Nadine Nassif (Laboratoire Chimie de la Matière Condensée de Paris (LCMCP) Sorbonne Université/CNRS/Collège de France, UMR7574, Paris, France
In biological tissues, a common feature is the presence of dense arrays of biopolymers with ordered geometries at the ultrastructural level. A relationship was established between such 3D arrangements formed by the biological polymers and molecules in liquid crystals (1). This structural analogy between living tissues and liquid crystals suggests similar self-assembly mechanisms in both systems. For Type I collagen (the major structural protein of connective tissue), liquid-crystal self-assembly was shown through the observation of a cholesteric phase in a highly concentrated state in vitro. After a sol/gel transition, collagen fibrils were formed while preserving the cholesteric geometry (2). Recently, the samples were scaled up (from drop to bulk material) using a process based on a continuous injection of collagen to increase the protein concentration. Coupling the liquid-crystalline properties of collagen to a bioinspired hydroxyapatite mineralization process leads to the synthesis of a collagen/apatite composite with high similarities with the bone tissue in terms of composition and structure and more especially the hallmark of trabecular and cortical bones, i.e., the twisted plywood of mineralized collagen fibrils was reproduced (3). We will show that reproducing such bone building-block provides efficient models to study fundamental questions on tissue morphogenesis and, more particularly, bone biomineralization but is also a good starting point for applications in bone tissue engineering through the design of new implantable materials since autologous bone is still considered as the gold standard.
(1) Y. Bouligand, Twisted fibrous arrangements in biological materials and cholesteric mesophases. Tissue Cell. 4, 189–217 (1972).
(2) L. besseau, M.M. Giraud-Guille, Stabilization of fluid cholesteric phases of collagen to ordered gelated matrices. J. Mol. Biol. 251, 197–202 (1995). (3) Y. Wang, T. Azais, M. Robin, A. Vallee, C. Catania, P. Legriel, G. Pehau-Arnaudet, F. Babonneau, M.-M. Giraud-Guille, N. Nassif, The predominant role of collagen in the nucleation, growth, structure and orientation of bone apatite. Nat Mater. 11, 724–733 (2012).
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