Exploitation of plant and archaeal viruses in bionanotechnology.

CPMV (cowpea mosaic virus), a plant virus, is a naturally occurring sphere-like nanoparticle, and is used as a synthon and/or template in bionanoscience. The virions formed by CPMV can be regarded as programmable nanobuilding blocks with a diameter of approximately 30 nm. A range of molecules have been attached to this viral nanoscaffold, yielding stable nanoparticles that display multiple copies of the desired molecule. It has been shown that, in addition to surface amine groups, surface carboxy groups are also addressable, and a procedure has been developed that enables introduction of reactive thiols at the virion surface that avoids virus aggregation. Furthermore, the virions can be functionalized to form electroactive nanoparticles. Methods for the construction of arrays and multilayers, using a layer-by-layer approach, have been established. As proof of concept, for example, CPMV particles have been immobilized on surfaces and arranged in defined layers. Engineered variants of CPMV can be used as templates for mineralization with, for example, silica to give monodisperse robust silica nanoparticles of approximately 32 nm. SIRV2 (Sulfolobus islandicus rod-shaped virus 2), is a robust archaeal virus, resistant to high temperature and low pH. SIRV2 can act as a template for site-selective and spatially controlled chemical modification. Both the ends and the body of the virus, or the ends only, can be chemically addressed; SIRV2 can be regarded as a structurally unique nanobuilding block.