Mn(II)-Based MRI Contrast Agent Candidate for Vascular Imaging.

Toxicity concerns related to Gd(III)-based magnetic resonance imaging (MRI) agents prompted an intensive research toward their replacement by complexes of essential metal ions, like Mn(II). Here, we report a macrocyclic chelate, [Mn(PC2A-BP)], which possesses high thermodynamic stability (log KMnL = 14.86 and pMn=8.35) and kinetic inertness (t1/2pH=7.4 = 286.2 h) as well as as remarkable relaxivity (r1p = 23.5 mM-1 s-1, 0.49 T, 37 °C) in the presence of human serum albumin, allowing a significant MRI signal intensity increase in the vasculature even at low dose (25 μmol/kg) of the complex.