"Previous studies from our group and others demonstrated the ability of biomolecules to serve as excellent templates for the fabrication of metal nanowires," Ehud Gazit of Tel Aviv University told nanotechweb.org. "Here, we took the concept one step further into practical application and demonstrated the ability of peptide nanotubes to allow the fabrication of multi-layered coaxial metallic nanowires."
Gazit, Deborah Shalev at the Hebrew University of Jerusalem and colleagues used diphenylalanine peptides as the basis of the self-assembled peptide nanotubes. They discovered that some peptides can self-assemble into nanotubes while researching the formation of amyloid fibrils from proteins, which is a key factor in human diseases such as Alzheimer's, type II diabetes and prion diseases.
The team filled the peptide nanotubes with silver by reducing silver nitrate solution inside the tubes' hollow pores.
To coat the outside of the nanotubes with gold, the researchers employed linker peptides. These contained a diphenylalanine motif for bonding to the peptide nanotube surface and a cysteine residue with a thiol group able to bind to gold nanoparticles. By means of these linker peptides, the team attached 1.4 nm diameter gold nanoparticles to the surface of the nanotubes.
The gold nanoparticles then acted as nucleation sites for electroless deposition of metal ions. In this way, the team created a gold coating around the nanotube that was around 20 nm thick.
The resulting metal-insulator-metal structures should provide advantages for electromagnetic interference shielding.
"Such complex nanoscale bio-inspired structures should allow much more advanced applications in such fields as molecular electronics, (bio)nanosensors and labs-on-a-chip," said Gazit.
The researchers reported their work in Nano Letters.