(59ai) Synthesis, MR Relaxivities, and in Vitro Cytotoxicity of Ligands Coated Gadolinium Oxide Nanomaterials

Magnetic resonance imaging (MRI) is widely used in modern clinical medicine as a diagnostic tool, and provides noninvasive and three-dimensional visualization of biological phenomena in living organisms with high spatial and temporal resolution. Therefore, considerable attention has been paid to magnetic nanoparticles as MRI contrast agents.

We report a facile method to synthesize high quality and bio-functionalized Gd₂O₃ nanoparticles (BFNPs) for use as contrast agents in MRI. The bonding status of BFNPs were confirmed by FT-IR and TGA analysis. The surface coating amount was estimated to be from 40% to 60% in weight percent from a TGA analysis. High voltage electron microscope (HVEM) shows that the BFNPs were spherical in shape with an average diameter 3 mM. In addition, the bio-compatibility of the nanoparticles were measured by cytotoxicity tests by using human prostate cancer (DU145) and normal mouse hepatocyte (NCTC1469) cell lines which indicated that BFNPs are not toxic up to 250 mM. BFNPs are paramagnetic but have an appreciable magnetic moment at room temperature. This is because Gd(III) has seven unpaired 4f-electrons (S = 7/2). Therefore, appreciable r₁ and r₂ values are expected from sample solutions, which were in fact observed in this study. The r₁ and r₂ values of BFNPs were estimated to be 13.77 to 64.14 s ^-1 mM ^-1 respectively. The high relaxivities provide an opportunity to conduct perfusion MRI experiments with significantly lower concentrations than those needed for current commercial agents. A pronounced positive and negative contrast enhancement was clearly observed in 3 tesla T₁ MR images of a rat with a liver tumor after injection of an aqueous sample solution into a rat tail vein