The inventors have developed novel methods for synthesizing complex silica-based materials, including silica embedded with melanin and silica-based nanostructures and magnetosomes. To generate silica-embedded with melanin, the inventors utilize the R5 peptide, derived from diatoms, to synthesize melanin. This R5-melanin is then used to precipitate silica, resulting in melanin-embedded silica that can be incorporated in hydrogel polymers, bioplastics, fuel cells, and other materials for a wide variety of applications. Importantly, this technology synthesizes silica 90% faster than traditional methods and occurs at ambient temperatures in aqueous conditions.
To form silica-based nanostructures or magnetosomes, the R5 peptide can be fused to fragments of Mms6, an iron-binding protein, or MamC, a magnetosome surface protein. R5-Mms6 precipitates iron oxide to form nanoparticles, which acquire a silica coating when incubated with silicic acid, thereby creating silica-coated magnetic particles. Recombinant expression of R5-MamC in Magnetospirillum magneticum results in formation of R5-coated magnetosomes, which can also precipitate a surface coating layer of silica. These materials can be microwave absorption and electromagnetic interference shielding, for example, in coatings on military stealth vehicles.