Controlled silica deposition on self-assembled peptide nanostructures via varying molecular structures of short amphiphilic peptides

Abstract

Cationic amphiphilic peptides are highly similar to native silaffins and silicateins for biosilicification in terms of their composition, amphiphilicity, and self-assembling propensity. To understand the relationship between organic molecular structures, molecular self-assembly and silica morphogenesis during biosilicification, we have prepared a series of short self-assembling peptide amphiphiles (I_3–5K, I₄K₂, I_3–4R, and I₄R₂) and investigated their capability to mediate silicification under ambient conditions. I₃K self-assembled into tubular nanofibrils while I₄K_1–2 and I₅K formed solid nanofibrils in aqueous solution with their outer diameters decreasing as the number of hydrophobic or hydrophilic amino acid residues increased. Changes in molecular structure thus altered their self-assembled geometries, and the exposed surfaces and surface lysine densities under different geometries then played different mediating roles in silicification, leading to different silica deposition patterns and final silica nanostructures. The templating capacity was weakened or lost when lysine was replaced by arginine, despite the fact that I_3–4R and I₄R₂ self-assembled into nanofibrils and nanoribbons under similar conditions.