| Summary: | The water proton spin relaxivity, colloidal stability, and biocompatibility of nanoparticle-based magnetic resonance imaging (MRI) contrast agents depend on the surface-coating ligands. Here, poly(acrylic acid-co-maleic acid) (PAAMA) (M<sub>w</sub> = ~3000 amu) is explored as a surface-coating ligand of ultrasmall gadolinium oxide (Gd<sub>2</sub>O<sub>3</sub>) nanoparticles. Owing to the numerous carboxylic groups in PAAMA, which allow its strong conjugation with the nanoparticle surfaces and the attraction of abundant water molecules to the nanoparticles, the synthesized PAAMA-coated ultrasmall Gd<sub>2</sub>O<sub>3</sub> nanoparticles (d<sub>avg</sub> = 1.8 nm and a<sub>avg</sub> = 9.0 nm) exhibit excellent colloidal stability, extremely low cellular toxicity, and a high longitudinal water proton spin relaxivity (r<sub>1</sub>) of 40.6 s<sup>−1</sup>mM<sup>−1</sup> (r<sub>2</sub>/r<sub>1</sub> = 1.56, where r<sub>2</sub> = transverse water proton spin relaxivity), which is approximately 10 times higher than those of commercial molecular contrast agents. The effectiveness of PAAMA-coated ultrasmall Gd<sub>2</sub>O<sub>3</sub> nanoparticles as a T<sub>1</sub> MRI contrast agent is confirmed by the high positive contrast enhancements of the in vivo T<sub>1</sub> MR images at the 3.0 T MR field.
|
|---|
