Desenvolvimento de sondas nanoestruturadas de óxido de ferro para imageamento biomédico não invasivo

Abstract

In this work we investigated the synthesis, characterization and contrast properties of core-shell nanoparticles of iron oxide coated with dextran and functionalized with amine groups. Fluorophores groups were incorporated on the nanoparticles surface, allowing their use as contrast agents for magnetic resonance imaging and optical microscopy. The nanoparticles synthesis was performed by the coprecipitation method of iron salts in basic medium, along with the polymer coating. The synthesis parameters were modified to investigate their influence on the size distribution of nanoparticles. Transmission electron microscopy observations and dynamic light scattering showed a magnetic iron oxide core with an average diameter around 10-15 nm and the total average hydrodynamic diameters between 16-50 nm, depending on the synthesis conditions. The FTIR spectra showed characteristics absorption bands pure dextran in the synthesized core-shell nanoparticles. The zeta potential analysis showed positive values close to zero and stability at neutral pH. The magnetization curves of the nanoparticles revealed superparamagnetic behavior, with the characteristic absence of hysteresis and no magnetization at zero field. The UV-vis and flow cytometry analysis revealed the presence of fluorescent groups in the nanoparticles and the feasibility of their use in optical imaging. Studies of relaxation times of the nuclear magnetization have shown the decrease of the magnetic resonance signal with increasing nanoparticles concentration, reducing the relaxation times T1 and T2 in the nanoparticle aqueous solutions. The relaxivities ratios (r2/r1) ranged between 5.06 and 51.0 and were within the value of iron oxide contrast agents commercially available.