Hierarchical Architecture of Sponge Spicules: Bio-inspired assembly of multifunctional structures by biocatalytically active and structure-guiding proteins

硅质海绵（Demospongia）和Hexactinellida（玻璃海绵）以及钙质海绵（Calcarea）的分层结构骨骼，具有特殊的光力学特性，已被证明是仿生方法的优秀模型。硅质海绵的生物二氧化硅是由一组独特的酶——硅蛋白形成的，这些酶被证明具有生物催化和结构导向/形成活性。它们骨骼的物种特异性3D结构在基因水平上受到控制，通过硅蛋白和硅蛋白相互作用蛋白的序列基因表达，通过这些蛋白对丝状结构的特定相互作用和组装，以及通过细胞过程。在第一个资助期，已经获得了针状体的无机-有机杂化结构和生物二氧化硅形成机制的基本见解，这被明确地证明是酶作用的。在第二个资助期，新的硅蛋白相互作用物（硅蛋白）被发现并进行了功能表征，使得人们不仅了解了硅蛋白的组装/活性，还了解了细胞外圆柱体状有机支架的形成，指导针状体的纵向和对位生长。此外，首次证明了酶促形成的软质生物二氧化硅到固体二氧化硅棒的协同作用和硬化/老化过程，为海绵生物二氧化硅的仿生/仿生应用开辟了新的途径。在第三阶段，我们将使用这些工具来生成分层结构和多功能纳米材料，应用生物启发分子开关和模拟在自然界海绵中实现的精密生物硅成型工艺。其中，需要研究硅蛋白对碳酸钙/硅蛋白杂化纤维（合成针状体）形成的影响。无机化学和分子生物学小组之间的密切合作将使其能够利用参与生物矿化的海绵蛋白的自组装、结构指导和生物催化能力，以及碳酸钙和金属氧化物的纳米颗粒，用于产生具有新特性组合的仿生纳米结构材料，其机械和光学特性将作为其组成的功能进行检查。

The hierarchically structured skeletons of the siliceous sponges, the Demospongia and the Hexactinellida (glass sponges), and of the calcareous sponges, the Calcarea, with their exceptional opto-mechanical properties have turned out to be excellent models for biomimetic approaches. The biosilica of the siliceous sponges is formed by a unique group of enzymes, the silicateins, that turned out to show both biocatalytic and structure-guiding/forming activity. The species-specific 3D structure of their skeleton is controlled both on gene level, by a sequential gene expression of silicatein and silicatein interacting proteins, and by the specific interaction and assembly of these proteins to filamentous structures, as well as by cellular processes. In the first funding period, fundamental insights have been gained in the inorganic-organic hybrid structure of the spicules and in the mechanism of biosilica formation which was unequivocally proven to occur enzymatically. In the second funding period, new silicatein interactors (silintaphins) have been discovered and functionally characterized, allowing an understanding of the regulation not only of silicatein assembly/activity but also of the formation of the extracellular cylinder-like organic scaffold guiding the longitudinal and appositional growth of the spicules. Moreover, the processes of syneresis and hardening/ageing of the enzymatically formed soft biosilica to solid silica rods have been demonstrated for the first time, opening new avenues for biomimetic/bio-inspired applications of sponge biosilica. In the third period, we will use these tools for the generation of hierarchically structured and multifunctional nanomaterials, applying bio-inspired molecular switches and mimicking precision biosilica molding processes realized in sponges in nature. Among others, the effect of silicatein on the formation of CaCO3/silicatein hybrid fibers (synthetic spicules) shall be studied. The close collaboration between groups from inorganic chemistry and molecular biology shall allow it to exploit the self-assembly, structure-directing and biocatalytic capabilities of the sponge proteins involved in biomineralization, along with nanoparticles of calcium carbonate and metal oxides, for the generation of biomimetic nanostructured materials with new property combinations, whose mechanical and optical properties shall be examined as a function of their composition.