Slide- and Micoarray-Based Biosensors Using Noble Metal Nanoparticles - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 68

The NMNPs can also be applied to biosensing in a dry-reagent
dipstick format. The dry-reagent dipstick test has been widely used
for pregnancy test, which is essentially an immunochromatographic
assay for human chorionic gonadotropin, with all required reagents
deposited in a dry form on a suitable strip. Test strips based on gold
nanoparticle as the visual indicator have already been commercialized
for pregnancy diagnosis. Ioannou and coworkers have extended the
assay to detection of genetically modiied organisms (GMO) 61 and
genotyping. 62 The principle of the visual detection of ampliied
DNA fragments, by using the nanoparticle-based DNA biosensor, is
illustrated in Fig. 4.9 (Left). Typical photographs of two dry-reagent
dipsticks for the hybridization analysis of ampliied lectin DNA is
shown in Fig. 4.9 (Right).
Figure 4.9 (Left) Schematic illustration of the principle of the
nanoparticle-based DNA biosensor for visual detection of
GMO. Biotinylated PCR product is hybridized to a speciic
oligo(dA)-tailed probe and loaded on the sample application
area (S) of the sensor. As the buffer migrates upward (direction
of the arrow), it rehydrates the oligo(dT)-conjugated gold
nanoparticles, which are then coupled with the DNA target
through poly(dA/dT) hybridization. The irst red line is formed
in the test zone (TZ), as the immobilized streptavidin captures
the hybrids. The second red line is developed on the control
zone (CZ), when the excess of conjugated gold nanoparticles
hybridize with immobilized oligo(dA) probe. Au, conjugated
gold nanoparticles; B, biotin; SA, streptavidin. (Right)
Hybridization assay of ampliied lectin DNA by using the dry-
reagent dipsticks. A PCR negative (N) and a positive samples
(S) are shown. TZ, test zone and CZ, control zone. Reprinted
with permission from Ref. 61, Copyright 2006, Elsevier.