M. Fricke, D. Volkmer: Crystallization of Calcium Carbonate Beneath Insoluble Monolayers: Suitable Models of Mineral-Matrix Interactions in Biomineralization? H. Imai: Self-Organized Formation of Hierarchical Structures R. Kniep, P. Simon: Fluorapatite-Gelatine-Nanocomposites: Self-Organized Morphogenesis, Real Structure and Relations to Natural Hard-Materials K. Sato: Inorganic-Organic Interfacial Interactions in Hydroxyapatite Mineralization Processes C.K. Carney, S.R. Harry, S.l. Sewell, D.W. Wright: Detoxification Biominerals
Fluorapatite-Gelatine-Nanocomposites: Self-OrganizedMorphogenesis, Real Structure and Relations to Natural Hard Materials (p. 74-75)
Abstract The biomimetic system fiuorapatite-gelatine (in aqueous solutions) is perfectly suited for the study of biomimetic steps closely related to steps in osteo- and dentinogenesis. Although representing a relatively low level of complexity, the biomimetic system still includes all aspects of complexity, such as metastability, self assembly, self-similarity, fractals, pattern-formation, hierarchy, and others. The present review is focused on the morphogenesis and real structure of fiuorapatite-gelatine-nanocomposites and is structured in a sequence from macroscopic/bulk-properties to mesoscopic and finally microscopic observations, in part also supported by atomistic simulations. The field encompasses a large variety of components reaching from basic science to applications. Keywords Applications · Atomistic simulations · Electrical dipole fields · Fluorapatite · Gelatine · Morphogenesis · Nanocomposites
The biomimetic system fiuorapatite-gelatine bears strong resemblance to the biosystem hydroxyapatite (HAP)-collagen which plays a decisive role in the human body (vertebrates in general) as functional material in the form of bone [1, 2] and teeth [3, 4]. In the bio-systems, the hierarchical and self-similar organization of nanocomposite structures is of prominent relevance [5?8], with HAP-protein (collagen) nanocomposite structures dominated by a close orientational relationship between the triple-helical collagen molecules (arranged in the form of fibrils) and the HAP nanocrystals which .rst nucleate in the gaps between neighboring protein molecules. In these arrangements, the crystallographic c-axes of theHAP nanocrystals are oriented parallel to the longitudinal direction of the fibrils [9, 10].
As the development of bone and teeth proceeds during processes of high complexity involving metabolisms and cell activities of living system, it was a consistent decision to clearly reduce the level of complexity by restricting the investigations to water-soluble gelatine (denatured collagen) and aqueous solutions of the appropriate ions needed for the formation of apatite. The biomineralization process is then mimicked by a double diffusion system in which the ions migrate into a gelatine gel from opposite reservoirs containing solutions of calcium and phosphate/fiuoride, respectively. The mobility of the protein (gelatine) in the gel thereby eases rearrangements of the protein fibers during processes of self-organization.
1.1 Basic Idea and Conception
The chemical system under consideration raised great hopes as being representative of a materials combination that had been optimized during the processes of evolution, and which would allow us to gain deeper insight into the general principles of biomineralization (the formation of inorganic/organic nanocomposites). This task is a real challenge and has to be tackled on all length scales accessible by various methods of investigation. Therefore, the present review is structured in a sequence from macroscopic/bulk-properties to mesoscopic and finally microscopic observations. We are still far away from a perfect understanding of all the experimental indications obtained so far, but it has already become clear that the first steps in this direction have been taken showing promising future trends. The field encompasses all the components from basic science to applications. With respect to materials properties and applications an increasing interest is clearly reflected by the presently increasing number of publications dealing with apatite-gelatine composites [11?14].