402
h. Chon and J. Choo
Recently, surface-enhanced Raman scattering (SERS) spectroscopy has become
a promising alternative that helps to overcome various problems met in case of fluorescence detection. SERS spectroscopy using metal nanoparticles has shown promise in overcoming the low sensitivity inherent to conventional Raman spectroscopy,
as it is possible to obtain an enormous Raman enhancement using hot spots on aggregated metal particle clusters. the SERS detection sensitivity is enhanced up to 10–14
orders of magnitude compared to conventional Raman spectroscopy [8–14]. Consequently, SERS detection provides a sensitivity that is comparable to fluorescence
detection. Furthermore, it is possible to simultaneously detect multiple analytes using SERS because the signals are much narrower than fluorescence bands [15–18].
one of the most popular technologies for the SERS-based immunoassay uses
the typical protocol of a sandwich immunocomplex platform [19, 20], with primary
antibodies immobilized on a substrate with sequentially added antigens and secondary antibody-conjugated Raman probes. After the formation of a sandwich immunocomplex on a substrate, SERS signals are measured and analysed. various kinds
of biomarkers, including immunoglobulin (Igg) antigens [21–23], feline calicivirus
(FCv) [24], prostate-specific antigen (PSA) [25], protein A [26], hepatitis B virus
[27], and mucin protein (muC4) [28], have been investigated using this SERSbased immunoassay technique.
to date, three different types of SERS assay platforms have been developed;
gold-patterned substrates, a platform using magnetic beads, and a device platform
using a microfluidic device. In this chapter, we first introduce various types of SERS
nanoprobes and their bio-conjugation techniques for specific marker targeting. A
novel immunoassay technique for a sensitive detection using SERS spectroscopy
was investigated using three different SERS-based immunoassay platforms, which
were developed for the fast and sensitive detection of biomarker proteins.
14.2 Various Types of SERS Targeting Nanoprobes
for Immunoassay
Silver nanoparticles are widely used as optical enhancing agents in SERS–based
immunoassays because the Raman enhancement factor is 100–1000 times greater
than that of gold nanoparticles. however, silver nanoparticles have disadvantages,
including short-term stability and uncontrollable size distribution. gold nanoparticles are a more attractive choice for SERS-based immunoassays because of their
favourable chemical properties and stability. In addition, aggregation is required for
a large signal enhancement because the electromagnetic enhancement effects are
greatly increased at the hot-spot junctions between particles. this aggregation process leads to poor homogeneity because it is nearly impossible to control the shapes
and sizes of the nanoparticles. Consequently, the potential for structural control of
large local fields of hot-spot junctions has attracted much interest in the fabrication,
assembly, and properties of structures with nanoscale gaps.
metal nanostructures with hollow interiors have been investigated by many research scientists. these are commonly prepared by coating the surfaces of colloidal
h. Chon and J. Choo
Recently, surface-enhanced Raman scattering (SERS) spectroscopy has become
a promising alternative that helps to overcome various problems met in case of fluorescence detection. SERS spectroscopy using metal nanoparticles has shown promise in overcoming the low sensitivity inherent to conventional Raman spectroscopy,
as it is possible to obtain an enormous Raman enhancement using hot spots on aggregated metal particle clusters. the SERS detection sensitivity is enhanced up to 10–14
orders of magnitude compared to conventional Raman spectroscopy [8–14]. Consequently, SERS detection provides a sensitivity that is comparable to fluorescence
detection. Furthermore, it is possible to simultaneously detect multiple analytes using SERS because the signals are much narrower than fluorescence bands [15–18].
one of the most popular technologies for the SERS-based immunoassay uses
the typical protocol of a sandwich immunocomplex platform [19, 20], with primary
antibodies immobilized on a substrate with sequentially added antigens and secondary antibody-conjugated Raman probes. After the formation of a sandwich immunocomplex on a substrate, SERS signals are measured and analysed. various kinds
of biomarkers, including immunoglobulin (Igg) antigens [21–23], feline calicivirus
(FCv) [24], prostate-specific antigen (PSA) [25], protein A [26], hepatitis B virus
[27], and mucin protein (muC4) [28], have been investigated using this SERSbased immunoassay technique.
to date, three different types of SERS assay platforms have been developed;
gold-patterned substrates, a platform using magnetic beads, and a device platform
using a microfluidic device. In this chapter, we first introduce various types of SERS
nanoprobes and their bio-conjugation techniques for specific marker targeting. A
novel immunoassay technique for a sensitive detection using SERS spectroscopy
was investigated using three different SERS-based immunoassay platforms, which
were developed for the fast and sensitive detection of biomarker proteins.
14.2 Various Types of SERS Targeting Nanoprobes
for Immunoassay
Silver nanoparticles are widely used as optical enhancing agents in SERS–based
immunoassays because the Raman enhancement factor is 100–1000 times greater
than that of gold nanoparticles. however, silver nanoparticles have disadvantages,
including short-term stability and uncontrollable size distribution. gold nanoparticles are a more attractive choice for SERS-based immunoassays because of their
favourable chemical properties and stability. In addition, aggregation is required for
a large signal enhancement because the electromagnetic enhancement effects are
greatly increased at the hot-spot junctions between particles. this aggregation process leads to poor homogeneity because it is nearly impossible to control the shapes
and sizes of the nanoparticles. Consequently, the potential for structural control of
large local fields of hot-spot junctions has attracted much interest in the fabrication,
assembly, and properties of structures with nanoscale gaps.
metal nanostructures with hollow interiors have been investigated by many research scientists. these are commonly prepared by coating the surfaces of colloidal