Biology Reference
In-Depth Information
Figure 8.15.
Scheme of the DNA hybridization detection procedure using
the Au nanoparticle-coated latex labels shown in Fig. 8.1 [131], taken with
permission from S. Pinijsuwan, P. Rijiravanich, M. Somasundrum, and W.
Surareungchai,
Anal. Chem
.
80
, 6779-84 (2008). c
American Chemical
Society. See also ColorInsert.
form of detection was used by us to quantify latex-based labels,
following target immobilization, as shown in Fig. 8.15. While this
system is convenient if the experimental objective is to develop the
construction of the labels, it is not an ideal method for real samples.
As shown in Fig. 8.16 target sequences of a one base mismatch can
giveasignificantresponse.Sincewewouldexpectsomemismatched
sequences in the sample to be immobilized also, this would provide
interference. A technique to minimize this form of interference is to
usetwoprobesforonetarget,asshowninFig.8.17.Acaptureprobe
is immobilized on the electrode, and then hybridized to one section
of the target. A signal probe, carrying the label, is then bound to a
remaining section.
Using the single-probe method, a 30-base sequence common to
five strains of
E. coli
could be detected using the latex-based labels,
with detection limits of
∼
25 fM (silver nanoparticles on hollow
capsules) [105] and
∼
0.5 fM (gold nanoparticles on latex) [131], as
shown in Fig. 8.18. The lower detection limit for the second method
