*2.2.1. Magnetic (iron oxide nanoparticles)*

Magnetic iron oxide nanoparticles are the most investigated material in biomedical techniques, due to its superior biocompatibility with respect to other magnetic materials, either in form of oxides or pure metals. Several types of iron oxides exist in nature and can be prepared in the laboratory. Nowadays, only maghemite (γ-Fe2O3) and magnetite (Fe3O4) are able to fulfill the necessary requirements for biomedical applications. These requirements include sufficiently high magnetic moments, chemical stability in physiological conditions and low toxicity, not to mention the easy and economical synthetic procedures available for the preparation of these materials *(Neuberger et al., 2005)*.

The degree of atomic order in the iron oxide lattice, or in other words its degree of crystallinity, as well as the dispersity of the nanoparticles in terms of size and shape are critical parameters that affect their performance in diagnostic and therapeutic techniques as a contrast agent in magnetic resonance imaging (MRI) and hyperthermia, respectively. These parameters are strongly correlated to the approach for their synthesis *(Maenosono et al., 2008)*.
