Bioconjugation of Noble Metal Nanoparticles and Their Applications to Biolabeling and Bioimaging - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 12

wide range of potential applications including surface plasmon
resonance (SPR), 1 surface-enhanced Raman scattering (SERS), 2
biosensing, 3 and use in optoelectronic devices. 4 Noble metal
nanoparticles exhibit a strong optical extinction wavelength due to
localized surface plasmon resonance (LSPR) of their free electrons
upon excitation by an electromagnetic ield. Therefore, these
nanoparticles are usually used as label markers and optical probes
for molecular imaging.
Through appropriate surface modiication, most noble
nanoparticles exhibit high transportation property and prevent
rapid blood clearance rendering tumor-speciic targeting ability. 5,6
Noble metal nanoparticles undergo surface modiication to exhibit
better stability, good biocompatibility, lower cytotoxicity, better
water solubility, and speciic targeting. Cytotoxicity and
biocompatibility are two important factors when using biolabeling
and bioimaging probes of noble metal nanoparticles in live
cells, organs, and bodies. They affect the retention time of the
nanoparticles in live cells, organs, and bodies, and the suficient
tracking time for the detection of bioimages. For example, PEG-
modiied Au nanoparticles can increase the circulation time in blood
compared to Au nanoparticles without any surface modiication. 7
PEG provides the biocompatible property to reduce the uptake
of live cells during blood circulation. The importance of speciic
targeting of nanoparticles is that biomolecule-conjugated noble
metal nanoparticles can target the diseased region, e.g., tumors,
and provide signals that are detected by optical instruments when
applied to detect cancer cells. The accurate labels and images
help us clearly diagnose pathological changes. To only observe a
speciic substrate in a complex system, biomolecule-conjugated
nanoparticles with speciic targeting ability can be used to target
the goal substrate, and the nanoparticles can then be tracked using
an optical system. All applications emphasize the importance of
surface functionality of the nanomaterials, which if used to their
advantage can successfully exploit the properties of the nanoparticles.
As a result, the design of attaching molecules to nanoparticles is
an important area of research. To enable promising biomedical
applications of nanoparticles, the chemistry involved should be
environmentally benign, speciic, compatible in aqueous solution,
lead to minimum side products, and be highly reproducible.