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Multifunctional Layered Magnetite Composites

 

Professor Dr. Helmut Cölfen, Universität Konstanz; Fachbereich Chemie, AG Physikalische Chemie, Universitätsstraße 10, 78464 Konstanz,

Dr. Damien Faivre, Max-Planck-Institut für Kolloid- und Grenzflächenforschung; Wissenschaftspark Golm, Abteilung Biomaterialien, Am Mühlenberg 1, 14476 Potsdam, 

Dr. Dietmar Schwahn, Forschungszentrum Jülich GmbH; Institute of Complex Systems (ICS), Neutronenstreuung (ICS-1 / JCNS-1), 52425 Jülich,

Professor Dr. Dirk Zahn, Friedrich-Alexander-Universität Erlangen-Nürnberg; Computer-Chemie-Centrum, Nägelsbachstraße 25, 91052 Erlangen,

 

Nature provides many archetypes of highly ordered systems, some of these biomaterials are known for their remarkable mechanical properties1. One particularly interesting class are biominerals which are organic-inorganic hybrid materials and abundant in Nature. Nacre is one of these biominerals combining both stiffness and hardness. The hierarchical structuring of highly organized crystal platelet layers separated by thin layers of organic material is responsible for the fracture resistance of nacre2 (see figure 1).

 

 Figure 1: Schematic representation of a suggested model for nacre formation. A) before mineralization with aragonite and B) after mineralization C) SEM image of nacre with the thin organic matrix layer and the aragonite platelets2

Another amazing biomineral are chiton teeth which are extremely wear resistant through a hybrid design of magnetite nanoparticles embedded in a polysaccharide-protein gel matrix3. Inspired by these materials design concepts, we aim to develop biomimetic composite structures with the fracture resistance of nacre and the hardness and wear resistance of chiton teeth. As a scaffold for the organic-inorganic hybrid material the demineralized organic chitin matrix of nacre is used. The scaffold will be filled with gelatin gel as a mimic for the natural silk hydrogel. In this gel matrix, magnetic nanoparticles (magnetite or maghemite) will be synthesized with and without the control of nucleator peptides derived from studies of proteins responsible for magnetite synthesis in magnetotactic bacteria to take advantage of the genetic control over the magnetite nucleation in these organisms. To co-align the magnetic nanoparticles the synthesis will be performed in a magnetic field. The combination of a nacre-like structure including a mimic of chiton teeth can lead to a fracture resistant as well as wear resistant material with interesting magnetic properties due to the coupling of the magnetic dipoles. The materials are characterized in terms of structure and physical properties. An important technique for structural characterization is small angle neutron scattering. The materials are also simulated to understand molecular origins for their structuration and properties.

 

[1] Weiner, S. & Lowenstam, H.A. On biomineralization, (Oxford University press, Oxford, 1989).

[2] Addadi, L., Joester, D., Nudelman, F. & Weiner, S. Mollusk shell formation: A source of new concepts for understanding biomineralization processes. Chemistry-a European Journal 12, 981-987 (2006).

[3] Weaver, J.C., Wang, Q.Q., Miserez, A., Tantuccio, A., Stromberg, R., Bozhilov, K.N., Maxwell, P., Nay, R., Heier, S.T., DiMasi, E. & Kisailus, D. Analysis of an ultra hard magnetic biomineral in chiton radular teeth. Materials Today 13, 42-52 (2010).