Self-assembled cylindrical particles of wild type and recombinant tobacco mosaic virus (TMV) were used as organic templates for the controlled deposition and organization of Pt, Au, or Ag nanoparticles. Chemical reduction of [PtCl 6 ] 2or [AuCl 4 ]complexes at acidic pH gave rise to the specific decoration of the external surface of wild-type TMV rods with metallic nanoparticles less than 10 nm in size. In contrast, photochemical reduction of Ag(I) salts at pH 7 resulted in nucleation and constrained growth of discrete Ag nanoparticles aligned within the 4 nm-wide internal channel. The number of encapsulated nanoparticles increased when Ag benzoate rather than Ag nitrate was used due to reduced supersaturation associated with the lower Ag/benzoate redox couple, which enhanced the surface-templating effect of the channel wall carboxylates compared with nucleation in solution. Similar experiments using a mutant TMV with reduced negative charge along the central cavity confirmed that glutamic and aspartate acid groups were involved in site-specific deposition. Our results suggest that it should be possible to prepare 1-D arrays for a wide range of inorganic quantum dots by molecular engineering of the internal and external surfaces of self-assembled TMV tubules.

The traditional motivation for integrating biological components into microfabricated devices has been to create biosensors that meld the molecular recognition capabilities of biology with the signal processing capabilities of electronic devices. However, a different motivation is emerging; biological components are being explored to radically change how fabrication is achieved at the micro- and nanoscales. Here we review biofabrication, the use of biological materials for fabrication, and focus on three specific biofabrication approaches: directed assembly, where localized external stimuli are employed to guide assembly; enzymatic assembly, where selective biocatalysts are enlisted to build macromolecular structure; and self-assembly, where information internal to the biological material guides its own assembly. Also reviewed are recent results with the aminopolysaccharide chitosan, a material that offers a combination of properties uniquely suited for biofabrication. In particular, chitosan can be directed to assemble in response to locally applied electrical signals, and the chitosan backbone provides sites that can be employed for the assembly of proteins, nucleic acids, and virus particles.

High area nickel and cobalt surfaces were assembled using modified Tobacco mosaic virus (TMV) templates. Rod-shaped TMV templates (300 x 18 nm) engineered to encode unique cysteine residues were self-assembled onto gold patterned surfaces in a vertically oriented fashion, producing a >10-fold increase in surface area. Electroless deposition of ionic metals onto surface-assembled virus templates produced uniform metal coatings up to 40 nm in thickness. Within a nickel-zinc battery system, the incorporation of virus-assembled electrode surfaces more than doubled the total electrode capacity. When combined, these findings demonstrate that surface-assembled virus templates provide a robust platform for the fabrication of oriented high surface area materials.