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Hindawi Publishing Corporation Journal of Nanomaterials Volume 2008, Article ID 623838, 8 pages doi:10.1155/2008/623838

Research Article =Nanostructural Organization of Naturally Occurring Composites—Part I: Silica-Collagen-Based Biocomposites=

Hermann Ehrlich,1 Sascha Heinemann,1Christiane Heinemann,1 Paul Simon,2 Vasily V. Bazhenov,3 Nikolay P. Shapkin,3 René Born,1 Konstantin R. Tabachnick,4 Thomas Hanke,1 and Hartmut Worch,1

1 Max Bergmann Center of Biomaterials and Institute of Materials Science, Dresden University of Technology, 01069 Dresden, Germany 2 Max Planck Institute of Chemical Physics of Solids, 01187 Dresden, Germany 3 Institute of Chemistry and Applied Ecology, Far Eastern National University, 690650 Vladivostok, Russia ''4 P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Nahimovsky pr. 36, 117997 Moscow, Russia''

Correspondence should be addressed to Hermann Ehrlich, hermann.ehrlich@tu-dresden.de

Received 2 November 2007; Accepted 31 December 2007 2008

Recommended by Donglu Shi

Glass sponges, as examples of natural biocomposites, inspire investigations aiming at both a better understanding of biomineralization mechanisms and novel developments in the synthesis of nanostructured biomimetic materials. Diﬀerent representatives of marine glass sponges of the class Hexactinellida (Porifera) are remarkable because of their highly flexible basal anchoring spicules. Therefore, investigations of the biochemical compositions and the micro- and nanostructure of the spicules as examples of naturally structured biomaterials are of fundamental scientific relevance. Here we present a detailed study of the structural and biochemical properties of the basal spicules of the marine glass sponge Monorhaphis chuni. The results show unambiguously that in this glass sponge a fibrillar protein of collagenous nature is the template for the silica mineralization in all silica-containing structural layers of the spicule. The structural similarity and homology of collagens derived from M. chuni spicules to other sponge and vertebrate collagens have been confirmed by us using FTIR, amino acid analysis and mass spectrometric sequencing techniques. We suggest that nanomorphology of silica formed on proteinous structures could be determined as an example of biodirected epitaxial nanodistribution of amorphous silica phase on oriented fibrillar collagen templates. Finally, the present work includes a discussion relating to silica-collagen-based hybrid materials for practical applications as biomaterials.

Copyright © 2008 Hermann Ehrlich et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. INTRODUCTION
Glass sponges (Hexactinellida: Porifera) provide an abundant source of unusual skeleton structures, which could be defined as natural silica-based nanostructured composite materials. They are intriguing research objects because of the hierarchical organization of their spicules from the nanoscale to the macroscale [1–3]. First observations reported by Lévi et al. [4] on silica-based spicules of a Monorhaphis sponge generated great interest because of their combination of properties, namely, toughness combined with stiﬀness, and resilience. This sponge species synthesizes the largest biosilica structures on earth [5]. Pencil-sized rod spicules, a meter or more in length, could be bent into a circle without breaking. When the load was released, the spicule recovered its original shape. When the bending of the spicule rod was compared with that of a synthetically derived pure silica rod, the toughness of the spicule was found to be nearly an order of magnitude higher [2]. Recently, the micromechanical properties of biological silica in the giant anchor spicule of Monorhaphis chuni were reported on [6]. Nanoidentation showed a considerably reduced stiﬀness of the spicule compared to technical quartz glass with diﬀerent degrees of hydration. Moreover, stiﬀness and hardness were shown to oscillate as a result of the laminate structure of the spicules. Raman spectroscopic imaging showed that the organic layers are protein-rich and that there is an OH-enrichment in silica near the central axial filament of the spicule. Smallangle X-ray scattering revealed the presence of nanospheres with a diameter of only 2.8 nm as the basic unit of silica.