Improving Proton Relaxivity of Dendritic MRI Contrast Agents by Rigid Silsesquioxane Core

We report that the cubic octameric polyhedral oligomeric silsesquioxanes (POSS)-core dendrimers, novel gadolinium (Gd) chelators, enhanced the proton relaxivity to Gd3+. The stability of the Gd complex with POSS(G1.5) was similar to those of DOTA and DTPA. From the MTT assay with the primary hepatocytes, the cytotoxicity of [Gd2POSS(G1.5)](2-) showed lower than that of the [Gd(DOTA)](-) complex. The detection limits were approximately 100-fold improved than those of DOTA and DTPA-Gd complexes in the MR images.