Iron oxide nanoparticles are widely used for biological applications thanks to their outstanding balance between magnetic properties, surface-to-volume ratio suitable for efficient functionalization and proven biocompatibility. Their development for MRI or magnetic particle hyperthermia concentrates much of the attention as these nanomaterials are already used within the health system as contrast agents and heating mediators. As such, the constant improvement and development for better and more reliable materials is of key importance. On this basis, this review aims to cover the rational design of iron oxide nanoparticles to be used as MRI contrast agents or heating mediators in magnetic hyperthermia, and reviews the state of the art of their use as nanomedicine tools.

Covalent attachment, through a phosphonate anchor, of hydrophilic pegylated dendrons on iron oxide nanoparticles results in versatile, robust, and highly relaxing MRI contrast agents.

The current challenge in the field of nanomedicine is the design of multifunctional nano-objects effective both for the diagnosis and treatment of diseases. Here, dendronized FeO 1−x @Fe 3−x O 4 nanoparticles with spherical, cubic, and octopode shapes and oxidized Fe 3−x O 4 nanocubes have been synthesized and structurally and magnetically characterized. Strong exchange bias properties are highlighted in core−shell nanoparticles (NPs) due to magnetic interactions between their antiferromagnetic core and ferrimagnetic shell. Both in vitro relaxivity measurements and nuclear magnetic resonance (NMR) distribution profiles have confirmed the very good in vitro magnetic resonance imaging (MRI) properties of core−shell and cubic shape NPs, especially at low concentration. This might be related to the supplementary anisotropy introduced by the exchange bias properties and the cubic shape. The high heating values of core−shell NPs and oxidized nanocubes at low concentration are attributed to dipolar interactions inducing different clustering states, as a function of concentration. In vivo MRI studies have also evidenced a clustering effect at the injection point, depending on the concentration, and confirmed the very good in vivo MRI properties of core−shell NPs and oxidized nanocubes in particular at low concentration. These results show that these core−shell and cubic shape dendronized nano-objects are very suitable to combine MRI and hyperthermia properties at low injected doses.