Scientists from Max Planck Institute (Germany) and the ESRF have just discovered the way deformation at the nanoscale takes place in a bone by studying it with the synchrotron X-rays. This study explains the enor-mous stability and deformability of bones. The hierarchical structure of bones makes them able to sustain large strains without breaking, de-spite being made of essentially rigid units at the molecular level. The re-sults are published this week in the PNAS online edition.
A bone is made up of two different elements: half of it is a stretchable fibrous protein called collagen and the other half a brittle mineral phase called apatite. These com-ponents make this biomineralized tissue highly strong and tough. at the same time, In order to understand how this construction is achieved and functions, scientists from the Max Planck Institute of Colloids and Interfaces in Potsdam (Germany) came to the ESRF. Using X-rays they were able to see for the first time the simultaneous re-arrangement of organic and inorganic components at a micro and nanoscale level under tensile stress.
The scientists realised that when strain/pressure is applied to a bone, this is ab-sorbed by soft layers at successively lower length scales, and less than a fifth of the strain is actually noticed in the mineral phase. The soft structures form a single rigid unit at the next level and so on, enabling the tissue to sustain large strains. This is why the brittle apatite remains shielded from excessive loads and does not break.
The results also showed that the mineral crystallites are nonetheless very strong, ca-pable of carrying more than 2 3 times the fracture load of bulk apatite. Their small size preserves them from large cracks. This is the first experimental evidence for this effect in biomaterials small particles resist failure better.
Scientists carried out experiments on ID2 beamline at the ESRF. They
tracked the molecular and supramo
Contact: Montserrat Capellas
European Synchrotron Radiation Facility