Aggregate of gadofullerenols base on the number of hydroxys bonded carbon cage

Water-soluble derivatives of endohedral metallofullerenes possess unique potential for medicinal applications, since the fullerene cage protects the encapsulated metal ion from externally chemical attack, which reduces the release possibility of the highly toxic metallic ion in the body. The fullerene derivatives have enabled many biologically relevant studies of diverse compounds that have potential uses for biologic medicine. But one of the key issues that encumber these applications is the aggregation phenomena of hydrophobic molecules in aqueous or, more general, polar media. Biological tests performed on water-soluble fullerene derivatives have shown the results to be strongly affected by aggregation. Aqueous solution of hydroxyl metallofullerene Gd doped C82(OH)x consists of a Gd doped C82 cage covalently bonded with volatile numbers of the hydroxyl. In order to slove this important issue, we use synchrotron radiation small angle X-ray scattering to study aggregation of Gd doped C82(OH)x with different numbers of hydroxyl in polar solution of different pH values. The results revealed that aggregate state of gadofullerenols is related with the number of hydroxyl bonded on the carbon cage. When the number of hydroxyl is varying from 44 to 18, the average hydrodynamic diameters for the aggregates vary from 10 to 40 nm. Interestingly, this variation shows a pH value dependence, which are demonstrated by the further observation of AFM techniques.