Biocompatible superparamagnetic iron oxide nanoparticles used for contrast agents: a structural and magnetic study

The magnetic properties of different biocompatible magnetic iron oxide nanoparticles (MION) are presented. Dextran-coated, magnetite (Fe3O4) MIONs were studied as supplied and after lyophilization, to disentangle the effects of particle interactions. All samples showed superparamagnetic behavior at room temperature, with blocking transitions at T-B similar to 40-56 K (at 100 Oe), depending on the particle interactions. The dynamics of the thermally activated blocking process reveals that the effect of dipolar interactions is to increase the energy barriers of the individual particles. (c) 2004 Elsevier B.V. All rights reserved.