Molecular imaging based on magnetic resonance imaging (MRI) requires a contrast agent with high relaxivity and specificity. Much effort has been devoted to this goal over the past decades. In this work, we continue this endeavor by synthesizing an MRI contrast agent that can penetrate the cellular membrane and bind with specific proteins. It was characterized with one- and two-dimensional NMR spectroscopy, NMR micro-imaging, and mass spectroscopy. The target specificity has been further confirmed by both molecular dynamics simulation and micro-imaging on a living biological system. It is one of the largest of peptide-based bioactivated MRI contrast agents, and its relaxivity enhancement factor is among the highest of MRI contrast agents hitherto published. We envision interesting applications and extension of this smart MRI contrast agent with bio-specificity and high contrast for molecular imaging.
Keywords: RGD motif; contrast agent; integrin; intracellular molecular imaging; magnetic resonance imaging; relaxivity.