The properties of an ideal photosensitizer are water solubility, low cytotoxicity in the dark, high ability to produce reactive oxygen species (ROS). The characteristics of water-soluble fullerene (C60) amino acid nanoparticles as a photosensitizer were evaluated. C60 modified with l-phenylalanine (C60-phe) or glycine (C60-gly) was very efficient to carry out photodynamic activity leading to cleavage of plasmid DNA in vitro. These C60 amino acid nanoparticles were the most active photosensitizer against human Liver cancer cells and induced cancer cells apoptosis after illumination. However, these derivatives exhibited no significant cytotoxicity in dark. It produced diffuse intracellular fluorescence when 2',7'-dichlorfluorescein-diacetate (DCFH-DA) was added as an ROS probe, suggesting phototoxicity of these derivatives related with the generation of intracellular ROS. These findings indicate that these fullerene derivatives may be excellent candidate PDT enhancing agents.
