The adsorption of biological macromolecules by mineral dusts

Our plain-English summary of The adsorption of biological macromolecules by mineral dusts, by R. Desai, R.J. Richards (Environmental Research, 1978).

The study

• Authors: R. Desai, R.J. Richards
• Journal: Environmental Research
• Published: 1978;16(1-3):449-64
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Evidence is presented that the absorptive capacity of various mineral dusts (asbestos, quartz, treated titanium dioxide samples) for complex mixtures of organic macromolecules (serum proteins, pulmonary surfactant) may be explained as a sum of their specific surface area, which partly determines the amount of material adsorbed, and their surface chemistry, which determines the specificity of binding. Both “weak” and “strong” adsorption reactions were noted with serum proteins, the latter being considered as the most specific for each mineral and perhaps the most important physiologically. The implications of the observed adsorption phenomena to the reaction between mineral particles, organic macromolecules, and cells ih Ritz and i/l r~itro are discussed.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was a laboratory study of dust samples, not people. The authors measured how much protein from a serum-containing culture medium, and how much radioactively labelled rabbit serum proteins and lung surfactant, stuck to mineral dusts, and how much stayed after washing. The dusts included reference chrysotile, amosite, anthophyllite and crocidolite asbestos, ground (SFA) and magnesium-depleted chrysotile, quartz (Min-U-Sil), Brazilian silica, brucite and titanium dioxide. In a 30-second test, chrysotile bound far more protein than the other dusts and kept about 20% after water washes, a share similar to the amphiboles. After 24 hours, magnesium-depleted chrysotile initially bound more than ordinary chrysotile. Grinding chrysotile to the SFA form reduced its binding. Amosite, crocidolite and Min-U-Sil kept very similar sets of proteins, and anthophyllite differed from chrysotile. Of titanium dioxide samples with added trace metals, only the iron-containing one kept protein after washing. A titanium dioxide control dust also kept some. Chrysotile bound the most surfactant, only marginally more than the amphiboles. The authors concluded that binding may be explained by specific surface area together with surface chemistry.

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 measuring adsorption of proteins and lung surfactant onto mineral dust samples
• Who was studied: Mineral dust samples, not people: UICC reference samples of Rhodesian chrysotile A, Canadian chrysotile B, amosite, anthophyllite and crocidolite; SFA chrysotile; 20% and 80% magnesium-depleted chrysotile A; Min-U-Sil (quartz); Brazilian silica; brucite; titanium dioxide samples with added chromium, iron, niobium, nickel or aluminium; and a commercial (BDH) titanium dioxide used as a control dust. Rabbits were used only as a source of labelled serum proteins and lung surfactant.
• Exposure: Dusts were incubated with 20% foetal bovine serum plus Waymouth's culture medium (for 30 seconds, 60 minutes or 24 hours), with [3H]leucine-labelled rabbit serum proteins, or with 14C-labelled rabbit pulmonary surfactant. They were then washed with water, 0.01 M or 0.15 M NaCl, or Veronal-buffered saline.
• Main results:
  • After 30 seconds of incubation with culture medium, chrysotile bound far more protein material than any other dust tested in that experiment.
  • In the 30-second experiment, after water washes, chrysotile kept about 20% of the protein it had originally bound. This percentage was similar to the amphiboles.
  • After a 60-minute incubation, washed chrysotile retained more protein than it had after the 30-second incubation.
  • With 24-hour incubation, the amount of protein bound by chrysotile did not change, while the amounts bound by all other dusts increased.
  • In the 24-hour experiment, the 20% and 80% magnesium-depleted chrysotiles initially adsorbed more protein than unleached chrysotile. After washing, they kept amounts similar to ordinary chrysotile.
  • Grinding chrysotile to the SFA form reduced its protein-binding capacity, even though in theory it exposed the most surface area.
  • Most of the protein bound by the dusts had a molecular weight of about 70,000, corresponding to albumin.
  • After washing, chrysotile lost much of its albumin but strongly kept proteins of molecular weights 270,000 and 170,000.
  • Anthophyllite lost the high-molecular-weight bands (270,000 and 170,000) that chrysotile kept.
  • Crocidolite, amosite and Min-U-Sil gave very similar patterns of adsorbed proteins.
  • Of the titanium dioxide samples with added trace metals, all lost their adsorbed protein on washing except the sample containing iron oxide.
  • The separate commercial (BDH) titanium dioxide control dust also kept some labelled protein after washing.
  • Chrysotile bound the most lung surfactant, only marginally more than the amphiboles. Min-U-Sil and Brazilian silica bound the least.
  • Surfactant bound to dusts was largely removed by water washing, but not by 0.15 M NaCl or Veronal-buffered saline.
• The authors' conclusion: The authors concluded that the adsorptive capacities of the minerals may be explained by their specific surface area together with their surface chemistry. In their view, surface area partly controls how much is adsorbed, and surface chemistry determines which molecules are bound.
• Limitations the authors state:
  • The authors noted that the apparent increase in protein adsorbed at 60 minutes compared with 30 seconds may be due to differences in the protein and dust concentrations used.

Related studies

• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• The chemiluminescent response of human phagocytic cells to mineral dusts — I.P. Gormley, M.J. Kowolik, et al. (1985)
• Selective adsorption of serum proteins by chrysotile and crocidolite — F. Valerio, D. Balducci, et al. (1986)
• Adsorption of benzo(a)pyrene on to asbestos and manmade mineral fibres in an aqueous solution and in a biological model solution — P. Gerde, P. Scholander (1988)
• Measurement of reactive oxygen metabolites produced by human monocyte-derived macrophages exposed to mineral dusts — P. Nyberg, M. Klockars (1990)
• Fibrinolysis by rat mesothelial cells in vitro: the effect of mineral dusts at non-toxic doses — K. Donaldson, G.M. Brown, et al. (1988)

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