A Comprehensive Study of the Sc(III)-OPC2A-Fluoride Interaction: Equilibrium, Kinetics, and ⁴⁴Sc-Labeling.

Area of Science:

• Radiochemistry
• Coordination Chemistry
• Biomedical Applications

Background:

• Macrocyclic ligands are crucial for stable metal complexes in medicine.
• Scandium (Sc(III)) complexes offer potential for diagnostic and theranostic applications.

Purpose of the Study:

• To investigate the Sc(III)-OPC2A-F system for diagnostic and theranostic uses.
• To evaluate the stability and inertness of Sc(III) complexes with the OPC2A ligand.

Main Methods:

• Equilibrium studies to determine complex stability (log K).
• Decomplexation kinetic studies under varying pH conditions.
• Investigation of mixed-ligand complex formation and fluoride exchange kinetics.

Main Results:

• A stable [Sc(OPC2A)]+ complex formed (log K = 16.72(4)).
• The complex showed high stability in acidic conditions (t1/2 = 0.37 h in 1 M HCl) and exceptional stability at physiological pH.
• The [Sc(OPC2A)F] mixed complex exhibited remarkable stability (log K = 4.54(8)) and moderate inertness to fluoride exchange.
• [44Sc]Sc(III)-labeled complex formed rapidly and was stable in rat blood serum and against transmetalation/transchelation.

Conclusions:

• OPC2A is an excellent ligand platform for Sc(III) complexation.
• The Sc(III)-OPC2A complexes show high thermodynamic stability and kinetic inertness.
• These findings support the further investigation of Sc(III)-OPC2A complexes for in vivo biomedical applications.