Silaffins precursors

In contrast, such approaches have been much more developed with proteins, termed silicateins, that have been extracted from some silicified sponges [38]. The success of these approaches probably originates from the fact that the reactivity of these proteins towards silica precursors differs significantly from the processes occurring in diatoms. Whereas silaffins and poly-amines activate silica formation via electrostatic interactions due to the presence of positively-charged ammonium... 

The acid-catalyzed polycondensation of tetraethoxysilane, a silicic acid precursor, results in the formation of an aggregated silica gel (Figure 1). Con aratively, the three-dimensional structure of die aggregated silica gel was similar to the natural morphologies of the silica particles catalyzed by proteins (9) and polypeptides (12J3J7). Furthermore, e use of external force was demonstrated (21) to control the morphology (e.g. arched, fibrillar) of a silica material catalyzed by a biomimetic silaffin peptide (i.e. a non-modified Sil Ip R5... 

The major differences between biological and biomimetic silica formation mainly lies in precursor concentrations (undersaturated in biosilicification), time required for biosilica deposition, involvement of other molecules (ions, organic molecules, and membranes), and the presence of a confined environment in diatoms. Nonetheless, proteins that direct biomineralization in nature can be used to control the production of nanostructured materials and fecilitate the febrica-tion of new structures in vitro under ambient conditions. Indeed, polycationic silaffins and silicateins isolated from diatoms and sponges, respectively, were shown to generate networlcs of silica nanospheres within seconds when added to a solution of silicic acid. 

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