Toward a better understanding of mineral microstructure in bony tissues

Bone is a multifunctional composite of type-I collagen fibrils and mineral crystallites organized into a complex hierarchical structure. Microstructural features of the mineral constituents in selected bony tissues, including bovine femur and armadillo and turtle osteoderms were characterized by optical and scanning electron microscopy before and after complete deproteinization. Minerals in the three types of bony tissues retained structural integrity after completely removing protein constituents and showed similar structural features at the nanoscale. High-resolution scanning electron microscopic images showed minerals formed fibril-like structures, aligned in a coherent manner along the orientation of collagen fibrils with a 67-nm periodicity. Organized porous structures at varying hierarchical levels were well preserved after complete deproteinization. The authors demonstrate that bone architecture, from the nano- to macro-scale can be better visualized and analyzed after deproteinization. A bony tissue with unique microstructure is reported for the armadillo osteoderm. This comparative study provides better understanding of the structure of the mineral constituents in bony tissues that could further lead to novel design of bioinspired composites.