SIBLING Protein Induced Biomineralization

SIBLING Protein Induced Biomineralization

Native bone tissue is composed of a matrix of collagen, non-collagenous proteins, and mineral, mostly hydroxyapatite (HAP). Bone sialoprotein (BSP), osteopontin (OPN), and dentin phosphoprotein (DPP) are all members of the SIBLING (small integrin-binding ligand, N-linked glycoprotein) family of proteins, which are primarily found in mineralized tissues. In this work, the mineralization induction capabilities of BSP, OPN, and DPP are explored. Radiolabeled adsorption isotherms were constructed for BSP, OPN, and DPP on a biomimetic collagen substrate.  The results showed that BSP exhibited the highest binding capacity for collagen, followed by DPP, and then OPN. The adsorption isotherms were then used to study the effects of equal amounts of adsorbed proteins on a collagen substrate with respect to HAP formation and morphology. Mineralization studies were performed, and the adsorption isotherms were used to determine solution concentrations that would result in equal amounts of adsorbed protein for each of the three proteins. Substrates were placed in simulated body fluid for 5h, 10h, and 24h in an incubation chamber at 37 ^oC. Photochemical assays were performed on demineralized substrates to determine a Ca/P ratio for minerals formed with each of the proteins used at all time points considered. Additionally, SEM images were taken of the substrates to provide a qualitative comparison of mineral surface coverage at each time point.