Playing “Nano -Lego ”: VNPs as Building Blocks for the Construction of Multi -Dimensional Arrays - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 191

The interface between the oil droplet and surrounding water is a liquid-
liquid interface. CPMV or TMV particles, for example, have been self-
assembled at such water-oil interfaces (He

., 2005).
Figure 7.18 shows a monolayer of fluorescent-labeled CPMV particles
self-assembled on perfluorodecalin (oil) droplets in aqueous buffer. CPMV
particles segregated at the oil-water interface, thus stabilizing the oil
droplets. The CPMV monolayer can be cross-linked using glutaraldehyde or
biotinylated CPMV particles in combination with streptavidin (Russell

et al ., 2009; Russell et al

et al .,

2005).

7.7 ARRAYSOFVNPs LAYER-BY-LAYER

Assembly of multi-layered arrays toward the assembly of 3D structures
consisting of nanoparticles or biomolecules can be achieved via layer-by-
layer (LbL) assembly. Multi-layered thin-film assemblies are of growing
interest for the development of miniaturized sensors, reactors, and biochips.
LbL self-assembly methods have been developed, allowing the deposition
of various components in a defined and ordered way. The multi-layered
structure is self-assembled one layer at a time from the surface up. To
interconnect the layers, one can make use of covalent bivalent chemical
linkers, but biospecific interactions and electrostatic interactions are more
commonly employed.

7.7.1 LbL Assembly of VNPs Using Biospeciic Interacions

Multi-layered thin films of CCMV and CPMV have been constructed using the
biotin-streptavidin system (Steinmetz ., 2006).

To achieve this, biotinylated VNPs are immobilized on a solid support;
biotinylated VNPs can be bound on a streptavidin-coated substrate or Cys-
added biotinylated mutants bound on a gold surface. Next, strepatividin
is added. Streptavidin is a tetrameric protein and hence has four binding
sites for biotin. The multivalency of the VNPs and streptavidin allows
interconnection of the VNP layers. A second biotinylated VNP can then be
deposited, followed by a further streptavidin layer, and so on. This process
can be repeated until the desired number of VNP layers is deposited.
In a proof-of-concept study, CPMV particles were covalently labeled with
two different ligands: biotin moieties were displayed allowing self-assembly
via biospecific interaction with streptavidin, and displayed fluorescent
labels served as imaging molecules (Steinmetz

et al ., 2008a, 2006; Suci et al

., 2006). Attachment
of the different functionalities was achieved using the design principles

et al