Hermann Ehrlich

“ Correspondingly, this kind of collagen fibril orientation could explain why sponge spicules exhibit specific flexibility and can be bent even to a circle as reported previously [2, 4, 21] . From this point of view, basal spicules of Monorhaphis sponges could be also defined as natural plywood-like silica-ceramics organized similarly to the crossed-lamellar layers of seashells [33] . Thus, we suggest that the matrix of the M. chuni anchoring spicule is silificated fibrillar collagen rather than collagen-containing silica which is the reason for their remarkable mechanical flexibility. ”

“ Therefore, it is not unreasonable to hypothesize that silicateins are proteins responsible for the reconstruction of collagen to form templates necessary for the subsequent silica formation. According to a dynamic model proposed by Müller and his team [5] , collagen guides the silicatein (-related) protein/lectin associates concentrically along the spicules of M. chuni. On the basis of the results presented in this paper, we propose a model for the structure of the spicules of Monorhaphis sponges, including micro- and nanoaspects, which can be seen in Figure 5. ”

“ 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. ”

“ The procedure of alkali slow etching opens the possibility to observe the forms of collagen fibrils located within silica layers of spicules and their distribution. The results obtained by SEM observations of the desilicified spicular layers provide strong evidence that collagen fibrils’ orientation within M. chuni spicules possesses twisted plywood architecture (Figures 3 (c) and 3 (d) ) . The twisted plywood or helicoidal structure of collagen fibrils is well-described by Giraud-Guille [30] for bothin vivo and in vitro [31] systems. ”

“ The axial canal of M. chuni possesses a characteristic quadratic opening (c) and contains oriented bundles of unsilicified collagenous nanofibrils. The base material of the walls of the axial canal and concentric layers distributed above it consists of silicified collagen fibrils with a twisted plywood orientation. This kind of fibrillar architecture could be responsible for the remarkable micromechanical properties of the spicule as a biocomposite.
similar to that reported for lamellar bone and thus could also confirm the Girauld-Guille model in the case of biosilification in vivo. ”

“ Of course, the materials science aspects of glass sponges can be studied by model systems, and utilized for biomimetic engineering. However, we cannot mimic nature with a view to designing novel biomaterials without knowledge of the nature and origin of the organic nanostructured matrices of corresponding natural biocomposites which are present in these sponges. ”

“ Corresponding electrophoretic gels stained with Coomassie were used for the determination of the aminoacid sequence by a mass spectrometric sequencing technique as described above. We excised two main bands and digested protein material in-gel with trypsin to obtain tryptic peptide mixtures
Figure 2: SEM images of multilayer constructed M. chuni spicule (a) treated with alkali solution which provides strong evidence that the multifibrillar organic matrix is the template for silica mineralization (b) – (e) . ”

“ 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. ”

“ In order to exploit the mechanisms for the synthesis of advanced materials and devices, an investigation of the nanoscopic structure of the three-dimensional networks of these remarkable biomaterials needs to be performed [35–38] . ”

“ Nature Materials, vol. 6, no. 6, pp. 434–439, 2007.
[38] P. Fratzl, “Biomimetic materials research: what can we really learn from nature’s structural materials?” Journal of the Royal Society Interface, vol. ”