MASTER THESIS Biomimetic potential of sponge ... - IAP/TU Wien

precursor molecules is catalyzed and controlled by silicatein (or its analogue) while the
surface coated with the enzyme (usually a filament consisting of the actual protein) serves as
template (André et al., 2012).
Figure 17 Different polymerization methods inspired by sponge spicules. (André et al., 2011) (Cha et al., 2000)
Biomineralization of sponge spicules (a) has inspired various lines of research. One strategy has been to
polymerize silica by synthetic catalysts that act as a replacement for silicatein. Here, synthetic block
copolypeptides have been used to mineralize silica (b). In attempts rather pertaining to biotechnology,
silicatein has been immobilized on axial filaments and inorganic metal oxides have been polymerized on it at
near-neutral pH and ambient temperature (c). Scale bars are 400 µm (a), 1 µm (b) and 100 nm (c). © by Hannes
Grobe/AWI (a),(Cha et al., 2000) (b), and (André et al., 2011) (c).
Mechanical properties of spicules
Turning to the mechanical properties of spicules of sponges, the distinction between
basal and skeletal elements is relevant. Skeletal elements are rather rigid and convey
hardness and shape to the sponge, while the, usually threadlike, basal spicules are
surprisingly flexible (cf. Figure 6h) and anchor the sponge to the substrate (Kulchin et al.,
2007). Values of micro-hardness and elastic (Young’s) modulus of sponge spicules are
comparable to that of fused silica used in glass fibres (Samsonov & others, 1978). Yet, they
are for more flexible, because these values are not uniform across the radius of basal
spicules and show a pronounced decrease from the centre to the periphery. This is due to
the distinctive layered structure of these spicules with the periodicity of organic/silica
sheaths decreasing from centre to periphery (Kulchin et al., 2008).
Very challenging for the adaption of bio-inspired inspired materials for technology, is the decisive
role of moisture. Johnson and colleagues (2010) investigated mechanical properties of basal
spicules form Euplectella aspergillum in dependence of hydration. They compared the
56