An ultra-sensitive T 2 -weighted MR contrast agent based on Gd 3+ ion chelated Fe 3 O 4 nanoparticles.

An ultra-sensitive T 2 -weighted MR imaging contrast agent was prepared based on Fe 3 O 4 nanoparticles and Gd 3+ ions (Fe 3 O 4 @Gd). Amino modified Fe 3 O 4 nanoparticles were conjugated to diethylenetriamine pentaacetic acid, and finally coordinated with Gd 3+ ions. The nanoparticles had a uniform morphology with a size of 100 nm and a Gd/Fe mass ratio of 1/110. The r 2 (transverse relaxivity) of the Fe 3 O 4 nanoparticles increased from 131.89 mM -1 s -1 to 202.06 mM -1 s -1 after coordination with Gd 3+ ions. MR measurements showed that the aqueous dispersion of Fe 3 O 4 @Gd nanoparticles had an obvious concentration-dependent negative contrast enhancement. Hepatoma cells were selected to test the cytotoxicity and MR imaging effect. The application of Fe 3 O 4 @Gd nanoparticles as contrast agents was also exploited in vivo for T 2 -weighted MR imaging of rat livers. All the results showed the effectiveness of the nanoparticles in MR diagnosis.