Polaron Activation in Conjugated Polymers for Enhanced T2 MRI Contrast

Abstract

Magnetic Resonance Imaging (MRI) typically relies on metal-based contrast agents to enhance tissue visibility, but these agents raise safety concerns. Conjugated polymers present a promising organic alternative, generating T2 MRI contrast through the presence of unpaired organic electrons, known as polarons. However, the low polaron content limits the imaging capabilities of conjugated polymer-based MRI agents. This study explores strategies for effectively enhancing T2 MRI contrast in polypyrrole nanoparticles by increasing polaron content and optimizing interactions with water protons. Our results demonstrate that active polarons can be promoted by altering oxidative polymerization conditions. Furthermore, we observe a trade-off between polaron content and its interactions with water protons. This work investigates the underlying mechanisms by which structural parameters affect T2 MRI contrast, providing a clearer understanding of how to improve the imaging capabilities of conjugated polymer-based MRI agents.