The effect of metal ions on endogenous melanin nanoparticles used as magnetic resonance imaging contrast agents.

Melanin nanoparticles are of great importance in biomedicine. They have excellent affinity for metallic cations, especially paramagnetic ions, which has sparked interest in their application in the development of magnetic resonance imaging (MRI) contrast agents. In this work, we prepared ultrasmall water-soluble melanin nanoparticles, and investigated the binding properties of melanin toward different metal cations (Gd, Mn, Fe and Cu), and compared their physicochemical properties and the MRI contrast enhancement ability in various metal chelated forms (MNP-PEG-M) in vitro and in vivo.

A multimeric MRI contrast agent based on a closo-borane scaffold bearing modified AAZTA chelates on the periphery.

A multimeric MRI contrast agent based on the closo-borane motif is reported. Twelve copies of a modified AAZTA chelate with an alkyne end group are appended on an azide-functionalized closo-borane motif using Cu(i) catalyzed click chemistry. The presence of two water molecules on the Gd-bound AAZTA chelate results in high relaxivity for the closomer in vitro/in vivo.