Synthesis and characterization of a new water-soluble endohedral metallofullerene for MRI contrast agents

Abstract Water-soluble amino acid derivatives of gadolinium (Gd) endohedral metallofullerenes (AAD-EMFs), Gd@C 82 O m (OH) n (NHCH 2 CH 2 COOH) l ( m  ≈ 6, n  ≈ 16 and l  ≈ 8) are synthesized by a direct reaction of the pure endohedral metallofullerene Gd@C 82 with an excess of alkaline solution of β-alanine. The structure of the AAD-EMFs is characterized by FTIR, XPS and laser-desorption time-of-flight (LD-TOF) mass spectrometries. Water proton relaxivity analysis indicates that the longitudinal relaxivity R 1 (the effect on 1/ T 1 , 9.1 mM −1  s −1 ) of AAD-EMFs is higher than that of the commercial MRI contrast agent, Magnevist (gadolinium-diethylenetriaminepentaacetic acid, Gd-DTPA, 5.6 mM −1  s −1 ). The MRI phantom studies are performed to confirm the high efficiency of this sample as MRI contrast agents.