Synthesis, Characterization, and Magnetic Resonance Evaluation of Polyglycerol-Functionalized Detonation Nanodiamond Conjugated with Gadolinium(III) Complex

A nanodiamond-polyglycerol-gadolinium(III) conjugate has been designed and prepared as novel nanodiamond-based magnetic resonance (MR) contrast agent dispersible in physiological media. Detonation nanodiamond (dND) was first grafted with polyglycerol (PG) through ring-opening polymerization of glycidol to impart dispersibility to dND in physiological media. Since the hydroxyl group in PG serves as a scaffold for further surface functionalization, diethylenetriaminepentaacetic acid (DTPA) was immobilized on the surface of dND-PG through multistep organic transformations and Gd(III) ion was complexed in the last step. The resulting dND-PG-Gd(III) exhibited good dispersibility (>4.5 mg/mL) and stability (>3 months) in phosphate buffered saline (PBS). In vitro MR evaluation indicates that water proton T-1 relaxivity or r(1) of dND-PG-Gd(III) in aqueous solutions is larger than that of Magnevist and the difference in the relaxivity becomes larger under weaker magnetic fields. The good dispersibility together with relatively high T-1 relaxivity makes dND-PG-Gd(III) a promising contrast agent for in vivo MR imaging.