High proton relaxivity for gadolinium oxide nanoparticles

Objective: Nanosized materials of gadolinium oxide can provide high-contrast enhancement in magnetic resonance imaging (MRI). The objective of the present study was to investigate proton relaxation enhancement by ultrasmall (5 to 10 nm) Gd2O3 nanocrystals. Materials and methods: Gd2O3 nanocrystals were synthesized by a colloidal method and capped with diethylene glycol (DEG). The oxidation state of Gd2O3 was confirmed by X-ray photoelectron spectroscopy. Proton relaxation times were measured with a 1.5-T MRI scanner. The measurements were performed in aqueous solutions and cell culture medium (RPMI). Results: Results showed a considerable relaxivity increase for the Gd2O3-DEG particles compared to Gd-DTPA. Both T-1 and T-2 relaxivities in the presence of Gd2O3-DEG particles were approximately twice the corresponding values for Gd-DTPA in aqueous solution and even larger in RPML Higher signal intensity at low concentrations was predicted for the nanoparticle solutions, using experimental data to simulate a T-1-weighted spin echo sequence. Conclusion: The study indicates the possibility of obtaining at least doubled relaxivity compared to Gd-DTPA using Gd2O3-DEG nanocrystals as contrast agent. The high T, relaxation rate at low concentrations of Gd2O3 nanoparticles is very promising for future studies of contrast agents based on gadolinium-containing nanocrystals.