MRI with Gadolinium-Based Nanoparticles - Nanotechnology for Biomedical Imaging and Diagnostics - page 242

Also, in order to improve sensitivity, macromolecular pARACesT agents were
developed, such as the pH-sensitive Yb 3+ -dOTAM complex grafted on dendrimers [196].
Lanthanide-loaded liposomes are also under investigation for this kind of applications.
named LipoCesT agents, these nanoparticles are the object of an increasing interest
because of their high versatility with potential to map physiological phenomenon at
low concentrations [72, 192].
While the use of CesT is promising, this relatively young technique still requires
technical development. especially, in the case of pARACesT, in vivo experimenta-
tions are limited to a few studies that show that better sensitivity is required before
human uses become applicable.

8.5 conclusIon

From this review of the recent literature, it appears clearly that Gd 3+ -based nanoparti-
cles have a high potential to improve MRI diagnoses. Their high relaxivity can improve
the sensitivity of the technique and reduce the necessary dose per exam. Furthermore,
their high versatility gives access to new targets and organs that are not easily imaged
with the currently approved CAs. However, concerns about the potential toxicity of
these longer-lasting particles in the body have also risen together with their development.
One of the current biggest challenges for the scientists is the design of nanoparticles
that are highly efficient but also safe for human use. And this last criterion will have
to be addressed with certainty before clinical use can be approved. This makes the
challenge all the more difficult for the scientist as compromises between relaxivity,
stability, biodistribution, and safety of use have to be found. The recent development of
biocompatible and biodegradable nanoparticles shows that this goal could be reached
shortly. The last advances in the design of efficient CAs with other paramagnetic
species than Gd 3+ such as Mn 2+ , Mn 3+ , Fe 3+ , or even Cu 2+ show that alternatives could
be available in the future, especially for patients at risk regarding nsF related to the use
of Gd 3+ -based CAs. Also, the recent discovery of the CesT/pARACesT technique
shows that new targets could be attainable at the molecular level. The combination of
all these advances, together with the development of more and more powerful scanners,
shows that the MRI technique is only at its beginning and that the diagnosis possibil-
ities we can expect from it in the future are virtually unlimited.

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