A fullerene copolymer that is highly water soluble could find use in photodynamic therapy. 

Fullerene-based materials have been shown to have powerful light-induced biological activity, with a high quantum yield of reactive oxygen species. For this reason, they are regarded as potentially useful in photodynamic therapy, a non-invasive light-based cancer treatment. But so far, the poor solubility in water of the C₆₀ molecule has been a major obstacle to its use in biological applications.

Yoko Yamakoshi and Yuko Iwamoto at the University of California at Santa Barbara, US, have made highly water soluble C₆₀-derived polymers, based on the non-toxic poly(vinylpyrrolidone). 

'We achieved highest level of fullerene solubility in water yet reported.even higher in concentration than saturated C₆₀ solution in toluene,' said Yamakoshi.

The molecular weight of the polymers is also in the right range to accumulate in tumour tissue, known as the enhanced permeation and retention (EPR) effect. 

Yamakoshi says that these properties, combined with the ability to generate reactive oxygen species, mean that the C₆₀ copolymers could have great potential as reagents for photodynamic therapy.

Nicola Nugent