Lipid-Based Pharmaceutical Nanocarriers for Imaging Applications - Nanotechnology for Biomedical Imaging and Diagnostics - page 69

3.5.2 some recent trends

recent developments with diagnostic liposomes and lipid-core micelles deal mainly
with utilizing new imaging modalities (such as optical imaging) and with making
more and more advanced theranostic agents.
in addition to already mentioned nanocarriers loaded with Qd, cetuximab-labeled
liposomes have been colabeled with fluorescent indocyanine green, showed good
binding with A431 colon carcinoma cells, demonstrated high quantum yield, and
were suggested as nanosystems combining targetability and imaging properties
[154]. Near-infrared quantitative imaging of lymphatic functions (lymphatic flow)
was performed using the liposomal formulation of indocyanine green, which in free
form is very unstable in solution [155]. pEgylated dspC-liposomes with incorpo-
rated fluorescence-labeled dodecaborate lipid were shown to accumulate well in
tumors except hypoxic regions [156]. These are just few examples of fast developing
near-infrared optical imaging (especially useful for animal experiments) using lipid-
based nanocarrier systems.
developing theranostic nanosystems, liposomes have been prepared coated with
d-alpha-tocopheryl pEg 1000 succinate monoester and containing both docetaxel
and Qd [157]. in cell culture experiments, these liposomes showed good uptake by
mCf-7 cancer cells and are suggested to improve cancer imaging and therapy. Very
interesting theranostic liposomes have been described in [158], where the authors
combined in a single preparation doxorubicin (as a drug postloaded into contrast-
labeled liposomes) and fluorescent tracer (for near-infrared imaging), 64 Cu (for pET
imaging) or 99m Tc (for spECT imaging), and gd in amphiphilic chelate (for mri). A
novel class of dual 1H-mri probes—gd-doped LipoCEsT agents—was described,
where liposomes contain a shift reagent in the aqueous core and gd complex on the
external surface [159]. such probe can serve as T1 contrast, but after the cleavage
and removal of the gd coating, it works as a CEsT contrast. Combined magneto-
photo-acoustic imaging was achieved by using liposomes coloaded with gold
nanorods and iron oxide nanoparticles [160]. similar studies are too numerous to be
listed all, but the examples presented demonstrate well the general direction in which
the approach is developing.

3.6 coNcLudiNg remarKs

perhaps, the key benefit of liposome- or micelle-based diagnostic is the ability to cre-
ate high local concentrations of imaging/contrast agent and thus better “image” (i.e.,
evaluate) functional characteristic of a tissue or other region of interest. As long as an
understanding of the characteristics of the lipid-based nanocarrier and how it interacts
with the biological milieu exists, it should be possible to design diagnostics that make
these functional measurements possible. The data obtained so far leads to a definite
conclusion that contrast-loaded liposomes and micelles may be and will be success-
fully used for visualization of numerous organs, tissues, and disease sites in all imaging
modalities. The advantages of gamma-imaging and mri with liposomes (and, more
recently, with micelles) have been already demonstrated in many experimental and