The synthesis and relaxivity of a new gadolinium(III) complex of a Cyclen macrocycle having 2-bromoisovaleric acid pendant arm (DO3VA) and its Dinuclear complex is reported. The longitudinal relaxivity (r1p) of [Gd2{pr(DO3VA)2}(H2O)4] is 11.32 mM-1 s-1 which correspond to a “per Gd” relaxivity of 5.66 mM-1 s-1. The “per Gd” r1p values are higher than that of the clinically approved CAs. The transverse relaxivity of the complex is 12.10 mM-1 s-1 which correspond to a “per Gd” relaxivity of 6.50. The “per Gd” r2p value of the complex is higher than that of the parent complex [Gd(DO3VA)(H2O)2]. The r2p/r1p value of 1.07 for the complex indicates that the complex is T1-weighted CA. The complex exhibits pH-dependent r1p and r2p values at pH 2.6-10.6 indicating their potential use as pH-responsive contrast agent for MRI. The complex exhibit higher r1p values of 30.51 mM-1 s-1 in the presence of HSA indicating the formation of macromolecular adduct with HSA.  

Keywords:  MRA Contrast agents, Blood Pool Agents, MRI, pH-responsive, DO3VA, HSA-Binding.