Encapsulation of Gadolinium Oxide Nanoparticle (Gd₂O₃) Contrasting Agents in PAMAM Dendrimer Templates for Enhanced Magnetic Resonance Imaging in Vivo

There has been growing interest in the research of nanomaterials for biomedical applications in recent decades. Herein, a simple approach to synthesize the G4.5-Gd 2 O 3 -poly(ethylene glycol) (G4.5-Gd 2 O 3 -PEG) nanoparticles (NPs) that demonstrate potential as dual ( T 1 and T 2 ) contrasting agents in magnetic resonance imaging (MRI) has been reported in this study. Compared to the clinically popular Gd-DTPA contrasting agents, G4.5-Gd 2 O 3 -PEG NPs exhibited a longer longitudinal relaxation time ( T 1 ) and better biocompatibility when incubated with macrophage cell line RAW264.7 in vitro . Furthermore, the longitudinal relaxivity ( r 1 ) of G4.5-Gd 2 O 3 -PEG NPs was 53.9 s –1 mM –1 at 7T, which is equivalent to 4.8 times greater than to the Gd-DTPA contrasting agents. An in vivo T 1 -weighted MRI results revealed that G4.5-Gd 2 O 3 -PEG NPs significantly enhanced signals in the intestines, kidney, liver, bladder, and spleen. In addition, the T 2 -weighted MRI results revealed darker contrast in the kidney, which proves that G4.5-Gd 2 O 3 -PEG NPs can be exploited as T 1 and T 2 contrasting agents. In summary, these findings suggest that the G4.5-Gd 2 O 3 -PEG NPs synthesized by an alternative approach can be used as dual MRI contrasting agents.