Iron–polyphenol dendritic complexes for regulating amplification of phenolic hydroxyl groups to improve magnetic resonance imaging

Abstract

Iron-based polyphenol complexes have been widely used as T1 contrast agents in tumor diagnosis. However, due to the irregularity of natural polyphenol ligand structures, it is challenging to determine the influence that the structures of ligands have on their T1 contrast properties. Herein, based on dendrimers, a series of polyphenol compounds (P1, P2, and P3) with simple and ordered structures were coordinated with iron (III) (Fe3+) to explore the effect that the structures of the polyphenols have on their T1 contrast performance. The new Fe3+-based polyphenol complexes based on the P1, P2, and P3 ligands with regular amplification of their phenolic hydroxyl groups exhibit increased longitudinal relaxivity (r1), due to the effective proton exchange generated by the hydrogen-bonding network between the phenolic hydroxyl groups and bound water. Moreover, the designed Fe3+-based polyphenol complexes exhibit good T1 contrast effect both in vitro and in vivo. Based on this, the relaxivity properties of Fe3+-based contrast agents may be improved by modifying their coordination structure, which could further facilitate the development of Fe3+-based complexes that exhibit excellent magnetic resonance imaging effect for disease diagnosis.