Bone Architecture: Collagen Structure and Calcium/Phosphorus Maps

Abstract

Bone collagen structure in normal and pathological tissues is presented using techniques of thin section transmission electron microscopy and morphometry. In pathological tissue, deviations from normal fine structure are reflected in abnormal arrangements of collagen fibrils and abnormalities in fibril diameter. The relationships between these bone structural changes and the skeletal calcium/phosphorus ratio are discussed. Calcium/phosphorus ratio is measured by X-ray absorptiometry and computed microtomography.

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…12). Thus, biocomposites of biological apatite and molecules of type I collagen are formed (Pasteris et al 2008;Weiner and Wagner 1998;Nightingale and Lewis 1971;Tzaphlidou 2008;Fratzl et al 2004). Some evidences for direct physical bonding between the collagen fibers and apatite crystals in bone were found (Marino and Becker 1967).…”

“…In addition, bones are also involved with blood cell formation, calcium metabolism and act for mineral storage. For a material scientist, bone is a dynamic, highly vascularized solid tissue that is formed from a complicated biocomposite containing both inorganic (Table 3) and bioorganic (chiefly, collagen) compounds, in which nanodimensional crystals of the inorganic phases are dispersed in the meshes of the bioorganic ones (Palmer et al 2008;Nightingale and Lewis 1971;Currey 2002;Rho et al 1998;Tzaphlidou 2008). More than 20 types of collagen have been reported in the human body, among which type I collagen is the most abundant protein and provides much of the structural integrity for connective tissue, particularly in bones, tendons and ligaments.…”

“…Since the bioorganic matrix has control over the size and orientation of CaPO 4 crystals, the latter grow with a specific crystalline orientation-the c-axes of the crystals are roughly parallel to the long axes of the collagen fibrils within which they are deposited (Palmer et al 2008;Grynpas et al 1993;Weiner and Wagner 1998;Currey 2002;Rho et al 1998;Tzaphlidou 2008;Olszta et al 2007). Earlier, it was believed that this process occurred via epitaxial growth mechanism (Marino and Becker 1970).…”

“…In the latter case, thermodynamically, biomineralization might occur at any suitable nucleus. The collagen fibrils have a specific structure with a 67 nm periodicity and 35-40 nm gaps or holes between the ends of the collagen molecules where bone mineral is incorporated in the mineralized fibril (Weiner and Wagner 1998;Weiner et al 1999;Tzaphlidou 2008;Boskey 2007;Glimcher 2006). Such a nucleation within these holes would lead to discrete crystals with a size related to the nucleating cavity in the collagen fibril (Fig.…”

Nanostructured Materials of Calcium Phosphates and Calcium Silicates: Synthesis, Properties and Applications

“…Bone is the composite of biological mineral apatite (~70 wt%) and collagen fibril (~20 wt%). [1,2] Hydroxyapatite (HAP) nanostructures with a plate morphology are combined with collagen into self-assembled complex hierarchical structures. [3][4][5][6] The detailed information on the synthesis, properties and applications of CaP materials has been comprehensively reviewed by Dorozhkin.…”