A Gd(III)-labelled self-assembling peptide as a potential pH-responsive MRI contrast agent.

A marine-derived peptide labelled with a Gd(III)-chelate was found to self-assemble depending on the solution pH, accompanied by changes in T 1 -relaxivity ( r 1 ) values when in the dispersed or self-assembled form. Such pH-responsive behavior can be advantageous in the development of macromolecular magnetic resonance imaging (MRI) contrast agents which monitor the tissue physiology.