On-Bead Combinatorial Synthesis and Imaging of Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Agents To Identify Factors That Influence Water Exchange

• Published in: Journal of the American Chemical Society Vol. 133; no. 33; pp. 13023 - 13030
• Main Authors: Napolitano, Roberta, Soesbe, Todd C, De León-Rodríguez, Luis M, Sherry, A. Dean, Udugamasooriya, D. Gomika
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.08.2011
• Subjects: Amines; Combinatorial Chemistry Techniques; Contrast Media - chemical synthesis; Contrast Media - chemistry; Magnetic Resonance Imaging; Peptides; Small Molecule Libraries - chemical synthesis; Water - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja201123f

The sensitivity of magnetic resonance imaging (MRI) contrast agents is highly dependent on the rate of water exchange between the inner sphere of a paramagnetic ion and bulk water. Normally, identifying a paramagnetic complex that has optimal water exchange kinetics is done by synthesizing and testing one compound at a time. We report here a rapid, economical on-bead combinatorial synthesis of a library of imaging agents. Eighty different 1,4,7,10-tetraazacyclododecan-1,4,7,10-tetraacetic acid (DOTA)-tetraamide peptoid derivatives were prepared on beads using a variety of charged, uncharged but polar, hydrophobic, and variably sized primary amines. A single chemical exchange saturation transfer image of the on-bead library easily distinguished those compounds having the most favorable water exchange kinetics. This combinatorial approach will allow rapid screening of libraries of imaging agents to identify the chemical characteristics of a ligand that yield the most sensitive imaging agents. This technique could be automated and readily adapted to other types of MRI or magnetic resonance/positron emission tomography agents as well.