The magnetic properties of iron oxide nanoparticles and the plasominc properties of gold nanorods can be reflected in a diagnostic tool: indeed these nanoparticles can be used as contrast agents for different imaging techniques, specifically Nuclear Magnetic Resonance (MRI) and Photo-acoustic (PA) respectively.


Differently from the best-known complexes of Gd3+ with polyamminocarboxylic acids, that affect the relaxing time T1 of water molecules, inducing the signal and the consequent imagine of an organ or a tissue, the nanoparticles of magnetic and, in particular, superparamagnetic oxides, influence the relaxing time T2. The design of superparamagnetic nanoparticles for MRI consists of a superparamagnetic core covered and protected by a biocompatible system. Some of these are already approved and used as contrast agents (Feridex® and Revosit®, made up by non-stoichiometric magnetite covered by polysaccharides, dextran and carboxyl-dextran). Given the diagnostic use, the increase of the sensibility of these systems becomes crucial, raising their capacity to reduce quickly the T2 of water molecules. It depends on their crystallinity and dimensions of the particles. Generally, an increase of the diameter of magnetic cores takes to a better capacity to reduce quickly the T2 of water molecules, even if too large dimensions can take to lose the superparamagnetic characteristics. For this purpose, it is possible to aggregate in a controlled way more nanoparticles in clusters. This is the case of SPION aggregated in alkyl-polyetilenimine (PEI) micelles that induce the relaxing time T2 about 3 times quicker than single SPION with the same formulation. Alternatively, it is possible to constrain more SPION in particles of polymeric material of micrometer size, as PLGA (Lee and T. Hyeon, 2012; L. Li, et al., 2013).

The study of pharmacokinetic of nanoparticles developed by Colorobbia was performed by CNR-IFC in previous projects (POR CREO FESR Synergy) and in activities of spontaneous collaboration. In these contexts, thanks to the collaboration between UNI-FI and CNR-IFC, the pharmacokinetic of nanoparticles was studied, as well as the delivery by the use of engineered cells, using the magnetic resonance (ref. Ballerini et al, 2017).

Technologies as (micro) PET / SPECT, (micro) CT, (micro) ECO at high frequency, photoacoustic imaging, spectroscopic imaging of iperpolarized agents, were employed in different configurations for the study of nanostructured materials and their “in vivo” effect. The geography and the dynamic distribution of nanoparticles were assessed, as well as their effect on target organs. In particular the techniques of magnetic resonance and photoacoustic imaging were used, respectively for the study of paramagnetic systems based on magnetite, and the plasmonic nanoparticles or conjugated with other chromophores.