Nanobiosensors - Biosensors and Biosensor Kinetics - page 113

was used to monitor the change in the refractive index as the antibodies bound in a label-free
fashion to the antigens immobilized on the gold nanoparticle sensor surface. They noted that
the maximum sensitivity for detecting antibody concentration is 100 nM. A kinetic analysis
was obtained for the antigen-antibody binding.
The authors report that the gold surface plasmon resonance biosensor is popular. McFarland
et al. (2003) and Stuart et al. (2004) have suggested that nanoparticle-based biosensors may
serve as a useful alternative to detect a wide variety of analytes. Olkhov and Shaw (2008)
point out that when the photon frequency is in resonance with a localized surface plasmon
resonance mode in the conduction band of nanoparticles, these noble metal nanoparticles
exhibit a strong optical extinction in the visible region of the electromagnetic spectrum. Both
scatter and absorption contribute to this optical extinction. Noguez (2007) has indicated that
these nanoparticles may be tuned and thereby optimized for a given application by changing
the fabrication methods for nanoparticles. Note that Noguez (2007) reports that the optical
properties of the nanoparticles may be changed by changing their composition, shape, and
size. Researchers ( Heaton et al., 2001; Haes et al., 2004 ) have indicated that biological bind-
ing events may be monitored by biosensor platforms that use either nanoparticle arrays or
single particles.
Olkhov and Shaw (2008) affirm that high-throughput screening is an area where nanoparticle
arrays may be used effectively. They further confirm that label-free surface plasmon detec-
tion techniques provide the flexibility of not only noting the presence or absence of a partic-
ular biomolecule, but also help determine its concentration. Furthermore, the advantage of an
array is that it helps determine the concentrations of different molecules simultaneously. The
authors indicate that a pattern of molecular expression may thus be generated (for example,
biomarkers). This, they point out, could facilitate personalized medicine for patients. Haes
and van Duyne (2004) indicate that there is a large body of information for single-target mol-
ecule analysis. For multiple analyte detection, Olkhov and Shaw (2008) emphasize that there
is much less information available. Lee et al. (2006) and Phillips et al. (2006) have used the
(SPR) surface plasmon resonance imaging technique to determine protein concentrations in
the 1 nM range. Olkhov and Shaw (2008) have fabricated multiple-target sensor arrays using
gold nanoparticles. They were able to detect antibodies in whole anti-sera by using a light-
scattering sensor array reader. They point out that pure light scattering techniques have not
been used previously in microarray imaging applications.
Olkhov and Shaw (2008) fabricated arrays of gold nanoparticles on glass slides
functionalized with target molecules. They report that the array was imaged in a near-field
configuration and the scattered light collected by a camera. A real-time kinetic analysis
was possible by noting the changes in the scattered radiation intensity, compared with a con-
trol spot intensity. This was done as the target analytes flow over the entire array surface. The
authors synthesized the biophotinic surface on the glass surface of a microscopic slide using