Relationship between surface properties and cellular responses to crystalline silica: studies with heat-treated cristobalite.
A fibrogenic sample of cristobalite dust, CRIS (crystalline silica of mineral origin), was heated to 1300 degrees C (CRIS-1300) to relate induced physicochemical modifications to cytotoxicity. Heating did not affect dust micromorphology and crystallinity, except for limited sintering and decreased surface area of CRIS-1300. Thermal treatments deeply affected surface properties. Electron paramagnetic resonance showed surface radicals progressively annealed by heating, mostly disappearing at >/=800 degrees C. Surface hydrophilicity or hydrophobicity, evaluated with water vapor adsorption, still showed some hydrophilic patches in CRIS-800, but CRIS-1300 was fully hydrophobic. Heating modified the biological activity of cristobalite. Cytotoxicity, tested on proliferating cells of the mouse monocyte macrophage cell line J774, showed that CRIS was cytotoxic and CRIS-800 was still cytotoxic, but CRIS-1300 was substantially inert. Cytotoxicity of CRIS to the rat lung alveolar epithelial cell line, AE6, as measured by colony forming efficiency, was greatly reduced for CRIS-800 and eliminated for CRIS-1300. The rate of lactate dehydrogenase release by rat alveolar macrophages was lowered for CRIS-800, and release was completely inactivated for CRIS-1300. The absence of surface radicals and the onset of hydrophobicity may both account for the loss of cytotoxicity upon heating. Differences observed between CRIS-800 and CRIS-1300, both fully deprived of surface radicals, indicate that hydrophobicity is at least one of the surface properties determining the cytotoxic potential of a dust.
Fubini
B
B
Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Facoltà di Farmacia, Università di Torino, via Pietro Giuria 7, 10125 Turin, Italy. Fubini@silver.ch.unito.it
Zanetti
G
G
Altilia
S
S
Tiozzo
R
R
Lison
D
D
Saffiotti
U
U
D000327:Adsorption; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003114:Colony-Forming Units Assay; D003460:Crystallization; D018360:Crystallography, X-Ray; D004391:Dust; D004578:Electron Spin Resonance Spectroscopy; D004847:Epithelial Cells / Q000187:drug effects; D006358:Hot Temperature; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000187:drug effects; D051379:Mice; D010316:Particle Size; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D012822:Silicon Dioxide / Q000737:chemistry* / Q000633:toxicity*; D013499:Surface Properties; D013816:Thermodynamics
D004391:Dust; D012822:Silicon Dioxide; D007770:L-Lactate Dehydrogenase