Abstract

Magnetic resonance imaging (MRI) contrast agents play important roles in diagnosis and clinical applications. Particularly, superparamagnetic iron oxide nanoparticles (SNPs) with appropriate surface modification hold enormous promise as MRI contrast agents owning to their excellent biocompatibility. This thesis describes novel catechol-functionalized multidentate block copolymer (Cat-MDBC) strategy that enables the stabilization of SNPs with diameter ≤3.5 nm as effective MR bright imaging (T1-weighted) contrast agents.
Atom transfer radical polymerization and post-modification methods allow for the synthesis of well-controlled Cat-MDBCs. They enable the stabilization of ultrasmall SNPs with diameter ≈3.5 nm (i.e. USNPs) through a biphasic ligand exchange process. The results from surface characteristics, colloidal stability in physiological properties, relaxivity properties, and in vitro MRI suggest that the USNPs coated with Cat-MDBC (Cat-MDBC/USNPs) can be a promising candidate for T1-MRI application.
Further, extremely small SNPs with diameter ≈2 nm (i.e. ESNPs) coated with Cat-MDBC (Cat-MDBC/ESNPs) have better relaxivity properties as T1-MRI contrast agents, compared with the Cat-MDBC/USNP colloids; and more promisingly, they have the r2/r1 value comparable to clinically-used Gd3+-based contrast agents.