Antimicrobial photoinactivation with functionalized fullerenes

Photodynamic therapy (PDT) is based on the interaction between light and a nontoxic photosensitizer to produce a long-lived triplet state that reacts in the presence of oxygen, generating reactive oxygen species (ROS) through a type I reaction, or generating singlet oxygen through a type II reaction. Porphyrins and their derivatives were the first compounds to be used as photosensitizers, however, a great number of different molecules have since been shown to be effective in PDT, including fullerenes. The first fullerene, C₆₀, was discovered in 1985, and since then the unique properties of these compounds have attracted the attention of researchers in the biomedical area. Due to their extended ?-conjugation, they can absorb light in the UV and visible spectrum, and can generate ROS, especially in the presence of electron donors (mainly through a type I reaction, generating superoxide anion). The functionalization of fullerenes, in order to enhance their solubility in aqueous media and their absorption in the visible spectrum, has increased the range of biomedical applications of these compounds, and promising results have been published regarding antitumor and antimicrobial PDT in vitro and in vivo. This chapter covers the most relevant studies using functionalized fullerenes in antimicrobial photodynamic inactivation.