Biomedical Engineering Reference
In-Depth Information
Target mRNA
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Reference mRNA
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fIgure 13.9
multiplexed nanoflare. In this nanoparticle antisense imaging system, a gold
nanoparticle is used as a carrier and fluorescence quencher. The amount of a target mRNA
sequence is recorded by the ratio of the signal arising from the target mRNA to that from a
reference mRNA sequence. entry into the cell is thought to occur via endocytosis mediated by
bound serum proteins, but how the nanoparticle escapes the endosomes is not known.
a complementary ODN strand bearing a fluorescent molecule. In the absence of
target mRNA, the fluorescence of the fluorophore would be quenched, but upon
binding of the antisense strand to the target mRNA, the strand bearing the fluoro-
phore would be displaced and become fluorescent. Because the fluorescent strand is
released, the fluorescence only reports on the existence of the mRNA and not its
location. By having two antisense strands hybridized to different fluorophore-con-
taining strands, the NP are able to report on the relative ratio of two RNAs, which
would have much greater diagnostic utility than afforded by an individual signal.
These particles appeared to enter cells, presumably by endocytosis via serum pro-
teins bound to the NP [129]. It is not clear how the NP was able to exit the endosomes
as there was no specific functionality present for that purpose. Because the antisense
strand is covalently linked to the gold NP, the target mRNA becomes likewise bound
to the NP and may sterically inhibit other mRNAs from triggering release of more
fluorescent strands. The antisense strands may also become displaced from the gold
in an exchange reaction with glutathione, which could result in a false signal. Another
problem with the gold NP systems is that they are not biodegradable and often accu-
mulate in the liver, which would not make them ideal for human use [141].
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