Shaping highly regular glass architectures: A lesson from nature

Abstract

Protein crystal branching guides the morphogenesis of glass spicules in marine sponges from the class Demospongiae.

Modern scaffolding strategies based on naturally pre-fabricated 3D biomaterials of poriferan origin

“…The fusion of properties of all of these levels ensures outstanding energy dissipation and resistance to mechanical strain [12][13][14][15][16]. Surprisingly, fabrication of such hierarchical complex glass structures still seems to be far beyond the reach of current human technology [17]. Numerous studies of glass sponges skeletons suggest that the unique fracture toughness results from the spicules cylindrical layered architecture.…”

“…Over the last decades numerous research groups analyzed the organic constituents involved in spiculogenesis and supporting formation of sophisticated glass sponge constructs. According to the present state of art, four different organic templates that may be involved in biosilicification in glass sponges were isolated and proposed: silicateins [17,23], glassin [24], collagen [25] and chitin [26,27]. The silicatein-and glassin-based hypotheses are in conflict with the proposed role of collagen and chitin as alternative templates in spicule formation in glass sponges (for details please see [7]) and became a serious bone of contention between various research groups.…”

Natural hybrid silica/protein superstructure at atomic resolution

“…Astonishingly, being composed of an inherently disordered amorphous material, these skeletal elements exhibit a variety of highly regular species-specific branched morphologies and are considered a paradigm of symmetry in biomineralized systems ( 9 ). A recent study revealed that this order is realized with the assistance of axial filaments that pass through the center of every branch in every spicule and direct silica deposition ( 10 ). The filaments in demosponges were demonstrated to be perfect slender protein crystals, and their branching on well-defined crystallographic planes of that crystal was shown to be responsible for the high spatial regularity and symmetry of the spicules.…”

“…In contrast, the crystalline assembly of silicatein units in vivo, inside the axial filaments of demosponges, such as T. aurantium , is well recorded by a number of recent X-ray diffraction and transmission electron microscopy studies ( 10 , 24 – 26 ). The marine sponge T. aurantium ( Fig.…”

“…1 D ). Silicateins in the filaments of these glass needles were shown to be packed in a perfect hexagonal superstructure with lattice parameters of a = 5.95 ± 0.01 nm and c = 11.89 ± 0.01 nm, with the c -axis oriented parallel to the long axis of the spicule ( 10 ). Yet again, whereas a number of contradictory models describing the mechanism of silicatein self-assembly were previously proposed, the lack of its tertiary structure limits our understanding of silicatein crystallization, its assembly into a filament, spicule morphogenesis, and, finally, demosponge skeletogenesis ( 27 , 28 ).…”