Chemistry Reference
In-Depth Information
these contrast agents to target
integrins opens the
door to the detection of neo-angiogenosis, which is associated with
the development of tumor, whereas the conjugation of Annexin
A5 to these nanoprobes makes them well suited for the detection
of apoptosis by FI and MRI. The strategy of the research group of
Mulder, which is based on the synthesis of lipid-based nanoparticles,
is very attractive because it leads to a large variety of contrast agents
for multimodal imaging [57]. By a convenient choice of the building
blocks (the lipids, the nanoparticles, the biotargeting groups, etc.),
the behavior of these platforms can be accurately tuned for a
definite application. Recently, they demonstrated that endogenous
nanoparticles (high density lipoproteins, HDL) can be also modified
for multimodal imaging by incorporating paramagnetic and/or
fluorescent lipids but also by including within each HDL nanoparticle
hydrophobic inorganic core such as iron oxide, QD, or gold [59].
Since it is known to migrate to atherosclerotic plaques and remove
cholesterol from macrophages, HDL was exploited by Frias
α
β
and
α
β
v
5
v
3
to
develop a probe for molecular imaging of macrophages [60, 61]. The
inclusion of inorganic core affords additional features for imaging
purposes. For instance, the presence of a hydrophobic gold core in
a paramagnetic and fluorescent HDL allows monitoring gold-HDL
by MRI, FI and X-ray imaging since the high atomic number of gold
element confers to the gold nanoparticles the ability to absorb X-ray
photons.
et al.
4.2.5
Paramagnetic Gold Nanoparticles
One of the most promising applications of nanosizes gold objects
lies in their ability to combine imaging and therapy [62]. Two main
strategies were developed for designing gold nanoparticles that can
be used for imaging and destroying tumors. The first one results from
the properties of gold element, whereas the second one rests on the
tunable optical properties of gold particles. Gold particles are indeed
characterized by strong light diffusion and absorption cross sections,
which are sensitive to the size, shape, and dielectric environment
[63]. By tuning these parameters, gold-based nanomaterials (gold-
coated silica particles and gold nanorods) can be synthesized and
exploited for NIR imaging and therapy as demonstrated by Halas
et al.
[64, 65]. Whatever the size, shape, and
environment of the gold nanomaterials, they strongly absorb X-ray
and El-Sayed
et al.
