“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics
Plasmonic Nanoparticles Application in Biosensor and Bioimaging 173
different aptamers in vitro and in vivo. It is noted that color change in
images and peak shift in spectra can be displayed with a single dot by
DFM when catalytic reaction happens, indicating that each individual
nanoparticle in this system acts as an individual plasmonic probe.
Besides, AuNPs were also used as contrast and recognition rea
gents. The catalytic enlargement of AuNPs conjugate associated with
biorecognition complexes is used to yield conductive patterns that
follow biosensing process.119–121 Inspired by catalytic deposition of
production on AuNPs by catalysis, AuNPs have been applied for the
optical and electrochemical detection of biocatalytic processes. Long’s
group^122 utilized AuNPs (50 nm in diameter) to monitor the gold
catalyzed reduction of Cu 2 + ions on AuNPs forming Au@Cu core–
shell nanoparticles by NADH or by NAD+ cofactordependent
enzyme/substrate system. The plasmon spectra of Au@Cu nanoparti
cles redshifted followed the increase in the concentration of NADH.
Therefore, it could be applied to map the distribution of NADH in
cells, following in vitro intracellular metabolic pathways and to screen
drugs affecting cell metabolism.^122 Meanwhile, Fan et al. applied
AuNPs with 50 nm as building blocks for surface attachment of dou
ble stranded (ds) DNA and HRP.^99 As HRP initiates the polymeriza
tion of aniline on dsDNA templates with the addition of H 2 O 2 ,^123
leading to the growth of AuNPs, which changes its true color and
shifts plasmon band, which lay the foundation for plasmonic detec
tion of H 2 O 2. Another work based on the DAinduced seeded growth
of AuNPs was able to monitor the release of DA from living PC12
cells and highlight the concomitant relation of ATPstimulated release
of DA is with the Ca 2 + influx, and the influx of Ca 2 + is through ATP
activated channels.^124 In construct, the depression of growth was
applied to detect RDX residues in LFP. In the absence of RDX resi
dues, NADH mediated the reduction of Cu 2 + and deposition of Cu 0
on AuNP seeds (50 nm), leading to the coating of AuNP with a shell
of Cu, which results in a redshift in the LSPR scattering spectrum,
while, in the presence of RDX, NADH competes between Cu 2 + and
RDX. As a result, the catalytic growth of AuNPs is inhibited, leading
to a weakened nanoplasmonic response.^125
