Hierarchical Self-Assembly of Nano-Fibrils in Mineralized Collagen

A designed hierarchical structure was made by self-assembly of nano-fibrils of mineralized collagen resembling extracellular matrix. The collagen fibrils were formed by self-assembly of collagen triple helices. Hydroxyapatite (HA) crystals grew on the surface of these fibrils in such a way that their c-axes were oriented along the longitudinal axes of the fibrils. The mineralized collagen fibrils aligned parallel to each other to form mineralized collagen fibers. For the first time, the new hierarchical self-assembly structure of collagen−hydroxyapatite composite was verified by conventional and high-resolution transmission electron microscopy.