Encapsulating Materials within VNPs - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 130

BMV and CCMV particles can be obtained in T = 1, pseudo T = 2, and

T = 3 symmetry. Furthermore, the coat proteins can be assembled into

sheets, stacks, and tubular structures (Bancroft

et al ., 1967; Krol et al ., 1999;

Larson ., 1976; Pfeiffer & Hirth,

1974) (see Section 3.5). Tubular structures, for example, can be obtained
through self-assembly of CCMV coat proteins in the presence of artificial
DNA molecules (Mukherjee

et al ., 2005; Lucas et al ., 2001; Pfeiffer et al

., 2006). Double-stranded DNA molecules
were mixed with CCMV coat protein monomers at varying DNA:coat
protein ratios and exposed to self-assembly conditions. Tubular structures
with a diameter of 17 nm but varying length were obtained (Fig. 5.4)
(Mukherjee

et al

., 2006). The DNA:coat protein ratio governs the length of
the tubes. The tubes of lengths ranging from 200 nm to 1

et al

µ

m were obtained.

5.2.1 Encapsulaion of Syntheic Nanoparicles via Templaing

Metallic, magnetic, or semiconductor nanoparticles find many applications in
materials and medicine. To make use of synthetic nanoparticles as biosensors
for imaging or therapeutic approaches, modification of the material is
required to (i) make the material biocompatible and (ii) introduce sites
for functionalization. Both of these goals can be achieved by encapsulating
the material within a VNP. Two basic principles have been used to achieve
in vitro self-assembly of VLPs around an artificial core (also referred to as

templating). Templating can be achieved by decorating a nanoparticle core
with a so-called origin-of-assembly site (OAS) that initiates coat protein
monomer binding and promotes self-assembly (Section 5.2.1.1). In the
second approach, the synthetic nanoparticle core is coated with negatively
charged polymers to mimic the negatively charged natural cargo, the nucleic
acids (Section 5.2.1.2). Using these approaches, VLPs have been successfully
assembled around a range of nanoparticle cores, such as metallic, magnetic,
and semi-conducting nanoparticles.

..1.1 templated VlP assembly via oAS

Templated assembly using an artificial OAS has been studied using the RCNMV
platform. The

self-assembly process of RCNMV is well understood.
The assembly is initiated and stabilized by an internal protein/RNA cage.
Formation of the protein/RNA cage structure begins with specific recognition
of a viral RNA sequence by the coat protein. This sequence is referred to as
OAS. The OAS is a complex of RNA-1 with a RNA-2 stem loop, also known
as the trans-activator (Sit

in vivo

., 1998). With the detailed knowledge about
the OAS, an artificial OAS was created on a gold nanoparticle. Attachment of
a thiol-terminated DNA analog of the RNA-2 stem loop (also referred to as

et al