Cationic Fullerenes Are Effective and Selective Antimicrobial Photosensitizers

Abstract

Fullerenes are soccer ball-shaped molecules composed of carbon atoms, and, when derivatized with functional groups, they become soluble and can act as photosensitizers. Antimicrobial photodynamic therapy combines a nontoxic photosensitizer with harmless visible light to generate reactive oxygen species that kill microbial cells. We have compared the antimicrobial activity of six functionalized C(60) compounds with one, two, or three hydrophilic or cationic groups in combination with white light against gram-positive bacteria, gram-negative bacteria, and fungi. After a 10 min incubation, the bis- and tris-cationic fullerenes were highly active in killing all tested microbes (4-6 logs) under conditions in which mammalian cells were comparatively unharmed. These compounds performed significantly better than a widely used antimicrobial photosensitizer, toluidine blue O. The high selectivity and efficacy exhibited by these photosensitizers encourage further testing for antimicrobial applications.

Photodynamic therapy with fullerenes

“…In two recent reports 44,45 we studied the photosensitizer properties of two series of three functionalized fullerene compounds, one series with polar diserinol groups (BF1-BF3), and a second series of three compounds with quaternary pyrrolidinium groups (BF4-BF6) (Fig. 3).…”

Antibacterial photodynamic therapy: overview of a promising approach to fight antibiotic-resistant bacterial infections

“…Fullerenes must be chemically modified with amphiphilic molecules [75] to enable bacterial photosensitization. It has been demonstrated that the derivatization translates to high selectivity towards bacterial cells [59]. Accordingly, a cationic fullerene derivative N,N-dimethyl-2-(40-N,N,N-trimethylaminophenyl)fulleropyrrolidinium iodide (DTC60 2+ ) [74] considerably enhanced APDT efficacy of E. coli and Pseudomonas aeruginosa (> 3.5 log) compared to the negligible killing effect with non-charged N-methyl-2-(40-acetamidophenyl) fulleropyrrolidine (MAC 60 ).…”

“…Spheroidal fullerenes such as C60 [59] and C70 [60] (Table 1) are football-like structures composed of pentagonal and hexagonal rings that can absorb visible light [61] and mediate photochemical reactions from the excited state [60,[62][63][64]. The photo-excited fullerenes can react with electron donors to generate fullerene radical anions (C60…”

All you need is light

“…2). 25,26 These include halogenated xanthenes, such as Rose Bengal (RB), 27 perylenequinones, such as hypericin 28 phenothiazinium salts, such as toluidine blue O (TBO) and methylene blue (MB), 29 cationic buckminsterfullerenes (e.g., C 60 ), 30,31 psoralens (furanocoumarins).…”