Small, Fluorinated Mn²⁺ Chelate as an Efficient ¹H and ¹⁹F MRI Probe

Area of Science:

• Medical Imaging
• Materials Science
• Radiochemistry

Background:

• Perfluorinated nanoparticles are widely used as 19F MRI probes.
• There is a need for alternative, potentially safer MRI contrast agents.

Purpose of the Study:

• To explore fluorine-containing small manganese (Mn2+) chelates as alternatives to perfluorinated nanoparticles for 19F MRI.
• To evaluate the properties and imaging capabilities of a novel Mn2+ chelate, MnL1.

Main Methods:

• Synthesis and characterization of the MnL1 complex.
• Determination of Mn-F distance using 19F relaxation data.
• Estimation of kinetic inertness and dissociation half-life.
• Measurement of 1H and 19F relaxation acceleration.
• In vitro phantom imaging and in vivo 19F MRI in mice.

Main Results:

• MnL1 exhibits high rigidity, controlled Mn-F distance (8.2 Å), and high kinetic inertness (1285 h half-life).
• MnL1 significantly accelerates 19F relaxation (~150-fold) with moderate line broadening.
• MnL1 also functions as a 1H relaxation agent due to an inner sphere water molecule.
• Successful visualization of MnL1 in phantom and in vivo mouse 19F MRI with high signal-to-noise ratios and short acquisition times.

Conclusions:

• Small, monohydrated, fluorinated Mn2+ complexes like MnL1 hold potential as novel MRI probes.
• These complexes offer combined 1H and 19F MRI detection capabilities.
• Further optimization may be needed for targeted imaging or cell therapy monitoring applications.