A Eu^II‐Containing Cryptate as a Redox Sensor in Magnetic Resonance Imaging of Living Tissue

TLDR

Eu(II) ions can enhance MRI contrast similarly to Gd(III), but their tendency to oxidize to Eu(III) has limited in vivo studies to in vitro work. This study aims to characterize a Eu(II)-containing cryptate in solid and solution phases and to demonstrate its first in vivo MRI contrast application. The authors performed solid- and solution-phase characterization of the Eu(II)-cryptate to enable its use in living tissue. The Eu(II)-cryptate coordinates one to two water molecules upon dissolution, and its contrast enhancement remains observable for hours in a mouse.

Abstract

The Eu(II) ion rivals Gd(III) in its ability to enhance contrast in magnetic resonance imaging. However, all reported Eu(II)-based complexes have been studied in vitro largely because the tendency of Eu(II) to oxidize to Eu(III) has been viewed as a major obstacle to in vivo imaging. Herein, we present solid- and solution-phase characterization of a Eu(II)-containing cryptate and the first in vivo use of Eu(II) to provide contrast enhancement. The results indicate that between one and two water molecules are coordinated to the Eu(II) core upon dissolution. We also demonstrate that Eu(II)-based contrast enhancement can be observed for hours in a mouse.