Biomedical Engineering Reference
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of a breast cancer marker protein, PDGF AA, to a solution of 11-
mercaptoundecanoic acid-protected 2.0 nm photoluminescent Au
nanodots (L AuND ) leads to the preparation of PDGF AA-L AuND as the
donor (see Fig. 10.8). Thiol derivative PDGF binding aptamers and
13 nm spherical Au NPs are used to synthesize the Apt-Q AuNP acceptor.
The photoluminescence of PDGF AA-L AuND at 520 nm decreases
when photoluminescence quenching occurs between Apt-Q AuNP and
PDGF AA-L AuND . The PDGF AA-L AuND /Apt-Q AuNP -based molecular
light switching system is useful for the analyses of PDGFs and
PDGFα-receptor in separate homogeneous solutions with LODs
of 80 pM and 0.25 nM respectively. In the presence of PDGFs, the
interaction between Apt-Q AuNP and PDGF AA-L AuND decreases as a
result of competitive reactions between the PDGFs and Apt-Q AuNP .
Similarly, the interaction between Apt-Q AuNP and PDGF AA-L AuND
decreases as a result of competitive reactions between PDGFα-
receptor and PDGF AA-L AuND . When using the Apt-Q AuNP as a
selector for the enrichment of PDGF AA and the removal of matrixes
possessing intense background luorescence from cell media and
urine samples, this approach provides an LOD for PDGF AA as low
as 10 pM.
Figure 10.9 Sandwich immunoassay with low quantum yield luoro-
phores. Reprinted with permission from Ref. 28.
At present investigators usually strive to use luorophores with
the highest quantum yields to achieve greater sensitivity. However,
these luorophores sometimes may not be available or may not
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