Enzyme-Activated Gd3+ Magnetic Resonance Imaging Contrast Agents with a Prominent Receptor-Induced Magnetization Enhancement

Clinically relevant relaxivity enhancement of a magnetic resonance imaging (MRI) contrast agent has been achieved by using prodrug Gd³⁺ complexes (see picture, DTPA=diethylenetriaminepentaaceto). Enzymatic cleavage of lysine residues from the prodrug exposes a group that has a high affinity to human serum albumin and promotes enhanced relaxivity, thus enabling the detection of targets at submicromolar concentrations.