A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly

Our plain-English summary of A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly, by R. Matassa, G. Familiari, M. Relucenti, et al (Scientific Reports, 2015).

The study

• Authors: R. Matassa, G. Familiari, M. Relucenti, E. Battaglione, C. Downing, A. Pacella, G. Cametti, P. Ballirano
• Journal: Scientific Reports
• Published: 2015;5:16757
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble's solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans.

In plain English

This laboratory study used electron microscopy to examine three erionite samples; no people or animals were studied. The samples were woolly erionite from Durkee, Oregon, USA; erionite from Rome, Oregon; and Rome fibres soaked for 4 months in Gamble's solution, a simulated lung fluid. In the Durkee sample, fibrils with a mean width of 16.0 nm lined up into flat, ribbon-like bundles 25 to 680 nm wide. The Rome sample formed thicker rod-like bundles, the thickest about 0.5 to 1.2 micrometres across, embedded in nontronite, an iron-bearing clay mineral. After soaking, the Rome fibres were slightly narrower, showed no iron, had lost the surrounding clay flakes and were partly non-crystalline, though isolated nontronite flakes remained elsewhere. The authors linked fibril size and defects to flexibility in the Durkee sample versus brittleness in the Rome sample. They concluded that fibre size and the tendency to split deserve attention when judging toxic effects, and that nontronite's role needs detailed study. High-resolution imaging failed because the electron beam damaged the fibres.

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 mineralogical study using transmission electron microscopy (TEM) with X-ray analysis (EDX), electron diffraction (SAED) and dark-field imaging, plus image simulation
• Who was studied: Three erionite mineral samples: woolly erionite-Na from Durkee, Oregon, USA (ED); erionite-Na from Rome, Oregon, USA (ER); and ER fibres leached in simulated lung fluid (ER4G). No human or animal subjects.
• Exposure: Erionite fibres, a fibrous zeolite. One sample of Rome erionite was leached for 4 months in Gamble's solution, a simulated lung fluid.
• Main results:
  • Durkee sample (ED): fibrils aggregated into ribbon-like bundles whose width ranged from 25 to 680 nm
  • Durkee sample (ED): single fibril diameters ranged from 15.5 to 16.5 nm, with a mean of 16.0 nm
  • Rome sample (ER): rod-like bundles, the thickest about 0.5 to 1.2 micrometres in diameter and the smallest 150 to 300 nm
  • Rome sample (ER): the flaky material around the fibres was identified as polycrystalline nontronite, an iron-bearing clay mineral, completely embedding the fibre
  • Leached Rome sample (ER4G): fibre diameter was slightly smaller than in untreated ER, attributed to partial digestion and removal of the embedding nontronite
  • Leached Rome sample (ER4G): no iron was detected on the fibres
  • Leached Rome sample (ER4G): the fibres were partly amorphised (partly lost their crystalline structure)
  • The authors attributed the different mechanical behaviour of the Durkee and Rome samples (flexibility versus brittleness) to the different fibril dimensions and defects
• The authors' conclusion: The authors concluded that attention should be paid to the toxicological effects related to erionite fibre dimensions and to the fibres' tendency to split, and that the role of nontronite needs to be investigated in detail.
• Limitations the authors state:
  • High-resolution TEM could not provide direct structural information because erionite was unstable under the electron beam
  • It was unclear whether nontronite actually dissolved during leaching, because isolated nontronite flakes were still found in the leached sample
  • The Rome samples could not be examined at 80 kV because of the adhering flaky material, so a lower voltage of 60 kV was used

Topics

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

Related studies

• Quantitative characterization of the mesothelioma-inducing erionite series minerals by transmission electron microscopy and energy dispersive spectroscopy — M. Dogan (2012)
• High incidence of lung cancer and malignant mesothelioma linked to erionite fibre exposure in a rural community in Central Mexico — M.A. Ortega-Guerrero, G. Carrasco-Núñez, et al. (2015)
• Geological occurrence, mineralogical characterization, and risk assessment of potentially carcinogenic erionite in Italy — M. Giordani, M. Mattioli, et al. (2017)
• New insights into the toxicity of mineral fibres: A combined in situ synchrotron μ-XRD and HR-TEM study of chrysotile, crocidolite, and erionite fibres found in the tissues of Sprague-Dawley rats — A.F. Gualtieri, N. Bursi Gandolfi, et al. (2017)
• Erionite bodies and fibres in bronchoalveolar lavage fluid (BALF) of residents from Tuzköy, Cappadocia, Turkey — P. Dumortier, L. Coplü, et al. (2001)
• Lung diseases due to environmental exposures to erionite and asbestos in Turkey — S. Emri, A. Demir, et al. (2002)

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