Nano-Deformation Mechanisms in Bone Collagen Fibrils

Orateur : Baptiste DEPALLE (Wellcome Trust/MIT Research Fellow, Department of Materials, Imperial College, London, UK)

The remarkable mechanical properties of bone are dependent upon its complex hierarchical structure made up of an organic matrix, filled with a mineral phase and water. However, the interactions between mineral and organic matter that endow bone with its toughness at the nanoscale have thus far been elusive. Identifying these mechanisms is critical to unlocking the nanoscale underpinning of diseases such as osteoporosis and to developing guidelines for engineering of bone and partially mineralized tissues. We explore the intricate relationship between the nanostructure of bone collagen fibrils and their mechanical behavior using coarse-grained molecular dynamics. Here, we focus specifically on the role of enzymatic cross-links and intrafibrillar mineralization in a single collagen fibril. These represent two different ways to improve intermolecular interaction and improve the fibrils mechanics by taking advantage of the full mechanical potential of every collagen molecule in the structure. Cross-linked and mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy which include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage and crystal dissociation. By multiplying their sources of energy dissipation and deformation mechanisms, collagen fibrils can reach impressive strength and toughness and give bone its remarkable mechanical properties.

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