Effect of Functional Group and Surface Charge of PEG and Dextran-Coated USPIO as a Contrast Agent in MRI on Relaxivity Constant

The challenges in molecular imaging are focused on the development of novel contrast agents with much lower relaxation times. Ultrasmall superparamagnetic iron oxide nanoparticles known as USPIO have been used for a variety of applications such as imaging of cancer, apoptosis, and hyperthermia providing higher signal changes based on weighted susceptibility effects. Although many studies had been performed on USPIO there is still a lack of data on the effects of the physicochemical properties of these nanoparticles (NP) such as hydrodynamic size, surface charge and type of functional groups, which may alter the relaxivity of these NPs. The aim of this study was to evaluate the effect of different functional groups and surface charges of PEGylated and dextran-coated NPs on their magnetic properties. All relaxometry studies were performed using a 3-T magnetic resonance imaging. Our results showed that the impact of charge on magnetic properties is much higher than that of coating thickness. In this respect, particles with positive surface charges showed higher r (2)/r (1) ratios.