Diethylenetriaminepentaacetic acid-gadolinium (DTPA-Gd)-conjugated polysuccinimide derivatives as magnetic resonance imaging contrast agents

Biocompatible polysuccinimide ( PSI) derivatives conjugated with diethylenetriaminepentaacetic acid gadolinium ( DTPA- Gd) were prepared as magnetic resonance imaging ( MRI) contrast agents. In this study, we synthesized PSI derivatives incorporating methoxy- poly( ethylene glycol) ( mPEG) as hydrophilic ligand, hexadecylamine as hydrophobic ligand, and DTPA- Gd as contrast agent. PSI was synthesized by the polycondensation polymerization of aspartic acid. All the synthesized materials were characterized by proton nuclear magnetic resonance ( H-1 NMR). Critical micellization concentrations were determined using fluorescent probes ( pyrene). Micelle size and shape were measured by electro- photometer light scattering ( ELS) and atomic force microscopy ( AFM). The formed micelle size ranged from 100 to 300 nm. The T1- weighted MR images of the phantom prepared with PSI-mPEG-C-16-( DTPA- Gd) were obtained in a 3.0 T clinical MR imager, and the conjugates showed a great potential as MRI contrast agents.