Hermann Ehrlich

“ A comprehensive understanding of silica-chitin-based sponge skeletons with respect to chemical composition and structure may prove to be a novel model for the biomimetic synthesis also of N-acetyl glucosamine (NAG) and poly-NAG-based composites analogous to well established chitosan-silica hybrid materials [47, 48] with very attractive bioactive properties for applications in biomedicine. ”

“ We believe that chitin is acting as an organic template for silica mineralization in Rossella species in a very similar fashion as in F. occa [17] and E. aspergillum [3] . On the basis of the results presented in this work, we propose a model for the nanostructure of the naturally occurring silica-chitin composite unit, including interaction between poly-N-acetyl glucosaminefragment of the chitin nanofibril and silica nanoparticles, which can be seen in Figure 5. ”

“ RESULTS AND DISCUSSION Most of the glass sponges inhabit soft muddy substrates. One of the strategies of survival under such conditions is the formation of root structures that prevent the body of the animal from sinking into the ground [23] . Due to their preferred deep-sea habitat, the Hexactinellida have been poorly investigated with respect to their general biology [24, 25] and the nature of organic components which build their skeletal
Figure 2: TEM images of silica-organic matrix-based suspension obtained after mechanical disruption of spicules in deionized water (a) . ”

“ Crystallites of organic nature are embedded in amorphous silica (b) .
structures. It was generally accepted that their skeletons are composed of concentric layers of amorphous hydrated silica, containing varying amounts of organic material [26, 27] deposited around a proteinaceous axial filament [28, 29] . The finding of collagen within basal spicules of H. sieboldi [12, 16] and chitin in skeletons of F. occa [17] and in spicules of E. aspergillum [3] , stimulated our attempts to find materials of organic nature in other species of glass sponges. ”

“ In recent years, high-resolution electron microscopy has proved to be an important tool for analysis of the structure of fibrous crystalline polysaccharides, such as cellulose and chitin [36–39] . Therefore, the samples of organic matrix used for FTIR were subsequently submitted to HR-TEM analyses in order to examine the crystalline nature of this material and the plausible additional occurrence of chitin. ”

“ Highly flexible spicules of marine glass sponge Rossella fibulata (a) . Pieces of clean spicules were placed in deionized water and disrupted using magnet stirrer. Visual observations show that the water solution became of a milky color typical for colloidal suspensions of silica (b) . Silica nanoparticles are associated around oriented organic matrix of nanofibrillar nature (c) . ”

“ We detected 19.2 ± 1.5 μg N-acetyl-glucosamine per mg of spicule of R. fibulata. The finding of silica-chitin natural composites as the component of the R. fibulata spicules is in good agreement with results of in vitro experiments on silicification of a βchitin-containing cuttlebone-derived organic matrix as reported by Ogasawara et al. [44] . These authors suggest that silicate ions and silica oligomers preferentially interact with glycopyranose rings exposed at the β-chitin surface, presumably by polar and H-bonding interactions. ”

“ Experiments on biocompatibility of silica-chitin and silicaNAG composites derived in vitro are currently in progress.
4. CONCLUSION4. CONCLUSION Chitin and poly-N-acetyl glucosamine are well investigated materials of biological origin with wide fields of application in biomedicine because of their unique multifunctional engineering mechanical properties and biocompatibility [53–56] . With respect to polysaccharides, including sponge chitin, it is theoretically possible that inorganic Si binds after the macromolecular structure has been formed. ”

“ H. Ehrlich, S. Heinemann, C. Heinemann, et al., “Nanostructiral organization of naturally occuring composites. Part I. Silica-collagen-based biocomposites,” Journal of Nanomaterials. In press.
[2] P. Fratzl, “Biomimetic materials research: what can we really learn from nature’s structural materials?” ”

“ C-6137, respectively, were suspended in 100 mM sodium phosphate buffer at pH 6.0. Digestion was started by mixing 400 μL of the samples and 400 μL of the chitinase-mix. Incubation was performed at 37◦ C and stopped after 114 hours by adding 400 μL of 1% NaOH, followed by boiling for 5 minutes. The effectiveness of the enzymatic degradation was monitored using optical microscopy (Zeis, Axiovert) . The Morgan-Elson assay was used to quantify the N-acetylglucosamin released after chitinase treatment as described previously [22] . ”