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Updated: Dec 31, 2025
13:21
Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
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Stable and Inert Mn(II)-Based and pH-Responsive Contrast Agents.
Richárd Botár1, Enikő Molnár1, György Trencsényi2
1Department of Physical Chemistry , University of Debrecen , H-4032 Debrecen , Hungary.
Journal of the American Chemical Society
|January 14, 2020
Summary
Researchers developed a novel Manganese (II) complex using the PC2A-EA ligand. This pH-sensitive contrast agent shows potential for MRI applications in biologically relevant pH ranges.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Biomedical Imaging
Background:
- Developing smart/intelligent contrast agents for Magnetic Resonance Imaging (MRI) based on Manganese (II) ions is challenging due to the labile nature of typical complexes.
- Existing polyaminocarboxylate-type ligands often form unstable complexes with Mn(II), limiting their utility.
Purpose of the Study:
- To report the first example of a Mn(II) complex activated by environmental pH changes.
- To investigate the stability and kinetic inertness of a novel Mn(II) complex with a specific ligand.
- To evaluate the pH-dependent relaxivity of the complex for potential MRI applications.
Main Methods:
- Synthesis and characterization of a Mn(II) complex with the PC2A-EA ligand.
- Determination of thermodynamic stability (log K_MnL) and kinetic inertness.
- Measurement of water exchange rates.
- Assessment of pH-dependent coordination and relaxivity in the biologically relevant pH range (6-8).
Main Results:
- The PC2A-EA ligand forms a thermodynamically stable (log K_MnL = 19.01, pMn = 9.27) and kinetically inert Mn(II) complex.
- The complex exhibits a relatively slow water exchange rate ((4.0 ± 0.2) × 10^7 s^-1).
- pH-dependent coordination of the ethylamine moiety (log K_MnL^H = 6.88) in the pH range of 6-8 leads to pH-sensitive relaxivity.
Conclusions:
- A novel, stable, and kinetically inert Mn(II) complex with pH-activatable properties has been synthesized.
- This complex demonstrates pH-sensitive relaxivity within the biologically relevant pH range, indicating its potential as a smart MRI contrast agent.
- The findings open new avenues for developing targeted and responsive MRI contrast agents.
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