Metallostar Assemblies Based on Dithiocarbamates for Use as MRI Contrast Agents

Area of Science:

• Inorganic Chemistry
• Materials Science
• Radiology

Background:

• Gadolinium chelates are crucial for Magnetic Resonance Imaging (MRI) contrast agents.
• Enhancing relaxivity (r1) of gadolinium complexes is key to improving MRI sensitivity.
• Developing novel multimetallic complexes offers opportunities for superior contrast agents.

Purpose of the Study:

• To synthesize and characterize novel bi-, tri-, and tetrametallic d-f mixed-metal complexes.
• To investigate the effect of restricted chelate rotation on relaxivity.
• To evaluate the performance of these new complexes as potential high-performance MRI contrast agents.

Main Methods:

• Synthesis of octadentate gadolinium chelates (DO3A, DOTAGA) and their incorporation into d-f mixed-metal complexes using piperazine-based dithiocarbamate linkers.
• Relaxivity (r1) measurements at 10 MHz and 63.87 MHz at 25 °C.
• Comparison of relaxivity values with clinically approved agents like Dotarem.

Main Results:

• Relaxivity (r1) values increased with the number of gadolinium units and overall complex mass.
• A trigadolinium complex with a ruthenium(III) core achieved an r1 value of 9.2 mM-1 s-1 per Gd unit at 10 MHz.
• An 86% increase in relaxivity per gadolinium unit was observed at 63.87 MHz compared to Dotarem for a multimetallic compound.
• Gadolinium complexes based on DOTAGA also showed high performance, with an r1 of 9.5 mM-1 s-1 per Gd unit for a trigadolinium complex.

Conclusions:

• Piperazine-based dithiocarbamate linkers effectively restrict chelate rotation, enhancing relaxivity.
• Multimetallic d-f hybrid complexes demonstrate significant potential as high-performance MRI contrast agents.
• The dithiocarbamate coordination chemistry offers a versatile route to novel MRI contrast agents with tunable properties.