Biomedical Engineering Reference
In-Depth Information
In another study, a silver-plated DNA and AuNP assemblies were used for
the detection of sequence-specific protein-DNA interactions.
107
In this study,
a single AuNP was used for photon bursting in a highly focused laser beam
due to the plasmon resonance scattering and Brownian motion of AuNPs to
develop homogeneous sandwich immunoassays for cancer biomarkers, such as
carcinoembryonic antigen (CEA) and alpha fetal protein (AFP), and aptamer
recognition for thrombin. The detection limits were reported at 130 fM for CEA,
714 fM for AFP, and 2.72 pM for thrombin.
Resonance light scattering in a microarray format was applied for the detec-
tion of proteins and protein functionality kinase activity.
108
The sensor was
based on tagging a specific antibody-protein binding or peptide phosphoryla-
tion events through attachment of AuNPs that was followed by silver deposition
which lead to signal enhancement. Similarly, Sun et al.
109
reported the develop-
ment of a new kinase microarray for detection of kinase inhibition. This assay
also involved tagging peptide phosphorylation and biotinylation events via the
attachment of AuNPs that was followed by silver deposition for signal enhance-
ment. The α-catalytic subunit of cyclic adenosine 5′-monophosphate-dependent
protein kinase (PKA) and its substrate, kemptide, were used for monitoring
phosphorylation and inhibition. This sensor showed highly selective inhibition
of PKA with the four inhibitors: H89, HA1077, mallotoxin, and KN62 with the
inhibition assay demonstrating the ability to detect kinase inhibition as well as
derive IC
50
(half-maximal inhibitory concentration) plots.
A protein immunoassay sensor for human immunoglobulin G (h-IgG)
used AuNP-based Raman label for protein detection with SERS.
110
They used
2- to 5-nm size AuNPs as labels that were attached to goat anti-h-IgG labeled
with fluorescein isothiocyanate (FITC). These modified NPs were used for the
detection of h-IgG using commercially available nitrocellulose strip with silver
enhancement. The FITC was used as a Raman probe and its vibrational finger-
print was used for the detection of h-IgG at 1-100 ng/µl concentration.
NPs had also been used for the development of an IgE receptor (FcεRI)-
targeted, pH-sensitive SERS nanosensor.
111
The nanosensor was used for spa-
tial and temporal pH measurements. The targeting molecules on the NP were
used to monitor internalization progress through the endosomal compartments
in live cells. The results indicated slower progression of receptors through low-
pH endocytic compartments at the lower temperature. The nanosensor was also
used to directly measure changes in the pH of intracellular compartments after
treatment with bafilomycin or amiloride. The sensors indicated an increase in
endosome compartment pH after treatment with bafilomycin, an H(+) ATPase
pump inhibitor while a decreased endosomal luminal pH was measured in
cells treated with amiloride that was an inhibitor of Na(+)/H(+) exchange. The
pH decline in amiloride-treated cells was transient with a recovery period of
about 15-20 min to restore endosomal pH. The studies demonstrated the use of
SERS to monitor local pH environment in living cells with the use of targeted
nanosensors.
