Fabrication of hollow particles composed of silica containing gadolinium compound and magnetic resonance imaging using them

A preparation method for hollow particles composed of silica shell containing gadolinium compound (GdC) is proposed. GdC nanoparticles with an average size of 40.5 ± 6.2 nm were prepared with a homogeneous precipitation method at 80°C using 1.0 × 10−3 M Gd(NO3)3 and 0.5 M urea in the presence of 2.0 × 10−4 M ethylenediaminetetraacetic acid disodium salt dihydrate. Silica-coated GdC (GdC/SiO2) nanoparticles with an average size of 100.9 ± 9.9 nm were fabricated with a sol-gel method at 35°C using 5.0 × 10−3 M tetraethylorthosilicate, 11 M H2O, and 1.5 × 10−3 M NaOH in ethanol in the presence of 1.0 × 10−3 M GdC nanoparticles. The GdC/SiO2 particles were aged at 80°C in water after replacement of solvent of the as-prepared GdC/SiO2 particle colloid solution with water, which provided diffusion of GdC into the silica shell and then formation of a hollow structure. The hollow particle colloid solution revealed good MRI properties. A relaxivity value for longitudinal relaxation time-weighted imaging was as high as 3.38 mM−1 · s−1 that attained 80% of that for a commercial Gd complex contrast agent.