Polyethylene glycol-cover ultra-small Gd2O3 nanoparticles for positive contras at 1.5 T magnetic resonance clinical scanning

• Published in: Nanotechnology Vol. 18; no. 39; p. 395501
• Main Authors: Fortin, Marc-André, Petoral Jr, Rodrigo M., Söderlind, Fredrik, Klasson, Anna, Engström, Maria, Veres, Teodor, Käll, Per-Olov, Uvdal, Kajsa
• Format: Journal Article
• Language: English
• Published: 2007
• Subjects: NATURAL SCIENCES; NATURVETENSKAP
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/18/39/395501

The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd 2 O 3 ) were studied, and the impact of polyethylene glycol capping on the relaxivity constants ( r 1 , r 2 ) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd 2 O 3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd 2 O 3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd 3+ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG–Gd 2 O 3 and PEG-silane–SPGO (Gd 2 O 3 ,< 40 nm diameter). The small and narrow size distribution of US-Gd 2 O 3 was confirmed with TEM (~3 nm) and DLS. PEG-silane–US-Gd 2 O 3 relaxation parameters were twice as high as for Gd–DTPA and the r 2 / r 1 ratio was 1.4. PEG-silane–SPGO gave low r 1 relaxivities and high r 2 / r 1 ratios, less compatible with positive contrast agent requirements. Higher r 1 were obtained with PEG-silane in comparison to DEG–Gd 2 O 3 . Treatment of DEG–US-Gd 2 O 3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd 2 O 3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.