Single-Chain Polymer Nanoparticles for Application in Nanomedicine - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 38

As already mentioned, Perez-Baena and co-workers have
developed a new class of Gd-loaded paramagnetic SCNPs as potential
contrast agents for MRI [46]. The novelty of this original approach
relied on the insertion of the DTPA chelate in the form of a cross-
linker instead of grafting it onto the polymeric chain in a conventional
manner (Figure 2.5).

b)

a)

Gd

Gd

Gd

Gd

Gd

Gd

Figure 2.5 Schematic representation of a conventional Gd-grafted
polymer(a) and a polymer intramolecularly cross-linked with Gd chelates
(b). Reproduced from ref. [46] with permission.

This resulted in the formation of conformationally rigid systems
in which the internal rotation of the Gd-DTPA moieties was restricted.
This is very important, for it has been reported that non-rigid
attachment of the Gd III chelate to the macromolecule, or internal
flexibility are often factors that limit the relaxivity of polymers
containing multiple Gd III centres.
The reader should have noticed that many of the nanoparticle
systems described in this chapter are not soluble in organic solvents,
which is not ideal as far as biomedical applications are concerned.
This is due to the fact that historically, synthetic chemists find it
easier to perform their syntheses and developments in organic
media. Obviously one could envisage that all this knowledge will
be extrapolated to aqueous systems in the very near future, as was
the case for the two examples mentioned above, giving rise to a new
class of powerful nanosystems directly applicable in medicine.

References

1. Minchin, R., Sizing up targets with nanoparticles. Nature Nanotechnology,
2008. 3 : p. 12-13.
2. Lewinski, N., Colvin, V., and Drezek, R., Cytotoxicity of nanoparticles.
Small, 2008. 4 (1): p. 26-49.