Peptide derivatized lamellar aggregates as target-specific MRI contrast agents

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Biomedical Imaging

Background:

• Development of novel supramolecular aggregates for advanced applications.
• Combining stable gadolinium complexes with bioactive peptides for functional materials.

Purpose of the Study:

• To characterize the structural behavior and relaxivity of new supramolecular aggregates.
• To investigate aggregates formed from (C18)(2)DTPAGlu-Gd and DSPE-PEG(2000)-CCK8.
• To evaluate the in vitro target selectivity of CCK-8 peptide-containing aggregates.

Main Methods:

• Synthesis and combination of two amphiphilic monomers: (C18)(2)DTPAGlu-Gd and DSPE-PEG(2000)-CCK8.
• Structural characterization using Small-Angle Neutron Scattering (SANS) and Cryo-Transmission Electron Microscopy (Cryo-TEM).
• Proton relaxivity measurements and in vitro target selectivity assays using nuclear medicine techniques.

Main Results:

• Lamellar aggregates (80-100 Å thickness) formed with up to 50% (C18)(2)DTPAGlu-Gd.
• Transition to rod-like micelles (40 Å radius, >200 Å length) observed with increased (C18)(2)DTPAGlu-Gd.
• Consistent proton relaxivity (17.2 mM⁻¹s⁻¹) for both aggregate types, with varying local/global contributions.
• Demonstrated in vitro target selectivity for aggregates containing the CCK-8 peptide.

Conclusions:

• Successful formation of distinct supramolecular structures (lamellar aggregates and micelles) from defined amphiphilic monomers.
• Identical proton relaxivity values suggest robustness of the gadolinium complex's performance across different aggregate morphologies.
• The CCK-8 peptide confers target selectivity, indicating potential for these aggregates in targeted biomedical imaging.