Collagen Mineralization and Tissue Repair

The hard tissue(tooth and bone) in vertebrates is formed by the biomineralization processes, which are regulated and controlled by bio-systems. Among them, the mineralized collagen fibril is an essential building block for the construction of biominerals. The mineralized collagen is a hybrid material of nano inorganic mineral (calcium phosphate) and assembled organic molecules(collagen). The advanced nano hierarchical and ordered structure of the mineralized collagen fibrils will endow biological hard tissue with excellent mechanical properties (such as hardness and toughness). The structure feature and mineralization process may inspire new materials fabrications aimed at hard tissue repair. It is important but challenging to reconstruct the ordered organic/inorganic hybrid structures via intrafibrillar mineralization of collagen, and that is the key to the tissue repair. In this review, the same basic questions are discussed including hierarchical structures of bones, the assembled structure of collagen fibrils and the nano-hybrid structure of mineralized collagen fibrils, the interactions between the organic(collagen and non-collagenous proteins) and inorganic counterparts and their interface, the modification of mineralizing interface by the functional molecules, and the control of collagen mineralization and their applications in tissue repair. Some unresolved but urgent issues for collagen mineralization are also discussed, such as the regulation of amorphous precursors for the infiltration into the nano-compartment of collagen fibrils, the control of the mineralization rate and degree, as well as the large scale fabrication of ordered collagen fibrils and their mineralization.