Optimized PAMAM coated magnetic nanoparticles for simultaneous hyperthermic treatment and contrast enhanced MRI diagnosis

We report the synthesis and characterization of multi-functional monodisperse superparamagnetic
Magnetic NanoParticles, MNPs, able to act as contrast agents for magnetic resonance and Magnetic
Fluid Hyperthermia (MFH) mediators. The investigated samples are constituted of a magnetic core of
magnetite and a biocompatible PAMAM coating. We studied two samples with the same magnetic
volume but different shape, i.e. spherical and faceted. Despite the relatively large size (MNPs of 20 nm
diameter) that generally leads to particles' aggregation and instability, the resulting samples were very
stable. For faceted MNPs, the efficiency in contrasting Magnetic Resonance images, i.e. the nuclear
transverse 1H NMR relaxivity r2, reached values of about 250/300 mM-1 s-1 at clinical frequencies f > 5
MHz, i.e. 2.5/3 times higher than the commercial compound Endorem, while the Specific Absorption
Rate at Hac = 10 kA m-1 and frequency f < 300 kHz (i.e. within the physiological limits) reaches
900 W g-1, suggesting this system as a potentially useful mediator for MFH. The experimental data
strongly indicate the new synthesized MNP systems as good candidates for theranostic applications.