New system of gadolinium based nanoparticles for T1-MR contrast agents which have high T1-relaxivity was developed. It showed non-aggregated, biocompatible properties and no release of free Gd3+ ions. The structure of non-aggregated MSHS/Gd2O3@pAA system was elucidated by TEM and SEM. The specific relaxivities, r1 and r2 values, of the MSHS/Gd2O3@pAA are measured by 4.9T MR scanner, which are higher than those of the commercial Gadovist. Gd3+ ion releasing experiment was conducted by measuring an amount of leached Gd3+, which showed a trace of ions was released. The cytotoxicity of MSHS/Gd2O3@pAA was examined on MDA-MB 435S cells, which showed no appreciable toxicity in the cells.
