Relaxividade de nanopartículas de óxido de ferro com diferentes recobrimentos em equipamentos clínicos de ressonância magnética

Abstract

In the present study, some physical characteristics and nuclear magnetic relaxation properties of iron oxide nanoparticles coated with different coatings and synthesized in our laboratories were investigated. Eight nanoparticle systems were obtained, one of these systems being a linked fluorophore group (Cy5.5). Raman spectroscopy and X-rays diffraction have shown that the iron oxide in question is magnetite. The magnetization measurements revealed superparamagnetic behavior of the nanoparticles due to the absence of hysteresis of the nanoparticles and a saturation magnetization ranging from 3.8-61.6 emu/g. The iron concentration of each synthesis was obtained by UV-Vis spectrophotometry and relaxometry and the results obtained ranged from 0.46-11.2 mg/mL. ZFC/FC measurements showed a distribution of the blocking temperature of the nanoparticles not exceeding 50 K. Aqueous solutions with different concentrations of the nanoparticles and the Lumirem commercial contrast agent were prepared to give the relaxation times T1 and T2 and the relaxivities r1 and r2. In these measurements, the nanoparticles showed contrast effects, disturbing the signal intensity, decreasing the relaxation times T1 and T2. The ratio of relaxivities (r2/r1) ranged from 3.13-64.14, which is within the values of the commercially available iron oxide contrast agents. It is concluded that the nanoparticles evaluated in this work are suitable as a T2-type contrast agent.