Morphology-controlled synthesis of silica materials templated by self-assembled short amphiphilic peptides

Molecular self-assembly has evolved into a robust and powerful bottom-up approach for constructing biomaterials. In this paper, we report the molecular self-assembly of synthetic short amphiphilic peptides (Ac-I3K-NH2, Ac-A(3)K-NH2, and Ac-A(9)K-NH2) and their applications as specific biomineralization templates to investigate mechanisms controlling biosilica morphologies. In pure water, variation of peptide compositions from Ac-I3K-NH2 to Ac-A(3)K-NH2 and Ac-A(9)K-NH2 resulted in altered self-assembly into nanotubes, lamellar stack nanostructures, and nanofibrils, respectively. Addition of phosphate ions did not result in noticeable morphological variation in the self-assembled nanostructures of Ac-I3K-NH2 and Ac-A(3)K-NH2, but favored growth of the Ac-A(9)K-NH2 peptide to form long nanofibrils, suggesting that phosphate ions tune peptide aggregation via different mechanisms. The self-assembled nanomaterials were then utilized as organic templates to direct biosilica formation. Our results indicate that the nature of the peptide/anion complex and external forces were important factors in producing ordered biosilica structures. Because of the exceptional stability of Ac-I3K-NH2 self-assemblies, silica intermediates tended to precipitate directly at the peptide surface, whereas Ac-A(3)K-NH2 and Ac-A(9)K-NH2 self-assemblies mediated re-assembly of large sizes of biosilica particles from twinned crystals. Our findings demonstrate the potential use of self-assembled templates and biomimetic conditions for controlling morphologies of inorganic materials.