Innovative cationic fullerenes as broad-spectrum light-activated antimicrobials

Abstract

Photodynamic inactivation (PDI) is a rapidly developing antimicrobial technology which combines a non-toxic photoactivatable dye or photosensitizer (PS) in combination with harmless visible light of the correct wavelength to excite the dye to its reactive triplet state that will then generate reactive oxygen species (ROS) that are highly toxic to cells. Buckminsterfullerenes are closed-cage molecules entirely composed of sp2 hybridized carbon atoms and although their main absorption is in the UV, they also absorb visible light and have a long-lived triplet state. When C60 fullerene is derivatized with cationic functional groups it forms molecules that are more water-soluble and can mediate PDT efficiently upon illumination, and moreover cationic fullerenes can selectively bind to microbial cells. In this report we describe the synthesis and characterization of several new cationic fullerenes. Their relative effectiveness as broad-spectrum antimicrobial photosensitizers against Gram-positive, Gram-negative bacteria, and a fungal yeast was determined by quantitative structure function relationships.

Biological applications of hydrophilic C60 derivatives (hC60s)− a structural perspective

“…More cationic charges were beneficial for binding microbial membrane with negative charges [62]. The further study corroborated this result: compound 7 (with 6 cations) > compound 6 (with 2 cations), two regioisomers 9 and 10 (with 2 cations) > compound 8 (with 1 cation); compound 13 (with 2 cations) > compound 12 (with 1 cation) > compound 11 (without cation) [63,64].…”

Nanodrug applications in photodynamic therapy

“…Fullerenes, although at the lower end of the nanoparticles scale (Ø 1 nm), have a high degree of photostability and produce more reactive oxygen species type I, such as superoxide or hydroxyl radicals, and have been shown to have increased selectivity for microbial cells over than mammalian cells and are now used in anti-microbial applications [75]. Likewise, Rose Bengal, one of the frequently used photosensitizers due to its high water solubility, high singlet oxygen quantum yield and low rate of photodegradation [76], is used in silica nanoparticles to inactivate gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and showed high efficiency in inactivating bacterial through photodynamic action [77].…”

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).…”