Functionalized Fullerenes in Photodynamic Therapy

Since the discovery of C₆₀ fullerene in 1985, scientists have been searching for biomedical applications of this most fascinating of molecules. The unique photophysical and photochemical properties of C₆₀ suggested that the molecule would function well as a photosensitizer in photodynamic therapy (PDT). PDT uses the combination of non-toxic dyes and harmless visible light to produce reactive oxygen species that kill unwanted cells. However the extreme insolubility and hydrophobicity of pristine C₆₀, mandated that the cage be functionalized with chemical groups that provided water solubility and biological targeting ability. It has been found that cationic quaternary ammonium groups provide both these features, and this review covers work on the use of cationic fullerenes to mediate destruction of cancer cells and pathogenic microorganisms in vitro and describes the treatment of tumors and microbial infections in mouse models. The design, synthesis, and use of simple pyrrolidinium salts, more complex decacationic chains, and light-harvesting antennae that can be attached to C₆₀, C₇₀ and C₈₄ cages are covered. In the case of bacterial wound infections mice can be saved from certain death by fullerene-mediated PDT.