Synthesis of Ni-Doped Tremolite Fibers to Help Clarify the Aetiology of the Cytotoxic Outcome of Asbestos

Our plain-English summary of Synthesis of Ni-Doped Tremolite Fibers to Help Clarify the Aetiology of the Cytotoxic Outcome of Asbestos, by A. Bloise, E. Giorno, D. Miriello, et al (Nanomaterials, 2023).

The study

• Authors: A. Bloise, E. Giorno, D. Miriello, N. Godbert
• Journal: Nanomaterials
• Published: 2023;13(8)
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos fibers act as complex crystal-chemical reservoirs susceptible of releasing potentially toxic elements (such as ions impurities) into the lung cellular environment during permanency and dissolution. To comprehend the exact pathological mechanisms that are triggered upon inhalation of asbestos fibers, in vitro studies on possible interactions between the mineral and the biological system have been carried out mostly by using natural asbestos. However, this latter comprises intrinsic impurities such as Fe2+/Fe3+ and Ni2+ ions, and other eventual traces of metallic pathogens. Furthermore, often, natural asbestos is characterized by the co-presence of several mineral phases, fiber dimensions of which are randomly distributed in width and in length. For these reasons, it is albeit challenging to precisely identify toxicity factors and to define the accurate role of each factor in the overall pathogenesis of asbestos. In this regard, the availability of synthetic asbestos fibers with accurate chemical composition and specific dimensions for in vitro screening tests would represent the perfect tool to correlate asbestos toxicity to its chemico-physical features. Herein, to palliate such drawbacks of natural asbestos, well-defined Ni-doped tremolite fibers were chemically synthesized in order to offer biologists adequate samples for testing the specific role of Ni2+ in asbestos toxicity. The experimental conditions (temperature, pressure, reaction time and water amount) were optimized to produce batches of asbestos fibers of the tremolite phase, with uniformly distributed shape and dimensions and a controlled content of Ni2+ metal ions.

In plain English

This was a laboratory chemistry study. The authors, at the University of Calabria in Italy, made synthetic tremolite asbestos fibers containing a controlled amount of nickel. The fibers were meant as test samples for later cell studies on the role of nickel in asbestos toxicity. They heated mixtures of silica and magnesium, calcium and nickel oxides with water under high temperature and pressure. Across seven runs they varied temperature (780 to 830 degrees C), pressure (1.1 to 2.4 kbar), reaction time (4 to 16 days) and water. Only run TN8 (800 degrees C, 2.4 kbar, 16 days, 8% water) produced nickel-doped tremolite with no other minerals. The authors measured 200 fibers per run. The text gives average widths of 0.15 to 0.29 micrometers, but Table 1 lists 0.30 for run TN5. In TN8, 93.0% of 200 measured fibers were under 0.25 micrometers wide; the text says more than 93%. Nickel content ranged from 0.4 to 1.2 atoms per formula unit. Based only on fiber size, the authors concluded that most of the synthesized fibers may be considered potentially carcinogenic. They did not test the fibers on cells or animals.

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 synthesis and mineralogical characterization study (hydrothermal synthesis of fibers; no biological testing)
• Who was studied: No human or animal subjects. Seven synthesis runs (TN2 to TN8) of nickel-doped tremolite fibers, each performed in triplicate, at the University of Calabria, Italy
• Exposure: No exposure was studied. The material made was synthetic nickel-doped tremolite asbestos fibers, grown at 780 to 830 degrees C and 1.1 to 2.4 kbar, over 4 to 16 days
• Main results:
  • Only run TN8 (800 degrees C, 2.4 kbar, 16 days, 8% water) produced nickel-doped tremolite as a single mineral phase. The other runs also contained other minerals, such as nickel-doped talc, diopside or forsterite.
  • The authors measured 200 fibers per run. The text reports an overall average width of 0.20 micrometers, with run averages ranging from 0.15 to 0.29 micrometers. Table 1, however, lists an average width of 0.30 micrometers for run TN5.
  • In run TN8, 93.0% of the 200 measured fibers were narrower than 0.25 micrometers, according to Figure 9. The Results text describes this as more than 93%.
  • In run TN5, 68% of fibers were wider than 0.25 micrometers.
  • Fibers were generally longer than 5 micrometers. The longest fibers, more than 2 mm long, were seen in run TN8.
  • Chemical analysis found silicon, magnesium, calcium and nickel, with no other impurity elements. Nickel content ranged from 0.4 to 1.2 atoms per formula unit. Only in run TN8 did the nickel content match the starting mixture.
  • Raman spectra of TN8 fibers showed shifts toward lower wavenumbers compared with pure synthetic tremolite. The authors attributed these shifts to nickel in the crystal structure.
• The authors' conclusion: The authors concluded that the fibers could serve as standard samples for in vitro tests on the role of nickel in tremolite asbestos toxicity, and that the single-phase TN8 fibers were more suitable for starting such tests. Based on measured size alone, they concluded that most of the synthesized fibers may be considered potentially carcinogenic.
• Limitations the authors state:
  • Because the long fibers were entangled, the authors could not accurately count and measure them.
  • Except in run TN8, other minerals formed and shifted the nickel content of the tremolite away from that of the starting mixture.

Topics

Medical terms in this study, explained in our Lexicon: Tremolite, Fiber Dimensions.

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