Britain scientists have produced a 3D nanoscale reconstruction of the mineral structure of bone and explained how it could own an adequate toughness and strength in a study published on Thursday in the journal Science.
The properties of bone are attributed to its hierarchical organization, where small elements form larger structures, but the nanoscale organization and relationship between bone's principle components, namely mineral and protein, have not been fully understood previously.
Using advanced 3D nanoscale imaging of the mineral in human bone, the research teams from the University of York and Imperial College London have shown that the mineral crystals of bone have a hierarchical structure integrated into the larger-scale make-up of the skeleton.
They found that the principal building blocks of mineral at the nanometer scale were curved needle-shaped nanocrystals that formed larger twisted platelets that resembled propeller blades.
According to the researchers, the blades continuously merge and split throughout the protein phase of bone. The interweaving mineral and protein form continuous networks to provide the strength essential for functional bones.
Roland Kroger, the paper's lead author and associate professor with the University of York's Department of Physics, said: "Bone is an intriguing composite of essentially two materials, the flexible protein collagen and the hard mineral called apatite."
"The combination of the two materials in a hierarchical manner provides bone with mechanical properties that are superior to those of its individual components alone and we find that there are 12 levels of hierarchy in bone," said Kroger.
Also, they found that the mineral crystals are curved, the protein strands (collagen) are braided, the mineralized collagen fibrils twist, and the entire bones themselves have a twist, such as those seen in the curving shape of a rib.