Electrostatic Binding of Substituted Metal Phthalocyanines to Enterobacterial Cells: Its Role in Photodynamic Inactivation

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M. G. Strakhovskaya^1*, Y. N. Antonenko², A. A. Pashkovskaya^2,3, E. A. Kotova², V. Kireev^1,4, V. G. Zhukhovitsky⁵, N. A. Kuznetsova⁶, O. A. Yuzhakova⁶, V. M. Negrimovsky⁶, and A. B. Rubin¹

¹Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-1115; E-mail: marstr@biophys.msu.ru

²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3181; E-mail: antonen@genebee.msu.ru

³Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia; E-mail: PashkovskaiaAA@yandex.ru

⁴Faculty of Natural Sciences, Vilnius University, ul. Churlionis 21/27, Vilnius, LT-03101, Lithuania

⁵Botkin Moscow City Clinical Hospital, 2-oi Botkinskii Pereulok 5, 125101 Moscow, Russia

⁶Organic Intermediates and Dyes Institute (NIOPIK), ul. B. Sadovaya 1/4, 123995 Moscow, Russia; fax: (495) 254-7015; E-mail: lab32@niopik.ru

^* To whom correspondence should be addressed.

Received February 25, 2009; Revision received May 20, 2009

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The effect of ionic substituents in zinc and aluminum phthalocyanine molecules and of membrane surface charge on the interaction of dyes with artificial membranes and enterobacterial cells, as well as on photosensitization efficiency was studied. It has been shown that increasing the number of positively charged substituents enhances the extent of phthalocyanine binding to Escherichia coli cells. This, along with the high quantum yield of singlet oxygen generation, determines efficient photodynamic inactivation of Gram-negative bacteria by zinc and aluminum octacationic phthalocyanines. The effect of Ca²⁺ and Mg²⁺ cations and pH on photodynamic inactivation of enterobacteria in the presence of octacationic zinc phthalocyanine has been studied. It has been shown that effects resulting in lowering negative charge on outer membrane protect bacteria against photoinactivation, which confirms the crucial role in this process of the electrostatic interaction of the photosensitizer with the cell wall. Electrostatic nature of binding is consistent with mainly electrostatic character of dye interactions with artificial membranes of different composition. Lower sensitivity of Proteus mirabilis to photodynamic inactivation, compared to that of E. coli and Salmonella enteritidis, due to low affinity of the cationic dye to the cells of this species, was found.

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KEY WORDS: photodynamic inactivation, photosensitizer, phthalocyanines, enterobacteria, lipopolysaccharides, fluorescence quenching, fluorescence correlation spectroscopy

DOI: 10.1134/S0006297909120025

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