Relaxometry Studies of a Highly Stable Nanoscale Metal–Organic Framework Made of Cu(II), Gd(III), and the Macrocyclic DOTP

The macrocyclic ligand DOTP is used to assemble a porous, heterometallic metal–organic framework (MOF). This MOF is miniaturizable down to the nanoscale to form stable colloids, is stable in physiological saline solution and cell culture media, and is not cytotoxic. It shows interesting relaxometric properties with r1 at high field (500 MHz) of 5 mM–1·s–1 and a maximum r1 = 15 mM–1·s–1 at 40 MHz, which remains constant over a wide pH range and increases with temperature.