Biomedical Engineering Reference
In-Depth Information
DNA hybridization assays based on SEF are useful for the
detection of DNA. When luorescein-labeled complementary
oligonucleotide is captured with thiolated-oligonucleotides
that are bound to Ag NPs on a glass substrate, the luorescence
intensity increases 12-fold.
99
This effect is thought to result from
the decreased luorescence lifetime and SEF near metallic Ag
NPs. The effects of SEF on Ag NP-coated glass surfaces have been
measured for two dyes commonly used in DNA microarrays, Cy3
and Cy5.
12
Biotinylated, singly labeled 23 bp DNAs bind to avidin-
coated silver surfaces, resulting in a luorescence enhancement that
is dependent on the DNA spotting concentration. Below ~12.5 μM,
SEF luorescence increases linearly, and at larger concentrations,
SEF luorescence remains at a constant maximum of 28-fold for Cy5
and 4-fold for Cy3 when compared to those on avidin-coated glass
substrates. A detection system consisting of DNA-modiied Ag NPs
and a luorophore-labeled complementary DNA is useful for the
detection of DNA (see Fig. 10.11).
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Figure 10.11
Preparation, displacement by thiolate oligonucleotides,
and hybridization with luorescein-labeled complementary
oligonucleotides of tiopronin-monolayer protected Ag NPs.
Reprinted with permission from Ref. 100.
Single-stranded oligonucleotides displace
N
-(2-
mercaptopropionyl)- glycine (tiopronin) monolayer-protected
Ag NPs through ligand exchanges. The oligonucleotide-displaced
particles can then be hybridized with complementary luorescein-
labeled oligonucleotides. Both the oligonucleotide-displaced and
hybridized particles form aggregates via electrostatic interactions
with salt (10 mM KCl) in buffer solution. Because the aggregates
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