Chemistry Reference
In-Depth Information
3+
3+
3+
species (Tm
/Er
/Yb
). Moreover, the replacement of Gd-doped
NaYF
leads to luminescent nanoparticles with higher
longitudinal relaxivity
by NaGdF
4
4
r
(
r
= 5.60 mM
−1
s
−1
vs
r
= 0.14 mM
−1
s
−1
).
1
1
1
3+
This improvement is attributed to a higher Gd
concentration on
3+
3+
3+
the surface of the Tm
/Er
/Yb
co-doped NaGdF
nanoparticles
4
as compared to Gd-doped NaYF
nanocrystals. The authors
demonstrated that these nanoparticles meet the criteria for
4
in vivo
imaging because they are characterized by good water-solubility
and low cytotoxicity, besides their attractive optical and magnetic
properties. After intravenous injection, the hydrophilic Tm
3+
3+
/Er
/
3+
Yb
nanoparticles can be followed up both by
fluorescence imaging and by MRI. The
co-doped NaGdF
4
imaging
experiments revealed that these nanoparticles accumulated only
in liver and spleen. Nonspecific accumulation in these organs is
generally ascribed to uptake by resident phagocytes in liver (Kupfer
cells) and spleen (macrophages and B cells). Although this feature
can be exploited for imaging liver and spleen, such nonspecific
accumulation is generally undesirable because it induces a too quick
removal of a large part of contrast agents from the bloodstream. This
can be detrimental for the monitoring of passive or active targeting.
in vivo
and
ex vivo
4.3.3.2 Carbonate particles containing gadolinium (III)
By refluxing aqueous solution containing urea and gadolinium
chloride,
O)
particles can be obtained [99]. The shape (spherical, rhombus-
or rice-shaped nanoparticles) and the size can be tuned by
varying the urea to gadolinium chloride molar ratio. Relaxation
rate measurements revealed that the relaxivities depend on the
size and shape of the particles. In case of 500 nm sized spherical
Gd
amorphous
gadolinium
carbonate
(Gd
O(CO
)
·H
2
3
2
2
= 12.7,
3T). After injection, the behavior of these large particles can be
monitored by MRI. As expected for large particles, accumulation in
liver was observed.
These particles can be functionalized by an aminated polysiloxane
shell due to the hydrolysis-condensation of the aforementioned
mixture of TEOS and APTES (Scheme 4.3). This polysiloxane
shell permits a further functionalization (Scheme 4.5). Due to the
presence of amino groups onto the nanoparticles, gold nanoparticles
can be immobilized since nitrogen atoms have a great affinity to
gold atoms. These gold nanoparticles act as seeds for the growth
O(CO
)
·H
O particles,
r
is equal to 16.5 mM
−1
s
−1
(
r
/
r
2
3
2
2
1
2
1
