Peptides for Silica Precipitation: Amino Acid Sequences for Directing Mineralization

Peptides are promising compounds for use in inorganic or organic-inorganic hybrid syntheses (mineralization) and offer several advantages over proteins. Meanwhile, silica-based nanomaterials have been extensively investigated for many years because of their potential application in a diverse range of technologies, including catalysis, sensing, separation, enzyme immobilization, and gene and drug delivery. Considerable progress has been made over the past decade in understanding the molecular mechanisms underpinning biosilicification and the biomimetic synthesis of patterned nanosilica using peptides.

This mini-review focuses on various peptide sequences, especially short peptide sequences (30 residues or less), for silica mineralization.

We first briefly review early studies on silica mineralization using proteins to provide background information. This is followed by a discussion of promising peptide sequences and attempts to discern the relationship between amino acid sequence, their potential for mineralization, and the properties of the mineral product.

The synthetic control of silica mineralization using engineered proteins, such as recombinant silicateins and silaffins, was inspired by silica biomineralization by natural proteins from organisms (sponges, diatoms, and plants). Concurrently, several papers described the utility of well-structured protein assemblies as templates for silica mineralization. These template-directed syntheses of well-structured silica deposits were first conducted using natural proteins or protein assemblies such as collagen fibers and virus hollow protein tubes. Then we reviewed a selection of short peptides (30 residues or less) that had been successfully used for silica mineralization. Almost all peptides developed to date can be sorted by classification like proteins (synthetic control of silica mineralization or utility of templates for silica mineralization): the first class of peptides is used for peptide-directed synthesis, and the second is used for template-directed synthesis after the peptides have assembled and formed nanostructure such as fibers and tubes. The presented peptides were classified and arranged according to the classification. Additionally, we briefly introduced silica mineralization triggered by the combination of short silica-precipitating peptides and template molecules.

In this mini-review we focused on various peptide sequences, especially short peptide sequences of 30 residues or less, designed for silica mineralization. The peptides have been used both for peptide-directed silica mineralization and for template-directed silica mineralization. The recent advances in peptide-driven mineralization reviewed here suggest that it will soon be possible to completely control the silica mineralization process using peptides. Mineralization systems using peptides will provide researchers with new tools for controlling various inorganic syntheses and the production of organic-inorganic materials for nanobiochemistry and materials chemistry research.