Encapsulating Materials within VNPs - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 123

Brome mosaic virus Cowpea chlorotic mottle virus

example, (BMV),

Red clover necrotic mottle virus

(CCMV), and (RCNMV). Here, the

material is infused into particles in the swollen form, that is, the “open”
conformation. Dialysis against the appropriate buffers allows reversal
of the swelling and the particles will return to the non-swollen “closed”
conformation. The materials that diffused into the open capsids are thus
entrapped (discussed in Section 5.1).

2. Constrained materials synthesis

VNPs have been exploited as constrained reaction vessels. Here,
precursor materials diffuse into the interior cavity of assembled VNPs,
where nucleation and mineralization of the material occurs leading
to the synthesis of inorganic nanocrystals. Materials synthesis within
VNPs has been extensively studied using the icosahedron CCMV and the
rod TMV; these techniques will be discussed in Chapter 6.

3. Encapsulation during self-assembly

In vitro self-assembly mechanisms can be exploited to selectively

entrap materials within a virus-like particle (VLP). Here, the particles
are disassembled into coat protein monomers. The monomers are then
mixed with the material of interest and re-assembled. If successful, the
VLP assembles around the artificial cargo. Encapsulation of polymers,
synthetic nanoparticles, and enzymes has been demonstrated using the
self-assembly strategy and will be discussed in Section 5.2.

.1 InFuSIon oF MAterIAlS Into ASSeMBled VnPs

One of the first major papers published in the field of viral nanotechnology
dealt with the exploration of VNPs as nanocontainers to host artificial cargo
and as constrained reaction vessels for materials synthesis (Douglas &
Young, 1998). (The utilization of CCMV as a constrained reaction vessel will
be discussed in Chapter 6.) The pH- and metal ion-dependent structural
transitions of the CCMV capsid made it an obvious target to study host-
guest encapsulation and the selective encapsulation of anionic organic
polymers. In this case, polyanetholesulfonic acid (PASA) and polydextran
sulfate (PDS) were packed into the CCMV cage (Douglas & Young, 1998).
CCMV particles in the swollen, open conformation (pH > 6.5 and depletion
of metal ions from the buffer) were exposed to the polymers. Under these
conditions, the polymers have free access to the interior through the 60