Photophysical properties and photodynamic activity of octacationic oxotitaniumiv phthalocyanines

Abstract

The photophysical and photosensitizing properties of two octacationic oxotitanium phthalocyanines (TiOPcs), bearing pyridiniomethyl or cholinyl substituents, have been studied in aqueous and alcohol solutions. In water, both compounds were monomeric with the high quantum yields of fluorescence (Phi(F) = 0.17-0.19) and singlet oxygen formation (Phi(Delta) = 0.4-0.5). The Phi(F) and Phi(Delta) of both phthalocyanines decreased with the increase of solvent hydrophobicity from water to ethanol. This effect was much stronger in alcohol solutions of the pyridiniomethyl-substituted phthalocyanine and probably results from aggregation of TiOPc molecules caused by association of chloride anions with phthalocyanine cationic groups. Evidence is presented that under illumination aqueous TiOPc solutions also produce hydroxyl radicals, which probably appear owing to photocleavage of water molecules. The quantum yield of OH formation was (3-5) x 10(-5) after argon purging and twice as much in the presence of air. It is shown that irradiation of TiOPc solutions causes photobleaching of TiOPcs. The photobleaching quantum yield in water was found to be about 1 x 10(-4). The data suggest that photobleaching occurs owing to the reactivity of hydroxyl radicals, though singlet oxygen is generated by TiOPcs much more efficiently. The phototoxicity of the tested TiOPcs toward bacteria has been revealed. It is proposed that both OH and (1)O(2) might be responsible for the observed bactericidal effects.

Effect of a spacer on phthalocyanine functionalized cellulose nanofiber mats for decolorizing reactive dye wastewater

“…The reactive species produced by MPcs during catalytic oxidation have been studied and free hydroxyl radicals (Tao et al 2001(Tao et al , 2002Kuznetsova et al 2009), singlet oxygen (Kluson et al 2008a) or the metal-peroxo complex (Sorokin et al 1995(Sorokin et al , 1996 were suggested. As a first step in elucidating the reactive species responsible for reactive red X-3B degradation, we carried out a catalytic oxidation experiment in the presence of isopropanol, an effective •OH radical scavenger (Smith et al 2004;Mrowetz and Selli 2005;Salem et al 2009;Yang et al 2009), to inhibit catalytic oxidation mediated by •OH radicals.…”

Photodynamic therapy induces an immune response against a bacterial pathogen

“…Ideally PDT should prevent the regrowth of the pathogens after the treatment [93]. Many studies aimed to optimize these compounds to improve the selectivity for microbial cells over host mammalian cells [94], maximizing absorption in the near infrared regions of the spectrum [95] and reducing photobleaching [96]. Phenothiazinium dyes such as toluidine blue O and methylene blue [97–99] and azure dyes [100] have been widely tested and employed in PDT against Gram-positive, Gram-negative and fungal cells.…”

Photodynamic therapy for infections: Clinical applications

“…The PS that are commonly used in antimicrobial therapy in vitro include a very wide range of compounds most of which are cationic 18. Considerable effort has been put into optimizing many of these compounds in areas such as selectivity for microbial cells over host mammalian cells 19, maximizing absorption in far‐red and near infrared regions of the spectrum 20 and reducing photobleaching 21. These have proven to be very effective in vitro and in vivo in animal models of infection, but most of these PS are yet to be tested in the clinical trials.…”