Dextran-Coated Ultrasmall Gd2O3 Nanoparticles as Potential T1 MRI Contrast Agent

Ultrasmall gadolinium oxide (Gd2O3) nanoparticles coated with dextran (M-r= 1500 amu) were prepared through one-pot synthesis and their potential to act as a T-1 MRI contrast agent was investigated. The dextran-coated ultrasmall Gd2O3 nanoparticles were highly water-dispersible, with an average particle diameter of 1.5 nm and an average hydrodynamic diameter of 12.4 nm, and non-toxic, as determined in a cellular cytotoxicity test. The longitudinal (r(1)) and transverse (r(2)) water proton relaxivities were estimated to be 12.2 and 29.3 s(-1) mM(-1) (r(2)/r(1)=2.4), respectively, larger than those of commercial Gd-chelates. This r(1) value is also greater than those for previously reported dextran-coated large Gd2O3 nanoparticles with particle diameter bigger than 20 nm. Positive contrast magnetic resonance (MR) images were obtained after intravenous injection of a sample solution into a mouse tail, demonstrating the potential of dextran-coated ultrasmall Gd2O3 nanoparticles as a T-1 MRI contrast agent.