Biocomposites and Mineralized Tissues

Abstract

Bones represent a family of biological materials with complex, hierarchically organized architecture. These diverse mineralized structures are excellently adapted to the variety of mechanical functions and stresses (Weiner et al. 1999; Beniash 2011). According to modern point of view, “bone is specific to vertebrates, and originated as mineralization around the basal membrane of the throat or skin, giving rise to tooth-like structures and protective shields in animals with a soft cartilage-like endoskeleton” (Obradovic-Wagner and Aspenberg 2011). In his excellent monograph, John Long (1995) described the origin and diversity of bone structures which I will now briefly summarize. Bone can be examined as the calcified tissue that supports the skeleton, external or internal, of vertebrates and shows a broad variety of mechanical adaptations at nano- and microscales (Currey 1984, 2002; Weiner and Wagner 1998; Fratzl et al. 2004). A functionally important mechanical property of bones is stiffness, both in the whole element sense and in the material sense (Horton and Summers 2009). Main components of bone include hydroxylapatite (HAP) (as inorganic part), nanofibrillar collagen fibres that support the in vivo development of mineralised bone, and corresponding vascular tissue that supplies blood to the living cell components of bone. Since publication by Kölliker (1859), the presence of cellular and acellular types in the bone of early vertebrates is well established. In spite of that the structures of these bone types are similar, the principal difference between them are the spaces in cellular bone for the osteocytes, which occur throughout this hard tissue.