Biology Reference
In-Depth Information
that the mechanical properties of the CPMV arrays can be tightly tuned
by adjusting spacer length and density is interesting and important. The
judicious use of appropriate linkers will allow the design of thin films with
the desired needs and properties, for example, rigid and densely packed
versus viscoelastic and less densely packed.
The biotin-streptavidin system in combination with the hexa-His-Ni-
NTA system has also been used to construct hybrid arrays consisting of
VNPs and inorganic materials. Quantum dots (QDs) have been specifically
captured onto an immobilized CPMV layer (Medintz
., 2005). The CPMV
layer offers a large surface area compared with a flat surface. In addition,
the CPMV layer offers symmetrically arranged anchoring groups. It was
estimated that when a close-packed layer of CPMV was used to capture QDs,
a 40% increase in QD density could be achieved. An enhanced fluorescence
signal was indeed observed comparing quantum dots captured on a CPMV
surface versus a flat surface (Medintz
et al
., 2005).
The utility of such a hybrid CPMV system for data storage has been
demonstrated (Portney
et al
., 2007). CPMV particles decorated with QDs
were immobilized and embedded in a polyvinyl alcohol (PVA) matrix. The
PVA matrix containing the hybrid VNPs was sandwiched between two
electrodes and an electric field was applied. The current-voltage curves
showed several multi-stable switching states. This implies that these
materials could indeed find applications in non-volatile memory devices
(non-volatile describes a storage device that stores information even when
it is not powered) (Portney
et al
., 2007).
These techniques have been extended and iron oxide nanoparticles have
also been captured on CPMV monolayers by making use of covalent chemical
linkages. Potential applications of CPMV-iron oxide nanoparticle hybrids lie
in the field of bioimaging, such as MRI (see Chapter 8) (Martinez-Morales
et al
et
al
., 2008) .
7.7.2LbLAssemblyUsingElectrostaicInteracions
Multi-layered arrays consisting of polyelectrolytes and VNPs can be fabricated
via electrostatic interactions. Interestingly, the behavior of icosahedrons
versus rods in polyelectrolyte multilayers was found to be different.
Multi-layered arrays of alternating charged polyelectrolytes and charged
icosahedral VNPs, such as CCMV, CPMV, or
Carnation mottle virus
(CarMV),
2
have been successfully self-assembled using the LbL approach (Lin, 2008;
2
CarMV is a plant virus in the Carmovirus genus. The particles have icosahedral
3 symmetry
and a diameter of about 28 nm. CarMV is a single-stranded RNA virus. It naturally occurs in plants
from the family
T =
and is widespread and common in carnation [from Description
of Plant Viruses (DPV): www.dpvweb.net].
Caryophyllaceae
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