BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 Biomimesis of bone Structure of human bone 2 component model of organic matrix the organic matrix within bone is composed of 2 classes of organic materials Nucleating surface Fig 6.4 Two-component model of the organic matrix o crystals grown out from nucleating surface composed of acidic macromolecules component Composition Water Framework Hydrophobic/cross-linked Matrix structural integrity macromolecules proteins and polysaccharides Acidic Glycoproteins and Nucleating surface for macromolecules hydroxyapatite components in human bones: System Framework macromolecules Acidic macromolecules Bone and dentine Cross-linked type I collagen Glycoproteins Ostoepontin( these rich in Osteonectin Asp and Glu) Chondroitan sulfate Keratin sulfate Tooth enamel Amelogenin Glycoproteins enamelin Organization of organic matrix framework macromolecules o tropocollagen cross-linked at helix ends in staggered arrangement maximizes interfilament cross-links each tropocollagen helix is 280 nm long o gaps between helices 40 nm x 5 nm hole zones Lecture 12-Inorganic biomaterials 9of13BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Biomimesis of bone Structure of human bone 2 component model of organic matrix ƒ the organic matrix within bone is composed of 2 classes of organic materials o crystals grown out from nucleating surface composed of acidic macromolecules component Composition Water solubility Role Framework macromolecules Hydrophobic/cross-linked proteins and polysaccharaides Low Matrix structural integrity Acidic macromolecules Glycoproteins and proteoglycans High Nucleating surface for hydroxyapatite ƒ components in human bones: System Framework macromolecules Acidic macromolecules Bone and dentine Cross-linked type I collagen Glycoproteins: fibrils Ostoepontin (these rich in Osteonectin Asp and Glu) Proteoglycans: Chondroitan sulfate Keratin sulfate Tooth enamel Amelogenin Glycoproteins: enamelin Organization of organic matrix ƒ framework macromolecules o tropocollagen cross-linked at helix ends in staggered arrangement ƒ maximizes interfilament cross-links o each tropocollagen helix is 280 nm long o gaps between helices 40 nm x 5 nm ‘hole zones’ Lecture 12 – Inorganic Biomaterials 9 of 13