Slide- and Micoarray-Based Biosensors Using Noble Metal Nanoparticles - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 64

selective binding events, such as the biotin-streptavidin pair
interaction, through a process in which the biotin molecules were
chemically attached to the Au nanorod's surface prior to detection
measurements. Results showed that the peak wavelength of the LSPR
band shifts linearly to the concentration of streptavidin, and detection
limits of 0.42 nM for solutions prepared in buffer 37 and 19 nM
for solutions prepared in serum 38 were achieved. As illustrated in
Fig. 4.5, the detection of various anti-IgG has been also reported
using Au nanorods. 39,40
Hollow gold nanoshells have also been synthesized by
reacting aqueous HAuCl 4 solutions with solid templates such as
silver nanoparticles. 27 The surface plasmon peaks of these gold
nanoshells are considerably red-shifted as compared with solid gold
nanospheres. Comparing gold nanoshells with a mean diameter
of 50 nm and shell thickness of 4.5 nm, gold solid nanospheres of
50 nm in diameter, and gold solid nanospheres of 30 nm in diameter,
the RISs are 409, 60, and 71 nm/RIU, respectively. When the gold
nanoshells were modiied on poly(methyl methacrylate) and
functionalized with anti-transferrin, a detection limit of 5.9 nM for
transferrin was achieved. 41 Because the LSPR of gold nanoshells can
be controlled in the near-infrared region of the spectrum, where
the optical transmission through tissue and whole blood is optimal,
gold nanoshells with a silica core have also been applied to monitor
biomolecular interactions in diluted whole blood. 42
Besides using self-assembly of NMNPs on substrates to prepare
chemical and biochemical sensors, nanosphere lithography
(NSL) has been employed to fabricate nanostructures with highly
tunable localized surface plasmons. 43 Biotinylated Ag triangular
nanoparticles were irst used to detection of anti-biotin, and reached
a detection limit of 0.7 nM (see Fig. 4.6). 44 Modiication of the particle
surface with mannose monosaccharide then illustrated the real time
detection of the binding of concanavalin A to the particle surface. 45
These nanostructures were also used to detect the biomolecules
possibly involved in Alzheimer disease. In the irst experiment,
amyloid-β-derived diffusible ligand (ADDL) was attached to the
surface of Ag triangles to detect the speciic antibody anti-ADDL. 46
In the second experiment, the anti-ADDL antibodies were irst
immobilized onto the surfaces of nanoparticles, and then the
interaction of ADDL with its antibody via a sandwich immunoassay
was analyzed. 47 The detection of anti-ADDL was both carried out on
synthetic and clinical samples.