Masahito Mikawa

Syntheses and EELS characterization of water-soluble multi-hydroxyl Gd@C82 fullerenols

Abstract Various water-soluble multi-hydroxyl fullerenes (fullerenols), C60(OH)n, C70(OH)n and C84(OH)n, and a Gd metallo-fullerenols, Gd@C82(OH)n have been synthesized by the Kitazawa method. Elementary chemical analyses indicate that all of these fullerenols have 30–40 hydroxyl groups and 11–15 coordinated water molecules via hydrogen bonds. Electron energy loss spectroscopy (EELS) on Gd@C82 fullerenols shows that the π ∗ peak area in the C K-edge spectra decreases on going from intact Gd@C82 metallofullerene to Gd@C82 fullerenols, indicating an increase in sp3 character of the fullerenols. Furthermore, Gd M4,5-edge EELS spectra show that the encapsulated Gd atom has a trivalent Gd3+ state.

An intelligent MRI contrast agent for tumor sensing.

An intelligent MRI contrast agent has been designed by taking advantage of a microenvironmental responsive polyion complex (PIC). The intelligent signal switching was achieved by controlling Gd ion-water interactions in the microenvironmental responsive PIC. MRI signal of the agent appeared only in tumor region, selectively, and did not appear in normal tissues, when the agent was administrated to a tumor-bearing mouse from the tail vein. The acidic microenvironment, such as lower extracellular fluid pH, higher expression of acidic proteins and polysaccharides, was suggested to cause the tumor-selective activation of the agent.