Dissolution Reaction and Surface Modification of UICC Amosite in Mimicked Gamble's Solution: A Step towards Filling the Gap between Asbestos Toxicity and Its Crystal Chemical Features

Our plain-English summary of Dissolution Reaction and Surface Modification of UICC Amosite in Mimicked Gamble's Solution: A Step towards Filling the Gap between Asbestos Toxicity and Its Crystal Chemical Features, by A. Pacella, P. Ballirano, M.C. Di Carlo, et al (Nanomaterials, 2023).

The study

• Authors: A. Pacella, P. Ballirano, M.C. Di Carlo, M. Fantauzzi, A. Rossi, E. Nardi, C. Viti, L. Arrizza, A. Campopiano, A. Cannizzaro, A. Bloise, M.R. Montereali
• Journal: Nanomaterials
• Published: 2023;13(22)
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This study focuses on the dissolution process and surface characterization of amosite fibres following interaction with a mimicked Gamble's solution at a pH of 4.5 and T = 37 °C, up to 720 h. To achieve this, a multi-analytical approach was adopted, and the results were compared to those previously obtained on a sample of asbestos tremolite and UICC crocidolite, which were investigated under the same experimental conditions. Combining surface chemical data obtained by XPS with cation release quantified by ICP-OES, an incongruent behaviour of the fibre dissolution was highlighted for amosite fibres, similarly to asbestos tremolite and UICC crocidolite. In particular, a preferential release of Mg and Ca from the amphibole structure was observed, in agreement with their Madelung site energies. Notably, no Fe release from amosite fibres was detected in our experimental conditions (pH of 4.5 and atmospheric pO2), despite the occurrence of Fe(II) at the M(4) site of the amphibole structure, where cations are expected to be rapidly leached out during mineral dissolution. Moreover, the oxidation of both the Fe centres initially present on the fibre surface and those promoted from the bulk, because of the erosion of the outmost layers, was observed. Since biodurability (i.e., the resistance to dissolution) is one of the most important toxicity parameters, the knowledge of the surface alteration of asbestos possibly occurring in vivo may help to understand the mechanisms at the basis of its long-term toxicity.

In plain English

This was a laboratory experiment on fibres, not a study of people. The authors placed 20 mg of UICC amosite asbestos (from the Penge mine, South Africa) in 40 mL of mimicked Gamble's solution, a simulated biological fluid, at pH 4.5 and 37 degrees Celsius for up to one month (720 hours). They then examined the fibres and liquid with several microscopy and chemical techniques. Silicon and magnesium in the liquid rose with time. Magnesium and calcium were lost preferentially from the fibre surface, so the fibres dissolved unevenly. The authors found no iron leaching from the amosite fibres. They attributed the early iron release, and at least part of the calcium, to ankerite, a minor accompanying mineral that dissolved completely; calcium release exceeded what ankerite alone could explain. Surface iron became partly oxidised in the first hour. The bulk crystal structure showed no significant change. The authors compared a surface-adjusted dissolution rate with their earlier results for UICC crocidolite and asbestos tremolite, tested identically. They concluded that amosite has intermediate biodurability, between crocidolite (lowest) and asbestos tremolite (highest).

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) dissolution experiment on asbestos fibres in a simulated fluid, compared with the authors' earlier results for other amphiboles
• Who was studied: A single standard sample of amosite (fibrous grunerite) from the Penge mine, South Africa, supplied by the UICC. There were no human or animal subjects.
• Exposure: 20 mg of UICC amosite incubated with gentle shaking in 40 mL of mimicked Gamble's solution (MGS) at pH 4.5 and 37 degrees Celsius for up to 1 month (720 h)
• Main results:
  • Silicon and magnesium released into the solution increased with incubation time. Silicon rose from 57(1) mg/kg up to 2169(62), and magnesium from 394(3) mg/kg up to 985(36) mg/kg.
  • Dissolution was incongruent: the surface of the leached amosite fibres became depleted in magnesium and calcium
  • No iron leaching from the amosite fibres was indicated under the experimental conditions
  • The iron and at least a fraction of the calcium released were ascribed to dissolution of a small amount of the accessory mineral ankerite, which dissolved completely. The calcium released was higher than ankerite dissolution alone would explain.
  • Calcium released exceeded the amount expected from ankerite dissolution alone
  • In the first hour, the surface Fe(II)-O signal fell from about 70% to about 60% of the total iron peak area. Over the same hour, the Fe(III)-O signal rose from about 3% to about 18%. The signals then stayed almost constant.
  • The bulk crystal structure of the amosite showed no significant changes after one month
  • An ultrathin amorphous film about 10 to 30 nm wide surrounded the amosite fibres both before and after incubation
  • The surface-area-normalised silicon dissolution rate for amosite was 0.002 micromoles per hour per square metre (R2 = 0.99). This was between the values from the authors' earlier work for UICC crocidolite (0.007) and asbestos tremolite (0.0004).
• The authors' conclusion: The authors concluded that amosite fibres have an intermediate biodurability, between crocidolite (lowest) and asbestos tremolite (highest), despite a similar dissolution process
• Limitations the authors state:
  • The authors noted that further work treating fibres with real lung fluids is in progress, to give a more detailed picture of surface changes in the body
  • Because of the small calcium content in the amosite structure, the authors could not rule out that some calcium leached from the fibres rather than from ankerite

Topics

Medical terms in this study, explained in our Lexicon: UICC, Amosite, Tremolite, Crocidolite, Cation, Amphibole Group.

Related studies

• Surface and bulk modifications of amphibole asbestos in mimicked gamble's solution at acidic PH — A. Pacella, P. Ballirano, et al. (2021)
• Factors involved in the cytotoxicity of UICC amosite towards macrophages — R. Davies, D.M. Griffiths, et al. (1983)
• Bridging the gap between toxicity and carcinogenicity of mineral fibres by connecting the fibre crystal-chemical and physical parameters to the key characteristics of cancer — A.F. Gualtieri (2021)
• Modification of the in vitro activities of amosite asbestos by surface derivatization — P.H. Evans, R.C. Brown, et al. (1983)
• Practical steps towards the prevention of bronchial carcinoma — R. Doll (1970)
• Personalized Oncolytic Therapy: The Next Step Toward the Successful Clinical Application of Vaccine-Strain Measles Viruses for Cancer Therapy? — T. Peikert (2020)

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