Gd-Aminoethyl-DO3A Complexes: A Novel Class of pH-Sensitive MRI Contrast Agents

Molecular imaging relies on the availability of imaging probes designed to modify their efficiency in the presence of a specific parameter, among which pH is one of the most investigated. Introduction of an aminoethyl moiety into the well-known DO3A platform imparts the desired pH sensitivity to the corresponding Gd3+ complex. The amine group is accessible and easy to functionalize; in particular, the possibility of tuning its pKAH through N-substitution makes it a good pH-responsive functionality to access a novel class of tailored pH-sensitive MRI contrast agents. This was demonstrated by a relaxometric study on a functionalized Gd-DO3A complex bearing a simple primary amine group and comparison with the results of the corresponding N,N-dimethyl analogue.