Therapeutic applications of low-toxicity spherical nanocarbon materials

Nanocarbon materials have received considerable attention due to their unique structure and properties, which make them promising candidate materials for use in biomedical applications. In this review, we discuss the therapeutic applications of spherical nanocarbon materials, including fullerene nanoparticles, carbon nanohorn aggregates, nanodiamonds and porous carbon nanospheres, and their toxicology in biological systems. We put special emphasis on the antitumor effects of these multifunctional nanoparticles, which operate via novel mechanisms in a highly efficient manner. The low toxicities of these spherical nanocarbon materials as well as the possible effects of shape on toxicity are discussed. Various spherical nanocarbon materials, including fullerenes, carbon nanohorn aggregates, nanodiamonds etc., have shown potential anti-cancer effects. Fullerenes and metallofullerenes possess outstanding ROS-scavenging capability, as well as other biological effects like immunity enhancement etc., affording promising tumor suppression potential. Carbon nanohorn aggregates and nanodiamond particles have demonstrated effective drug delivery ability for cancer therapy. Moreover, it is noteworthy that these spherical nanocarbon materials show positive toxicological evaluation results, encouraging possible practical usage for biomedical applications. Since the discovery of fullerenes in 1985 with the report of a football-shaped C60 molecule, a variety of carbon nanostructures have emerged, the most familiar of which are carbon nanotubes and graphene sheets. Owing to some intriguing properties and an ever-increasing range of potential applications, these ‘nanocarbons’ have attracted a great deal of attention from the scientific and technology communities. Jianxun Xu and Yuliang Zhao from the National Center for Nanosciences and Technology, China, and co-workers review both the pharmaceutical activity and toxicity of spherical nanocarbons. Such materials—which include fullerenes, the ‘nanohorn’ clusters formed from aggregated horn-shaped carbon nanotubes, nanodiamonds and porous nanospheres—are less toxic than their non-spherical counterparts in biomedical applications. In particular, Xu, Zhao and colleagues focus on the potential of these species for anticancer treatments that arise from their effects, including tumor metastasis and drug-resistance suppression.