Preparation of silica-coated gadolinium compound particle colloid solution and its application in imaging

Abstract

A preparation method for gadolinium compound (GdC) nanoparticles coated with silica (GdC/SiO2) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at 80oC using 1.0x10-3 M Gd(NO3)3, 0.5 M urea and 0-3.0x10-4 M ethylenediaminetetraaceticacid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as 40.5+-6.2 nm, which were colloidally stable, were prepared at an EDTA concentration of 2.0x10-4 M. Silica-coating of the GdC nanoparticles was performed by a Stober method at 35oC using 1.0-10.0x10-3 M tetraethylorthosilicate (TEOS), 11 M H2O and 1.5x10-3 M NaOH in ethanol in the presence of 1.0x10-3 M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of GdC/SiO2 particles with an average size of 106.1+-11.2 nm at a TEOS concentration of 5.0x10-3 M. The gadolinium (Gd) concentration of 1.0x10-3M in the as-prepared GdC/SiO2 particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of GdC/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated GdC/SiO2 colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.