Fabrication of a silica nanocable using hydroxyl-group core-engineered filamentous virus

Biological materials with surface-active proteins can be genetically modified to bind target materials. In particular, filamentous-shaped M13 bacteriophages (M13 phage) are attractive scaffolds for functional nanostructures due to their highly ordered protein-coat surface. This paper demonstrates a simple method for fabricating silica nanocables along a modified M13 phage. The M13 phage was genetically engineered to display the amino acid serine on the surface to provide hydroxyl groups for a sol-gel reaction. This M13 phage mutant offers homogeneous molecular templates for forming silica coated coaxial nanocables. Silica shell formation was confirmed by transmission electron microscopy (TEM) and electron dispersive X-ray (EDX) analysis. The core-shell structures were clearly distinguishable in the TEM analysis, and the synthesized shells were observed by EDX analysis. In addition, we investigated the adsorption properties of M13 phages on the pretreated substrate as a function of concentration. The effect of the relative concentration of M13 phages on the substrate was observed by using atomic force microscopy (AFM). We also fabricated top electrodes on the extremely dense network for measuring electrical properties of the M13 phage. The experimental DC measurement indicated that the wild-type phage has very low electrical conductance, similar to insulating material.