Playing “Nano -Lego ”: VNPs as Building Blocks for the Construction of Multi -Dimensional Arrays - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 192

described in Chapter 4. Different color-labeled sets of biotinylated CPMV
particles were added sequentially and an array was built from the surface
up (Steinmetz

., 2006). Fluorescence microscopic analysis allowed
differentiation between a mixed monolayer

et al

versus a bilayer structure (Fig.

7.19) (Steinmetz et al ., 2006).

Figure 7.19 Bilayers and a mixed monolayer of biotinylated (bio) and fluorescent-

labeled CPMV particles on Au slides imaged via fluorescence microscopy (left), and
diagrammatic representation of layer structures (right). The green and red flags
show the AlexaFluor dyes AF488 and AF568, respectively. The black cross depicts
streptavidin (SAv); the gray cross shows a thiol-modified SAv. The scale bar is 10 m.

(a) Bilayer of CPMV-BIO-AF488 and CPMV-BIO-AF568, CPMV-BIO-AF488 in the first
and CPMV-BIO-AF568 in the second layer; merge shows the overlaid images from
the first and second layers. (b) Bilayer of CPMV-BIO-AF568 and CPMV-BIO-AF488.
(c) Mixed monolayer of CPMV-BIO-AF488 and CPMV-BIO-AF568. Reproduced with
permission from Steinmetz, N. F., Calder, G., Lomonossoff, G. P., and Evans, D. J. (2006)
Plant viral capsids as nanobuilding blocks: construction of arrays on solid supports,
Langmuir

µ

, 22 (24), 10032-10037.

In a follow-up study, the mechanical properties of such arrays were
investigated (Steinmetz

., 2008a). Multi-layered build-up of various
CPMV building blocks modified with varying densities (30 labels versus

et al

200 labels) of biotin molecules attached via longer (3.50 nm) and shorter
linkers (2.24 nm) was investigated. Arrays were fabricated by alternating
deposition of streptavidin and biotinylated CPMV particles. Biophysical
measurements showed that the mode of multi-layer assembly was different
for each array fabricated. The general trend was that a more regular and
densely packed, strongly interlinked array was assembled when CPMV
particles displaying a high number of biotin labels attached via the longer
linker were used. In stark contrast were the mechanical properties of arrays
formed with CPMV particles displaying a low number of biotins attached
via the shorter linker. The formation of a viscoelastic array with less dense
particle packaging was implied (Steinmetz et al ., 2008a). The observation