Biomedical Engineering Reference
In-Depth Information
empty. virus. particles. can. form. in. vitro,. they. are. less. stable. than. their. RNA. containing.
counterpart.and.do.not.exhibit.the.same.swelling.behavior..Instead,.they.disassemble.at.
higher.pH,.which.highlights.the.importance.of.RNA.for.CCMV.stability.
7.2.2 Diagnostics
Viral.protein.cages.are.excellent.platforms.for.multivalent.display,.where.various.molecules.
can. be. immobilized. on. the. capsid. exterior. for. added. functionality.. CMMV. is. no. excep-
tion;.approximately.11.carbonyl.and.6.lysine.groups.from.each.coat.protein.are.exposed.
on. the. surface. and. can. potentially. be. used. for. ligand. attachment. via. conventional. bio-
conjugation.chemistries..The.possibility.to.introduce.cysteine.residues.in.the.C-terminus.
expands.the.surface.modiication.options.to.include.thiol.chemistries..All.the.aforemen-
tioned.strategies.have.been.used.to.attach.luorescent.dyes.with.up.to.560.molecules.per.
capsid.(Gillitzer.et.al..2002)..Surface-exposed.lysine.groups.have.been.used.to.immobilize.
up.to.360.tetraazacyclododecane.tetraacetic.acid.(DOTA).ligands.(illustrated.in.Figure.7.3)..
DOTA. eficiently. chelates. Gd
3+
. ions. and. transforms. the. virus. into. a. high-performance.
MRI.contrast.agent.with.potential.use.in.diagnostics.(Liepold.et.al..2007).
7.2.3 Material Templating
The. pH. swelling. behavior. and. electrostatic. properties. of. empty. CCMV. particles.
allow. metal-containing. salts. to. selectively. enter. the. capsid. and. be. entrapped. to. form.
O
N
O
O
-
O
O
O
N
N
NH
2
O
-
O
N
N
O
-
O
GdCl
3
NH
O
-
O
O
N
N
Gd
3+
O
-
O
N
N
O
-
O
Figure 7.3
(See companion CD for color igure.)
.Illustration.of.DOTA.conjugated.to.CCMV,.chelating.Gd
3+
.for.MRI.imaging.
