Study of rare earth encapsulated carbon nanomolecules for biomedical uses

Gd@C82(OH)40 has been proposed to be as a new generation of the magnetic resonance imaging (MRI) contrast agent, but water-soluble fullerenols Gd@C82(OH)n with n > 36 can easily lead to open-caged structures of a high instability. This restricts the practical bio-uses of Gd-metallofullerenols with a large number of hydroxyl groups. To explore how the imaging efficiency varies with decreasing hydroxyl number in Gd@C82(OH)n of a good stability in vivo, Gd@C82(OH)22 was prepared, characterized and its imaging efficiency in mice was studied. This work aims at searching a chemical form of water-soluble Gd-metallofullerenols that satisfy both requirements of the good stability and high imaging efficiency in vivo. The results indicate that the proton relaxivity of Gd@C82(OH)22 is lower than that of Gd@C82(OH)40, but still higher than the commercial Gd-DTPA MRI contrast agent.