Ghiazza Mara, Gazzano Elena, Bonelli Barbara, Fenoglio Ivana, Polimeni Manuela, Ghigo Dario, Garrone Edoardo, Fubini Bice
Interdepartmental Center G. Scansetti for Studies on Asbestos and Other Toxic Particulates, Universita degli Studi di Torino, 10125 Torino, Italy.
Chem Res Toxicol. 2009 Jan;22(1):136-45. doi: 10.1021/tx800270g.
To understand the effect of the commercial processing of diatomaceous earths (DEs) on their ultimate surface structure and potential toxicity, we investigated the influence of the industrial processing and the nature of the deposit. Two flux calcined specimens from different deposits, DE/1-FC and DE/2-FC, and the simply calcined sample DE/1-C, from the same deposit as DE/1-FC, were compared in both their bulk and their surface properties. X-ray diffraction (XRD) analysis in a heating chamber revealed the presence of cristobalite in all samples, more abundant on the flux calcined ones. The crystal lattice is probably imperfect, as the alpha-beta transition, visible by XRD in DE/1-FC and DE/2-FC, is not detected by differential scanning calorimetry. Progressive etching with HF solutions suggests that most of the crystalline phase is at the core and not at the outer region of the samples. The combined use of spectroscopic (UV-vis and IR) and calorimetric techniques (heat of adsorption of water as a measure of hydrophilicity) reveals that DE/1-FC and DE/2-FC particles have an external layer of glass, absent in DE/1-C, where iron impurities act as network-forming and sodium ions as modifier species, with few patches of a hydrophobic phase, the latter relatable to a heated pure silica phase. When tested on a macrophage cell line (MH-S) in comparison with appropriate positive and negative controls (an active and an inactive quartz dust, respectively), only DE/1-C exhibited a cell damage and activation similar to that of active quartz (measured by lactate dehydrogenase release, peroxidation of membrane lipids and synthesis of NO). It is likely that the presence of a vitreous phase mitigates or even eliminates the cellular responses of silica in DE.
为了解硅藻土（DEs）的商业加工对其最终表面结构和潜在毒性的影响，我们研究了工业加工和矿床性质的影响。比较了来自不同矿床的两个助熔剂煅烧样品DE/1-FC和DE/2-FC，以及与DE/1-FC来自同一矿床的简单煅烧样品DE/1-C的整体性质和表面性质。在加热室中进行的X射线衍射（XRD）分析表明，所有样品中均存在方石英，在助熔剂煅烧的样品中方石英含量更高。晶格可能不完美，因为在DE/1-FC和DE/2-FC中通过XRD可见的α-β转变未被差示扫描量热法检测到。用氢氟酸溶液进行的逐步蚀刻表明，大部分结晶相位于样品的核心而非外部区域。光谱技术（紫外可见光谱和红外光谱）和量热技术（水的吸附热作为亲水性的度量）的联合使用表明，DE/1-FC和DE/2-FC颗粒有一层玻璃外层，而DE/1-C中没有，在DE/1-C中，铁杂质作为网络形成剂，钠离子作为改性剂，有少量疏水相区域，后者与加热的纯二氧化硅相有关。当与适当的阳性和阴性对照（分别为活性和非活性石英粉尘）相比，在巨噬细胞系（MH-S）上进行测试时，只有DE/1-C表现出与活性石英相似的细胞损伤和激活（通过乳酸脱氢酶释放、膜脂过氧化和一氧化氮合成来测量）。玻璃相的存在可能减轻甚至消除了DE中二氧化硅的细胞反应。
