Shen Z, Bosbach D, Hochella M F, Bish D L, Williams M G, Dodson R F, Aust A E
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
Chem Res Toxicol. 2000 Sep;13(9):913-21. doi: 10.1021/tx000025b.
Recent studies have shown that iron is an important factor in the chemical activity of asbestos and may play a key role in its biological effects. The most carcinogenic forms of asbestos, crocidolite and amosite, contain up to 27% iron by weight as part of their crystal structure. These minerals can acquire more iron after being inhaled, thereby forming asbestos bodies. Reported here is a method for depositing iron on asbestos fibers in vitro which produced iron deposits of the same form as observed on asbestos bodies removed from human lungs. Crocidolite and amosite were incubated in either FeCl(2) or FeCl(3) solutions for 2 h. To assess the effect of longer-term binding, crocidolite was incubated in FeCl(2) or FeCl(3) and amosite in FeCl(3) for 14 days. The amount of iron bound by the fibers was determined by measuring the amount remaining in the incubation solution using an iron assay with the chelator ferrozine. After iron loading had been carried out, the fibers were also examined for the presence of an increased amount of surface iron using X-ray photoelectron spectroscopy (XPS). XPS analysis showed an increased amount of surface iron on both Fe(II)- and Fe(III)-loaded crocidolite and only on Fe(III)-loaded amosite. In addition, atomic force microscopy revealed that the topography of amosite, incubated in 1 mM FeCl(3) solutions for 2 h, was very rough compared with that of the untreated fibers, further evidence of Fe(III) accumulation on the fiber surfaces. Analysis of long-term Fe(III)-loaded crocidolite and amosite using X-ray diffraction (XRD) suggested that ferrihydrite, a poorly crystallized hydrous ferric iron oxide, had formed. XRD also showed that ferrihydrite was present in amosite-core asbestos bodies taken from human lung. Auger electron spectroscopy (AES) confirmed that Fe and O were the only constituent elements present on the surface of the asbestos bodies, although H cannot be detected by AES and is presumably also present. Taken together for all samples, the data reported here suggest that Fe(II) binding may result from ion exchange, possibly with Na, on the fiber surfaces, whereas Fe(III) binding forms ferrihydrite on the fibers under the conditions used in this study. Therefore, fibers carefully loaded with Fe(III) in vitro may be a particularly appropriate and useful model for the study of chemical characteristics associated with asbestos bodies and their potential for interactions in a biosystem.
最近的研究表明，铁是石棉化学活性的一个重要因素，可能在其生物学效应中起关键作用。石棉最具致癌性的形式，青石棉和铁石棉，在其晶体结构中含有高达27%（重量）的铁。这些矿物在吸入后可以获取更多的铁，从而形成石棉小体。本文报道了一种在体外将铁沉积在石棉纤维上的方法，该方法产生的铁沉积物与从人肺中取出的石棉小体上观察到的形式相同。将青石棉和铁石棉在FeCl₂或FeCl₃溶液中孵育2小时。为了评估长期结合的效果，将青石棉在FeCl₂或FeCl₃中孵育，铁石棉在FeCl₃中孵育14天。通过使用与螯合剂亚铁嗪的铁测定法测量孵育溶液中剩余的铁量，来确定纤维结合的铁量。在进行铁负载后，还使用X射线光电子能谱（XPS）检查纤维表面是否存在增加的表面铁。XPS分析表明，负载Fe(II)和Fe(III)的青石棉表面铁含量均增加，而仅负载Fe(III)的铁石棉表面铁含量增加。此外，原子力显微镜显示，在1 mM FeCl₃溶液中孵育2小时的铁石棉的形貌与未处理的纤维相比非常粗糙，这进一步证明了Fe(III)在纤维表面的积累。使用X射线衍射（XRD）对长期负载Fe(III)的青石棉和铁石棉进行分析表明，形成了水铁矿，一种结晶度差的含水氧化铁。XRD还表明，水铁矿存在于从人肺中取出的铁石棉核心石棉小体中。俄歇电子能谱（AES）证实，Fe和O是石棉小体表面仅有的组成元素，尽管AES无法检测到H，但推测H也存在。综合所有样品的数据，本文报道的数据表明，Fe(II)的结合可能是由于纤维表面的离子交换，可能是与Na交换，而在本研究使用的条件下，Fe(III)的结合在纤维上形成水铁矿。因此，在体外小心负载Fe(III)的纤维可能是研究与石棉小体相关的化学特性及其在生物系统中相互作用潜力的特别合适和有用的模型。
