Sonodynamically-induced anticancer effects by functionalized fullerenes.

Background: Functionalized fullerenes, such as polyhydroxy fullerenes (PHF), have attracted particular attention due to their water solubility and their potential application in tumor imaging and therapy as carbon nanomaterials. In this study, the sonodynamically-induced antitumor effect of PHF was investigated. Materials and Methods: Sonodynamically-induced antitumor effects of PHF in combination with ultrasound were investigated using isolated sarcoma 180 cells and solid tumor from colon 26 carcinoma cells. Results: The cell damage induced by sonication was enhanced by two-fold in the presence of 80 μM PHF. Histidine significantly inhibited this enhancement. This inhibitory effect suggests that the sonodynamically- induced antitumor effect was mediated by sonodynamically- generated reactive oxygen species. The combined treatment of ultrasonic exposure with PHF suppressed the growth of implanted colon 26 tumors. The destruction of tumor tissue was observed with the ultrasonic treatment in combination with PHF, while neither the treatment with PHF alone nor that with ultrasound alone caused necrosis. Conclusion: These results suggest that PHF is a potential sonosensitizer for sonodynamic treatment of solid tumors. Ultrasound has an appropriate tissue attenuation coefficient for penetrating intervening tissues to reach non-superficial objects while maintaining the ability to focus energy into small volumes. This is a unique advantage when compared to electromagnetic modalities such as laser beams in the application to non-invasive treatment of non-superficial tumors. Although the use of ultrasound for tumor treatment