Biomedical Engineering Reference
In-Depth Information
+
(a)
+
+
(b)
Nonessential nucleotides:
Target molecule:
Essential nucleotides:
Complementary oligonucleotides:
Figure 2.2
(See companion CD for color igure.)
. Aptamer. truncation. based. on. intermolecular. hybridization.. (a). The.
nonessential.nucleotides.of.a.selected.aptamer.are.hybridized.with.complementary.oligonucleotides..(b).The.
essential.nucleotides.of.the.aptamer.are.hybridized.
determined. by. comparing. the. predicted. secondary. structures.. The. advantage. of. this.
method.is.that.it.is.economical.and.time.saving..However,.the.system.used.for.software.
prediction. only. contains. aptamers,. whereas. a. real. system. contains. both. aptamers. and.
their. target. molecules.. In. fact,. the. secondary. structures. of. aptamers. often. change. upon.
binding. to. the. targets,. which. has. been. demonstrated. by. various. experimental. methods.
(e.g.,.nuclear.magnetic.resonance.[NMR].[Lee.et.al..2005a],.atomic.force.microscopy.[AFM].
[Jiang.et.al..2003],.x-ray.scattering.[Jaeger.et.al..1998],.luorescence.correlation.spectroscopy.
[FCS]. [Werner. et. al.. 2009],. and. electron. paramagnetic. resonance. spectroscopy. [EPR].
[Kensch.et.al..2000]).
Recently,.a.new.aptamer.truncation.method.was.reported.by.applying.a.series.of.short.
complementary.oligonucleotides.as.molecular.guides.to.ind.the.most.critical.region.of.a.
selected.aptamer.(Zhou.et.al..2011)..The.concept.of.this.new.method.is.based.on.the.bind-
ing. stability. of. a. double-stranded. DNA.. In. brief,. when. complementary. oligonucleotides.
hybridize. with. the. nonessential. nucleotides,. the. hybridized. aptamer. will. have. similar.
binding.afinity.to.the.target.as.the.original.aptamer..On.the.other.hand,.if.complementary.
oligonucleotides. hybridize. with. the. essential. nucleotides,. the. hybridized. aptamer. will.
have.less.binding.afinity.which.will.be.determined.by.the.length.of.the.hybridized.essen-
tial.region.(Figure.2.2)..This.method.greatly.speeds.up.the.process.of.aptamer.truncation.
2.3 Applications of Aptamer-Functionalized Nanomaterials
Cell.recognition.plays.an.essential.role.in.biological.and.biomedical.applications,.including.
cell.separation,.biosensing,.bioimaging,.drug.delivery,.etc..Cell.recognition.relies.on.vari-
ous.receptor-ligand.interactions..However,.most.natural.ligands.can.be.easily.denatured.
