Plant virus capsids are made up of many copies of one or a few types of protein subunits. They assemble to either icosahedral or helical symmetry and are usually arranged around a single-stranded RNA genome. Viral particles can be easily produced in large quantities, either via the infection of plants or by heterologous expression of the subunits using various expression systems, such as Escherichia coli, yeast or insect cells.¹  The high stability of the capsids in combination with their simplicity and the high production yields in plants or heterologous expression systems make plant viruses or virus-like particles (VLPs) an interesting tool for application in bionanotechnology. Since naturally occurring viral particles rarely feature the functional groups desired for chemical modification, they first need to be subjected to genetic and chemical modification of the coat proteins. Subsequently, modified particles can be used e.g. for the encapsulation of foreign material or for incorporation into supramolecular structures.