Biomedical Engineering Reference
In-Depth Information
An example of such a NP assembly, called nanoaggregate
embedded beads (NAEB), is outlined in the next section. Since the
sensitivity of SERS rivals or surpasses that of luorescence, labeled
SERS detection can be used in almost all circumstances that a
luorophor is used. The Raman reporter molecule used in the SERS-
labeled detection should, ideally, have a strong Raman cross section,
and a well-characterized and simple SERS spectrum. Although
common dye molecules have been used extensively in designing
NP assemblies for labeled SERS detection owing to their large cross
sections, their spectral complexity and photosensitivity renders
spectral deconvolution problematic. Many thiol-phenyl derivatives
are much more suitable candidates as SERS reporter molecules.
11.2
NAEB: A Novel SERS-Active
Nanoparticle Assemblies
In this section, we describe one particular NP assembly called
nanoaggregate embedded beads (NAEB) and its application in
pathogen detection. NAEB is fabricated by controlled formation
of small Au NP aggregates adsorbed with reporter molecules
and subsequent encapsulation of these SERS active moieties in a
protective silica shell as outlined in Fig. 11.5A and detailed in
References 55 and 56. NAEB fully utilize the advantage of LSPR
coupling of aggregated NPs thus rendering each nano-sized bead
as an ultrahigh sensitivity SERS nanoprobe. In principle, any
organic molecule with well-characterized Raman spectrum can
be incorporated into NAEB. Speciically, in the example presented
below the Raman reporter molecules (R6G) were incorporated into
the nanoaggregate during the formation process to give each NAEB
a unique Raman signature. Bioconjugation and surface passivation
is performed on the glassy silica shell to enable target-speciic
detection.
Noble metal NPs co-functionalized with Raman reporter and
bio-recognition molecules have been used extensively as biosensors.
However, NAEB has the added advantage of stability. Without the
protective silica shell, even passivated Au or Ag NPs immersed in
biological buffers are prone to parasitic signals from adsorption of
the molecules in the biological luids or loss of signals due to the
desorption of the Raman reporter molecule. In the fabrication of
NAEB, controlled aggregation is achieved by carefully balancing the
Search WWH ::
Custom Search