Nanoscale chemical tomography of buried organic- inorganic interfaces in the chiton tooth

摘要

Biological organisms possess an unparalleled ability to control the structure and properties of mineralized tissues. They are able, for example, to guide the formation of smoothly curving single crystals or tough, lightweight, self-repairing skeletal elements1. In many biominerals, an organic matrix interacts with the mineral as it forms, controls its morphology and polymorph, and is occluded during mineralization. The remarkable functional properties of the resulting composites-such as outstanding fracture toughness and wear resistance-can be attributed to buried organic-inorganic interfaces at multiple hierarchical levels. Analysing and control-ling such interfaces at the nanometre length scale is critical also in emerging organic electronic and photovoltaic hybrid materials6. However, elucidating the structural and chemical complexity of buried organic-inorganic interfaces presents a challenge to state-of-the-art imaging techniques. Here we show that pulsed-laser atom-probe tomography reveals three-dimensional chemical maps of organic fibres with a diameter of 5-10 nm in the surrounding nano-crystalline magnetite (Fe_3O_4) mineral in the tooth of a marine mollusc, the chiton Chaetopleura apiculata. Remarkably, most fibres co-localize with either sodium or magnesium. Furthermore, clustering of these cations in the fibre indicates a structural level of hierarchy previously undetected. Our results demonstrate that in the chiton tooth, individual organic fibres have different chemical compositions, and therefore probably different functional roles in controlling fibre formation and matrix-mineral interactions. Atom-probe tomography is able to detect this chemical/structural heterogeneity by virtue of its high three-dimensional spatial reso-lution and sensitivity across the periodic table. We anticipate that the quantitative analysis and visualization of nanometre-scale inter-faces by laser-pulsed atom-probe tomography will contribute greatly to our understanding not only of biominerals (such as bone, dentine and enamel), but also of synthetic organic-inorganic composites.%牙齿和骨头等很多生物矿化组织是无机物和有rn机物的混合物，其性质由它们难解的内部结构rn决定。现在，Lyle Gordorl和Derk，Joester介绍rn了怎样利用“脉冲激光原子探针断层扫描术”rn(APT)(这是在冶金和半导体研究中的一种成rn熟方法)来阐明这种生物材料及其人工合成的rn类似物质的内部结构和化学复杂性。该研究rn中所用的材料是来自一种被称为“Eastemrnbeaded chiton”的海洋软体动物的一颗牙齿。rn所获得的高分辨率3D化学图显示了牙齿内的rn不同有机纤维，它们有不同的组成，因此在控rn制有机基质与无机矿物相之间的相互作用中很rn可能也有不同的功能。除了揭示自然出现的物rn质的性质外，APT方法在该领域的这种应用也rn应当能够为设计从生物得到启发的、有医学和rn工业用途的复合材料提供有用数据。