Credit: © ACS

Metallic nanowires are grown on a template that determines the dimensions of the wire. Researchers in Israel have now shown that both the inside and outside surfaces of hollow peptide nanotubes can be used as a scaffold to make coaxial nanowires.

Ehud Gazit and colleagues1 at Tel Aviv University and the Hebrew University of Jerusalem begin by allowing small dipeptide building blocks to self-assemble into robust, micrometre-long nanotubes. When placed into a solution of a silver salt, the channel inside each nanotube fills with silver ions. As Gazit has demonstrated previously, these ions can then be cast into a continuous nanowire when the system is chemically reduced with citric acid — a reaction in which the addition of electrons lowers the oxidation state of the metal to zero.

The outer surface of the nanotubes can be modified by attaching short linker peptides. These molecules have thiol groups at their ends to which gold nanoparticles are anchored. These surface-bound particles serve as nucleation sites for the assembly and subsequent reduction of gold ions from solution, which results in a thin gold plating along the length of the nanotubes.

This research not only offers an insight into the self-assembly of peptide nanotubes, but also demonstrates the utility of these structures for the construction of multi-component organic-inorganic hybrid nanostructures.