In vitro and in vivo imaging studies of a new endohedral metallofullerene nanoparticle.

Purpose: To evaluate the effectiveness of a functionalized trimetallic nitride endohedral metallofullerene nanoparticle as a magnetic resonance (MR) imaging proton relaxation agent and to follow its distribution for in vitro agarose gel infusions and in vivo infusions in rat brain. Materials and Methods: The animal study was approved by the animal care and use committee. Gd3N@C80 was functionalized with poly(ethylene glycol) units, and the carbon cage was hydroxylated to provide improved water solubility and biodistribution. Relaxation rate measurements (R1 = 1/T1 and R2 = 1/T2) of water solutions of this contrast agent were conducted at 0.35-, 2.4-, and 9.4-T MR imaging. Images of contrast agent distributions were produced following infusions in six agarose gel samples at 2.4 T and from direct brain infusions into normal and tumor-bearing rat brain at 2.4 T. The relaxivity of a control functionalized lutetium agent, Lu3N@C80, was also determined. Results: Water hydrogen MR imaging relaxivity (r1) for thi...