Lipid-Based Pharmaceutical Nanocarriers for Imaging Applications - Nanotechnology for Biomedical Imaging and Diagnostics - page 66

mri of rabbit brain was achieved after intracarotid administration of large multive-
sicular nanocarriers loaded with paramagnetic metals chelated by dTpA [133]. Certain
data are available on the accumulation of liposomal nanocarriers in sites of experimen-
tally induced arthritis in a rat model [132]. phagocytes within the inflammatory lesion
may also play a role in the enhanced accumulation of liposomes.
Nebulized liposomal gadobenate dimeglumine contrast agent was also used for
mri of larynx and trachea [134] and could be utilized for improved mucosal surface
visualization and early diagnosis of diseases originating in these organs. Cationic
gd-dTpA liposomes have been used also for highly efficient labeling of mesen-
chymal stem cells and cell tracking with mri [135]. paramagnetic probes incorpo-
rated into drug-loaded pH-sensitive liposomes have also been used to follow the
process of the pH-mediated drug release [136].

3.5 diagNostic appLicatioNs of miceLLar imagiNg ageNts

While the delivery of therapeutics by micelles is relatively well developed and elab-
orated [18], the application of micellar formulation as vehicles for contrast agents is
still under development. Apart from the practical value for diagnosis itself, this area
has significant importance for delivery of drugs as it allows visualization of the exact
sites of the drug carrier deposition within the body with extraordinary anatomical
resolution [43, 137].

3.5.1 In Vivo gamma and magnetic resonance visualization
with micellar imaging agents

in experiments on lymphatic imaging [138], amphiphilic chelating probes, gd( 111 in)-
dTpA-pE and 111 in-dTpA-sA, have been successfully incorporated into pEg
(5 kda)-pE micelles (20 nm in diameter), and these nanoparticulate agents were used
in experimental percutaneous lymphography using γ-scintigraphy and mri in
rabbits. The localization of 111 in-labeled dTpA-sA/pEg (5 kda)-pE micelles in local
lymphatics after subcutaneous administration of a 20 μCi dose into the dorsum of a
rabbit hind paw has been demonstrated. The popliteal lymph node can be visualized
within seconds after injection. it was shown that the micelles as smaller particles
exhibit higher accumulation in the primary lymph node.
As the aforementioned data demonstrates, the micellar particulates due to their
size and surface properties can be moved with ease from the injection site along the
lymphatics to the systemic circulation with the lymph flow. in rabbits, T1-weighted
transverse mr images of the axillary/subscapular lymph node area could be obtained
by very fast after subcutaneous injection of small doses of gd-dTpA-pE/pEg
(5 kda)-pE micelles. The collecting lymph vessel and axillary lymph node become
visible only 4 min after administration of gd-containing micelles [138]. Taking into
account the ease and speed with which the primary lymph nodes may be visualized,
one can suggest that unlike the other lymphotropic contrast media, polymeric
micelles are lymphangiographic in nature. Their action is based on the visualization