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Biomineralisation - Apatite-Gelatine-Nanocomposites

Biomimetic apatite-gelatine-nanocomposites are of great interest from the point of view of basic research as well as for different areas of medical applications. This interest is specifically fueled by their close chemical and structural relationships to functional materials in the human body such as bone and teeth. We focus our investigations on fluorapatite-gelatine-nanocomposites. Structures and morphogenetic principles as well as aspects of dental repair applications of such nanocomposites are summarized in a recent review article [1]. With respect to their morphogenetic principles on the µm-scale the fluorapatite-gelatine-nanocomposites (containing ~2.3 wt.-% gelatine) are characterized by a fractal and a fan-like growth mechanism starting from an elongated, hexagonal-prismatic seed and proceeding via growing dumbbell states to finally a slightly notched sphere.

Figure 1. Fractal growth sequence of fluorapatite-gelatine composite aggregates summarized by superposition of SEM images: The initial state is represented by a perfect hexagonal prism (center, red) followed by different dumbbell states (yellow, green) and ending up in a notched sphere. (Print permission kindly provided by “eye of science”, Nicole Ottawa, Oliver Meckes).

As already assumed, for the fractal series the hexagonal-prismatic nanocomposite seed should bear the intrinsic code for its further shape development leading to an outgrowth-scenario for the following generations. It was also assumed, that this scenario has its origin in an intrinsic electric dipole field of the composite seed. The existence of a characteristic electric potential around composite seeds was proved by electron holography. Moreover, this potential was simulated on the basis of the nanocomposite superstructure revealing a qualitatively good agreement with the experimental data [2]. The complexity of the 3D-periodic fluorapatite-gelatine-nanocomposite-superstructure is further increased by an additional pattern consisting of gelatine microfibrils with diameters of around 10 nm [3]. On the base of the dipole model simulations of the formation of the hierarchical fibril pattern within the 3D nanocomposite seed has been successfully performed [4]. Our recent work is especially focused on embryonic states of the fluorapatite-gelatine nanocomposites in order to investigate the shape development at al length scales: From atomistic simulations to pattern formation on the meso-scale [5,6,7].

Figure 2. (Left) Model of a mineralized triple-helical protein representing an idealized dipole containing opposed charges at both ends. The typical length of a building bloc is estimated to be about 300 nm in length and 15 nm in diameter as determined by TEM. (Centre) Parallel assembly of the composite building blocs results in a mesoscopic dipole. (Right) Electric stray field around a hexagonal prismatic seed as evidenced by electron holography.


[1] “Fluorapatite-Gelatine-Nanocomposites: Self-Organized Morphogenesis, Real Structure and Relations to Natural Hard-Materials”
R. Kniep and P. Simon: in Biomineralisation I, (Ed.: K. Naka), Top. Curr. Chem. (2007) 73-125, Springer publisher, Heidelberg.

[2] “Intrinsic Electric Dipole Fields and the Induction of Hierarchical Form Developments in Fluorapatite-Gelatine Nanocomposites: A General Principle for Morphogenesis of Biominerals?”
P. Simon, D. Zahn, H. Lichte, and R. Kniep, Angew. Chem. 118 (2006) 1945-1949; Angew. Chem. Int. Ed. 45 (2006) 1911-1915.

[3] “Biomimetic Development of Complexity: “Hidden“ Hierarchy of Gelatine - Fibrils within 3D-Periodic Fluorapatite-Gelatine–Nanocomposites as Precursor for the Formation of Dumbbell –States”,
R. Kniep and P. Simon, Angew. Chem. 120 (2008) 1427-1431; Angew. Chem. Int. Ed. 47 (2008) 1405-1409.

[4] “Hierarchical pattern of microfibrils in a 3D fluorapatite–gelatine nanocomposite: simulation of a bio-related structure building process”
R. Paparcone, R. Kniep, and J. Brickmann, Phys. Chem. Chem. Phys. 11 (2009) 2186–2194.

[5] “Biomimetic Fluorapatite-Gelatine-Nanocomposites: Pre-Structuring of Gelatine- Matrices by Ion Impregnation and its Effect on Form Development”
H. Tlatlik, P. Simon, A. Kawska, D. Zahn, and R. Kniep, Angew. Chem. 118 (2006) 1939-1944; Angew. Chem. Int. Ed. 45 (2006) 1905-1910.

[6] “The Nucleation Mechanism of Fluorapatite–Collagen Composites: Ion Association and Motif Control by Collagen Proteins”
A. Kawska, O. Hochrein, J. Brickman, R. Kniep, and D. Zahn, Angew. Chem. 120 (2008) 5060-5063; Angew. Chem. Int. Ed. 47 (2008) 4982-4985.

[7] “Embryonic States of Fluorapatite-Gelatine-Composites and Their Intrinsic Electric Field Driven Morphogenesis: The Missing Link on the Way from Molecular Dynamics Simulations to Pattern Formation on the Meso-Scale”
P. Simon, E. Rosseeva, J. Buder, W.G. Carrillo-Cabrera, R. Kniep, Adv. Func. Mater. (2009) submitted.

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