R. Vigliaturo, K. Ignatyev, E. Strafella, A. Pugnaloni, A. Croce
• Journal: Chemosphere
• Published: 2016;164:547-557
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Relevant mineral fibres of social and economic importance (chrysotile UICC, crocidolite UICC and a fibrous erionite from Jersey, Nevada, USA) were put in contact with cultured diploid human non-tumorigenic bronchial epithelial (Beas2B) and pleural transformed mesothelial (MeT5A) cells to test their cytotoxicity. Slides of each sample at different contact times up to 96 h were studied in situ using synchrotron XRF, μ-XRD and μ-XAS (I18 beamline, Diamond Light Source, UK) and TEM investigations. XRF maps of samples treated for 96 h evidenced that iron is still present within the chrysotile and crocidolite fibres and retained at the surface of the erionite fibres, indicating its null to minor mobilization in contact with cell media; this picture was confirmed by the results of XANES pre-edge analyses. μ-XRD and TEM data indicate greater morphological and crystallinity modifications occurring in chrysotile, whereas crocidolite and erionite show to be resistant in the biological environment. The contact of chrysotile with the cell cultures seems to lead to earlier amorphization, interpreted as the first dissolution step of these fibres. The formation of such silica-rich fibre skeleton may prompt the production of HO in synergy with surface iron species and could indicate that chrysotile may be much more reactive and cytotoxic in vitro in the (very) short term whereas the activity of crocidolite and erionite would be much more sluggish but persistent in the long term.

Copyright © 2016 Elsevier Ltd. All rights reserved.

In plain English

This laboratory study examined three mineral fibres, UICC chrysotile, UICC crocidolite and fibrous erionite from Jersey, Nevada, USA, after contact with cultured human cells. The fibres were added to bronchial epithelial cells (Beas2B) and pleural mesothelial cells (MeT5A) for up to 96 hours. Only the 24-hour and 96-hour samples were analysed, using synchrotron X-ray methods and electron microscopy of the fibres. After 96 hours, iron was still present in all the fibres, and its chemical form (mostly ferric iron) showed no major change. Chrysotile changed most: its diffraction peaks broadened, and in mesothelial cultures it appeared largely amorphous (it had lost its crystal structure) while keeping its overall shape. Crocidolite showed very minor change, and erionite appeared stable. The authors concluded that chrysotile may be more reactive and cytotoxic in the short term, while crocidolite and erionite persist longer. This was their interpretation; the article reports no measurements of harm to the cells. The authors noted that their preparation method could dissolve asbestos bodies, so asbestos bodies were 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 (in vitro) experiment: mineral fibres exposed to human cell cultures, then the fibres were examined with synchrotron X-ray fluorescence mapping, micro-XANES, micro-X-ray diffraction and transmission electron microscopy
• Who was studied: Three fibre samples (UICC standard chrysotile 'B', UICC standard crocidolite, fibrous erionite-Na from Jersey, Nevada, USA) placed in two human cell lines: MeT5A (SV40-immortalized pleural mesothelial cells) and Beas2B (SV40-immortalized bronchial epithelial cells)
• Exposure: Chrysotile, crocidolite and erionite fibres suspended in culture medium and added to the cells for 24, 48, 72 and 96 hours; only the 24-hour and 96-hour samples were analysed
• Main results:
  • After 96 hours in both cell cultures, iron was still present in all samples: within the crystal structure of chrysotile and crocidolite, and retained at the surface of the erionite fibres. The authors read this as absent or minor movement of iron out of the fibres.
  • For all fibres, in both cultures and at both times, iron was mainly ferric iron in octahedral position, with no major change in its chemical environment compared with the raw samples
  • For crocidolite, iron appeared slightly oxidized compared with the untreated sample
  • The X-ray diffraction peak-broadening parameter (Lx) rose markedly for chrysotile from 24 to 96 hours: from 25(6) to 51(8) in MeT5A and from 44(8) to 68(10) in Beas2B. It rose only slightly for crocidolite (10(1) to 12(2) in MeT5A; 6(2) to 12(2) in Beas2B) and for erionite (6(1) to 8(3) in MeT5A).
  • Under electron microscopy, chrysotile after 96 hours with MeT5A kept its overall shape but gave diffraction patterns indicating amorphous material. Crocidolite and erionite showed good crystallinity even after 96 hours.
  • Peak broadening of chrysotile was more intense with the bronchial Beas2B cells than with the mesothelial MeT5A cells
• The authors' conclusion: The authors concluded that the loss of crystal structure in chrysotile is the first step of its dissolution, and that, if their reasoning is correct, chrysotile may be much more reactive and cytotoxic in vitro in the short term than crocidolite and erionite, which they described as biopersistent
• Limitations the authors state:
  • Because of limited beam time, only the 24-hour and 96-hour samples were analysed
  • The iron maps of the erionite fibres were not of sufficient quality to be shown
  • The method used to remove biological material may dissolve asbestos bodies, so asbestos bodies were not investigated
  • Silicon, sodium, aluminium and magnesium could not be detected with the beamline used
  • Data quality did not allow a full Rietveld structure refinement
  • For chrysotile, a direct iron comparison with raw samples was not possible because suitable raw-sample data were unavailable
  • A thin iron-rich amorphous layer or nanoparticles on crocidolite could not be detected at the resolution of these experiments

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, UICC, Crocidolite, erionite.

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