Silicon-Dioxide-Specific Peptides for Biological Nanofabrication: Selecting Aptamers for Target-Specific Ferritin Supramolecule Delivery

Aptamers with 12 amino acid peptides that specifically bind to silicon dioxide (SiO₂) were obtained through the phage-display method. A quartz crystal microbalance (QCM) measurement showed that the peptides bound to the SiO₂ surface quickly, and that the lowest dissociation constant (Kd) was 16 micromolars (μM). The recombinant ferritins, cage-shaped protein mutants that had the aptamers on their outer surface, showed a much higher binding affinity to the SiO₂ surface, and the Kd reached as low as 2.3 nm. The results indicated that multiple aptamers coordinately bound to the SiO₂ surface. It was demonstrated that the aptamers on the outer surface had the ability to selectively deliver the recombinant ferritins with a nanoparticle (NP) to the SiO₂ surface. The NP array made by the recombinant ferritin on the SiO₂ substrate could be used as a nanoetching mask. This technique for making an NP array through ferritins is being applied to other cage-shaped proteins.