PEGylation of Terminal Ligands as a Route to Decrease the Toxicity of Radiocontrast Re₆-Clusters

Area of Science:

• Inorganic Chemistry
• Materials Science
• Radiology

Background:

• Conventional X-ray contrast media exhibit side effects, necessitating the development of novel agents.
• Rhenium clusters (Na₂H₁₄[{Re₆Q₈}(P(C₂H₄COO)₃)₆]) show potential as X-ray contrast agents but possess high toxicity due to their charge.

Purpose of the Study:

• To reduce the toxicity of rhenium clusters for use as X-ray contrast agents.
• To evaluate the efficacy of PEGylation as a strategy to mitigate the toxicity of rhenium clusters.

Main Methods:

• PEGylation of rhenium clusters using polyethylene glycol (PEG-400) in acidic aqueous media.
• Assessment of cytotoxicity against Hep-2 cells and acute toxicity in mice.
• Evaluation of the PEGylated compound for blood vessel visualization in rats using angiography and computed tomography.

Main Results:

• Successful binding of up to five carboxylate groups with PEG to the rhenium clusters.
• A twofold reduction in both cytotoxicity and acute toxicity was observed after PEGylation.
• The PEGylated rhenium clusters effectively visualized blood vessels in laboratory rats.

Conclusions:

• PEGylation is a successful strategy for reducing the toxicity of rhenium clusters.
• The modified rhenium clusters are promising candidates for safer X-ray contrast agents.
• The study demonstrates the potential of these agents for diagnostic imaging applications.