Gd and Zn Co-Substituted Magnetite Nanoparticles as High T2 MRI Agents

Monodispersed aqueous ferrofluids of superparamagnetic Gd substituted Zn-Fe ferrite (Fe0.7 Zn0.3 Gdy Fe2 − y O4, y=0, 0.01, 0.025, 0.04 and 0.05) nanoparticles were synthesized via a direct, efficient and environmental friendly citric acid assisted hydrothermal method. Synthesized nanoparticles were characterized by X Ray Powder Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) method. Ferrofluids obtained by this way showed good stability at pH=7 and hydrodynamic sizes lower than 100 nm with polydispersity indexes below 0.2 at high concentrations (>25 mg/ml). Longitudinal (r1) and transverse (r2) relaxivities were measured at 1.5 T and 37°C. The results showed that the substitution of Gd in the structure of Zn-Fe ferrite has a strong effect on the transverse (r2) relaxivity, increasing its value up to 400 s− 1. mM− 1.