Different cellular responses evoked by natural and stoichiometric synthetic chrysotile asbestos

Gazzano, Elena; Foresti, Elisabetta; Lesci, Isidoro Giorgio; Tomatis, Maura; Riganti, Chiara; Fubini, Bice; Roveri, Norberto; Ghigo, Dario

doi:10.1016/j.taap.2004.11.021

Cited by 52 publications

(42 citation statements)

References 33 publications

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“…[8,9,19] Iron chelators reduce free radical release from asbestos, [5,14] although no direct correlation may be established between the amount of iron removal and the reactivity at the fiber surface, which depends not only on the amount of surface iron but also on its coordination and oxidation state and on the fiber micromorphology. [15,27,32,33] The incubation with F. oxysporum, similarly to the treatment with chelators, causes a decrement in HOC release, with some differences among the different asbestos types examined.…”

Section: Discussionmentioning

confidence: 99%

“…[16][17][18] Synthetic chrysotile with no iron in the structure was recently reported not to be cytotoxic toward human epithelial cells in a culture. [19] Iron extraction from asbestos fibers may also destabilize the lattice if the extraction proceeds for several layers below the fiber surface. As both the fibrous habit and the chemical reactivity are involved in asbestos pathogenicity, iron removal may be considered as a possible strategy to reduce asbestos-associated toxicity and to inactivate the fibers.…”

Section: Introductionmentioning

confidence: 99%

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Inorganic Materials and Living Organisms: Surface Modifications and Fungal Responses to Various Asbestos Forms

Daghino

Martino

Fenoglio

et al. 2005

Chemistry A European J

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In a previous study several strains of soil fungi were reported to remove iron in vitro from crocidolite asbestos, a process that was envisaged as a possible bioremediation route for asbestos-polluted soils. Here, we get some new insight into the chemical basis of the fiber/fungi interaction by comparing the action of the most active fungal strain Fusarium oxysporum on three kind of asbestos fibers--chrysotile, amosite, and crocidolite--and on a surface-modified crocidolite. None of the fibers examined significantly inhibited biomass production. Even the smallest fibrils were visibly removed from the supernatant following adhesion to fungal hyphae. F. oxysporum, through release of chelators, extracted iron from all fibers; the higher the amount of iron at the exposed surface, the larger the amount removed, that is, crocidolite > amosite >> chrysotile. When considering the fraction of total iron extracted, however, the ranking was chrysotile > crocidolite > amosite > heated crocidolite, because of the different accessibility of the chelators to the metal ions in the crystal structure. Chrysotile was the easiest to deplete of its metal content. Iron removal fully blunted HO* radical release from crocidolite and chrysotile but only partially from amosite. The removal, in a long-term experiment, of more iron than is expected to be at the surface suggests a diffusion of ions from the bulk solid towards the surface depleted of iron by fungal activity. Thus, if the fibers could be treated with a continuous source of chelators, iron extraction would proceed up to a full inactivation of free radical release. The fungal metabolic response of F. oxysporum grown in the presence of chrysotile, amosite and crocidolite revealed that new extracellular proteins are induced--including manganese-superoxide dismutase, the typical antioxidant defense--and others are repressed, upon direct contact with the fibers. The protein profile induced by heated crocidolite was different, a result suggesting a key role for the state of the fiber/hyphae interface in protein induction.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inorganic Materials and Living Organisms: Surface Modifications and Fungal Responses to Various Asbestos Forms

Daghino

Martino

Fenoglio

et al. 2005

Chemistry A European J

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“…This study has been developed along the following lines: 1) a stoichiometric, geoinspired, iron-free chrysotile nanofibre was synthesised by means of a hydrothermal procedure; [15] 2) the iron-free chrysotile sample [15] was compared to a natural chrysotile (UICC standard sample). Unlike the natural specimen, no cytotoxic, no oxidative stress and no DNA damage in several in vitro tests was reported upon contact with the synthetic iron-free nanofibre; [16] 3) an iron-doped synthetic chrysotile was consequently synthesised with the same synthesis procedure; 4) the iron-doped synthetic chrysotile was shown to be active in ROS production, to induce oxidative stress in vitro and to be as toxic as natural UICC chrysotile, thereby providing for the first time, without confounding factors, a direct cause-and-effect correlation between cellular toxicity and occurrence of iron in asbestos; [17] 5) a set of five Fe-doped synthetic chrysotile fibres was synthesised, and the fibres had features consistent with both natural and iron-free synthetic fibres; [18] Finally, as we report here, the set of fibres has been exploited to clarify the following issues: i) whether extremely low iron loadings (down to 0.67 wt %) are sufficient to trigger free-radical release, thus imparting toxic properties to synthetic nanofibres; ii) the effect of variation in iron-loading on radical release; and iii) last but not least, the correlation between position of iron active sites in the crystal lattice and their potential to generate free radicals. By adopting the well-known spin-trapping technique, which is associated with electron paramagnetic resonance spectroscopy (EPR), we have measured the amount and type of fibre-derived free-radical species by contacting chrysotile nanofibres with hydrogen peroxide and formate ion.…”

Section: Introductionmentioning

confidence: 98%

The Iron‐Related Molecular Toxicity Mechanism of Synthetic Asbestos Nanofibres: A Model Study for High‐Aspect‐Ratio Nanoparticles

Turci

Tomatis

Lesci

et al. 2010

Chemistry A European J

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Asbestos shares with carbon nanotubes some morphological and physico-chemical features. An asbestos-like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron-free model nanofibre previously found non-toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78 wt %. The relationship between fibre-induced free-radical generation and the physico-chemical characteristics of iron active sites was investigated with spin-trapping techniques on an aqueous suspension of the fibres and Mössbauer and EPR spectroscopies on the solids, respectively. The fully iron-free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. Mössbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra-framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon-centred radicals and the amount of rhombic-distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non-toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico-chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres.

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“…Given the multiplicity of factors that make a study on naturally occurring minerals complex, geoinspired chrysotile nanocrystals have been synthesized as a unique phase with definite structure, morphology and chemical composition to be used as a standard reference sample for the investigation of the molecular interaction between chrysotile fibres and biological systems [13,14]. The geoinspired synthetic chrysotile fibres with stoichiometric composition Mg 3 Si 2 O 5 (OH) 4 , in contrast to the natural ones, do not exert any significant cytotoxic effect [15]. Moreover, the interaction of this synthetic chrysotile with bovine serum albumin (BSA) and human serum albumin (HSA) has been investigated [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Adsorption of bovine serum albumin onto synthetic Fe-doped geomimetic chrysotile

Adamiano

Lesci

Fabbri

et al. 2015

J. R. Soc. Interface.

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Synthetic stoichiometric and Fe-doped geomimetic chrysotile nanocrystals represent a reference standard to investigate the health hazard associated with mineral asbestos fibres. Experimental evidence suggests that the generation of reactive oxygen species and other radicals, catalysed by iron ions at the fibre surface, plays an important role in asbestos-induced cytotoxicity and genotoxicity. In this study, structural modification of bovine serum albumin (BSA) adsorbed onto synthetic chrysotile doped with different amounts of Fe has been investigated by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and analytical pyrolysis coupled with gas chromatography-mass spectrometry. FT-IR data evidenced a marked increase in disordered structures like random coil and b-turn of BSA-nanocrystal adduct with 0.52 wt% of Fe doped. The TGA profile of the BSA revealed that its interaction with the synthetic chrysotile surface was strongly affected by the substitution of Fe into the chrysotile structure. The 2,5-diketopiperazine yields, formed upon thermal degradation of the polypeptide chain (pyrolysis-gas chromatography), changed when the BSA was adsorbed on the nanofibres. In general, results suggested that minute amount (less than 1 wt%) of Fe doping in chrysotile affected the protein-nanofibre interactions, supporting the role that this element may play in asbestos toxicity. The catalytic role of iron and the consequent unfolding of protein due to the structural surface modification of nanofibres were also evaluated.

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Different cellular responses evoked by natural and stoichiometric synthetic chrysotile asbestos

Cited by 52 publications

References 33 publications

Inorganic Materials and Living Organisms: Surface Modifications and Fungal Responses to Various Asbestos Forms

Inorganic Materials and Living Organisms: Surface Modifications and Fungal Responses to Various Asbestos Forms

The Iron‐Related Molecular Toxicity Mechanism of Synthetic Asbestos Nanofibres: A Model Study for High‐Aspect‐Ratio Nanoparticles

Adsorption of bovine serum albumin onto synthetic Fe-doped geomimetic chrysotile

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