Probing the mechanical response of bone on sub-10-nm length scales shows that minerals are essential for resisting fracture
The mechanical properties of our bones have to cover all types of impact. This ranges from low-stress activities like walking, which require elasticity, to sudden jolts that stress our heels and back. Understanding the mechanisms naturally present in bone that prevent fracture will help treat problems resulting from age and disease.
With this in mind, Christine Ortiz and colleagues1 of the Massachusetts Institute of Technology in the USA are exploring the nanostructural origins of bone strength. They suggest that calcium-based minerals coating bone fibres provide frictional resistance to cracks and failure. A combination of nanoindentation — a probe that pushes into a material under the pressure of a sharp tip — and atomic force microscopy imaging are used to study how bone responds to compressive forces on sub-10-nm length scales. Compared with demineralised bone, normal bone shows a greater resistance to stress.
Nature appears to mirror the group’s experimental findings. Tendons, which respond to pulling type forces, contain no minerals. On the other hand, minerals make up nearly the entire weight of whale bones, which must sustain substantial compression forces.
Tai, K. Ulm, F.-J. & Ortiz, C. Nano Lett. (2006). 10.1021/nl061877k