Tissue Engineering And Nanotheranostics

“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics

Plasmonic Nanoparticles Application in Biosensor and Bioimaging 183

developed a NEST sensor to monitor the cleavage of ds­DNA by

nucleases.^164 A fluorphore­labeled ss­DNA was first modified on the

surface of AuNPs. Due to the flexiblity of ss­DNA, it loops back and

adsorbs to the surface of the AuNPs forming an arch­like structure,

and fluorescence of ss­DNA was quenched by AuNPs. Then, target

DNA was added to hybrid with ss­DNA, forming ds­DNA, and the

fluorescence signal was enhanced by a factor of 120 after the cleavage

of this ds­DNA by S1 nuclease. Meanwhile, Mirkin’s et al. developed

a NEST­based sensor for mRNA detection in living cells, also called

nanoflare sensor (Fig. 7(a)). In this system, AuNPs were modified with

oligonucleotides, which could hybridize with short dye­terminated

fluorescent reporter sequence, and the fluorescence was dark due to

AuNP quenching. When target mRNA appears, the recognized oligo­

nucleotides hybridize with the complementary target sequence and

Fig. 7. Several representative AuNP­based activatable assays for DNA detection:
(a) Target mRNA is capable of displacing the short Cy5 labeled reporter strand
from the hybridized sequence on AuNPs, inducing the fluorescence recovery.
Reprinted with permission from Ref. 173. Copyright 2007, American Chemical
Society. (b) AuNPs self­assembled with multicolor stem–loop probes.