Biomedical Engineering Reference
In-Depth Information
Monovalent
nanomaterial
Aptamer
Fluorophore
O
O
O
NH
2
DCC
N
O
N
COOH
NHS
H
O
Bivalent
nanomaterial
PAMAM:
COOH
Hilyte488 or TD05:
NH
2
Figure 2.3
(See companion CD for color igure.)
.Synthesis.of.the.monovalent.and.bivalent.nanomaterials..The.chemical.
conjugation.is.based.on.the.amide.bond.formation.
functionality.of.this.aptamer-dendrimer.nanomaterial.was.evaluated.by.low.cytometry..
The.results.showed.that.this.hybrid.nanomaterial.could.bind.cells.with.high.afinity.and.
speciicity.
Another.important.feature.of.natural.antibodies.is.multivalency,.which.determines.their.
high.binding.avidity..In.order.to.mimic.this.characteristic,.a.bivalent.antibody-like.nano-
material. was. developed. using. an. aptamer-functionalized. dendrimer. (Zhou. et. al.. 2010)..
The. key. components. of. this. nanomaterial. were. two. DNA. aptamers,. a. double-stranded.
DNA.stem,.and.a.dendrimer..The.aptamers.were.used.to.mimic.the.antigen-binding.sites.
of. natural. antibodies. for. speciic. cell. recognition.. The. double-stranded. DNA. stem. was.
used.to.maintain.the.“Y”.shape.structure..The.dendrimer.was.used.to.provide.a.deined.
conjugation. site. for. carrying. molecules. of. interest. (Figure. 2.3).. The. results. showed. that.
this. bivalent. nanomaterial. exhibited. a. much. higher. binding. afinity. than. the. monova-
lent.control..In.addition,.this.bivalent.nanomaterial.exhibited.a.reversible.cell.recognition.
function..An.environmental.temperature.change.from.0°C.to.37°C.could.trigger.a.rapid.
dissociation.of.the.bivalent.nanomaterial.from.the.bound.target.cells.(Zhou.et.al..2010)..In.
contrast,.natural.antibodies.bind.strongly.to.target.cells,.and.this.strong.binding.is.very.
dificult.to.dissociate.in.an.active.manner.
2.3.2 Aptamer-Functionalized Nanoparticles
Aptamers. can. also. be. used. to. functionalize. nanoparticles. for. speciic. cell. recognition..
The. nanoparticles. are. employed. as. a. drug. carrier. and/or. signal. provider.. Drug-carried.
