[Preparation and Evaluation of Fullerene Based Nanomedicine]

Fullerenes, large spherical molecules composed solely of carbon atoms, have gathered much attention for practical applications that take advantage of their unique spherical structure, physical properties, and biological activities. For example, fullerene C₆₀ can function as a photosensitizer, an antioxidant, a bioimaging agent, and as a gene or drug carrier. However, the practical use of C₆₀ for these potential biomedical applications has been hampered by the fact that it is only sparingly soluble in water. In this review, we focus on the development of hydrophilic C₆₀ nanoparticles, the surface of which is covered by cyclodextrin (CD), and then evaluate its biological activities. C₆₀/CD nanoparticles were stable under physiological conditions, and even under much harsher conditions. The nanoparticles generate reactive oxygen species (ROS) under visible light irradiation. Efficient photodynamic therapy against tumor growth was achieved by the intravenous injection of C₆₀/CD nanoparticles to tumor bearing mice, followed by photoirradiation. In addition, C₆₀(OH)₁₀, which is regarded as a potential candidate for use in scavenging ROS, was also prepared in the form of water soluble nanoparticles. C₆₀(OH)₁₀/CD nanoparticles protect the liver from injury by the suppression of oxidative stress occurring in the mitochondria, for example, by scavenging ROS such as superoxide anion radicals (O₂^・-), nitric oxide (NO) and peroxynitrite (ONOO^-), which act as critical mediators in liver injuries. C₆₀-based nanoparticles represent a potentially promising material for use in the treatment of cancer and oxidative stress-related diseases, and are promising as well in terms of extensive biological applications.