Jugdaohsingh Ravin, Brown Andy, Dietzel Martin, Powell Jonathan J
MRC HNR, Elsie Widdowson Laboratory, Cambridge, United Kingdom.
Institute for Materials Research, SPEME, University of Leeds, Leeds, United Kingdom.
PLoS One. 2013 Dec 13;8(12):e84397. doi: 10.1371/journal.pone.0084397. eCollection 2013.
Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2) g(-1) and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates.
尽管铝硅酸盐在我们的自然环境中非常重要且含量丰富，但令人惊讶的是，它们在中性pH值下的形成仍是一个备受争议的问题。通过我们在含铝和硅的稀溶液（pH值约为7）中的实验，我们之前鉴定出了一种对铝离子具有极高亲和力的二氧化硅聚合物（高铝亲和力二氧化硅聚合物，HSP）。在此，进一步的表征表明，HSP是一种直径约为2.4纳米的胶体，平均比表面积约为1000平方米/克，并且它能与转铁蛋白有效竞争结合Al(III)。铝与HSP的结合强烈抑制了其分解，而形成β - 硅钼酸络合物的反应速率常数表明这些含铝纳米颗粒的直径在3.6至4.1纳米之间。同样，对空气干燥的含铝二氧化硅胶体溶液进行的高分辨率显微镜分析揭示了尺寸为3.9±1.3纳米的富含铝的结晶二氧化硅纳米颗粒（ASP），其估计的Al:Si比在2至3之间，这与诸如伊莫石等次生铝硅酸盐的范围相近。因此，高铝亲和力二氧化硅聚合物是一种纳米颗粒，它通过Al(III)离子的高度竞争性结合来引发早期铝硅酸盐的形成。在特定环境中，尤其是在体内，这可能是一种替代机制，用于多羟基Al(III)物种结合单体二氧化硅以形成早期阶段的无毒铝硅酸盐。
