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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.

Several Zn (II) and Al (III) phthalocyanines bearing eight or sixteen positive charges on substituents of different structure have been prepared. Synthesized polycationic phthalocyanines have been studied in aqueous and alcoholic media by UV-vis spectroscopy and tested for their efficacy in singlet oxygen photosensitization. It has been found that a minor structural modification at the periphery of the photosensitizer allows control over its key features such as singlet oxygen generation due to specific intermolecular interactions in solution. The efficacy of polycationic phthalocyanines to sensitize tryptophan photobleaching in aqueous media and inactivation of bacteria in sewage water is also structure-dependent. Among the complexes studied, two dyes - zinc octakis(pyridiniomethyl)- and octakis[ N -(2-hydroxyethyl)- N , N -dimethylammoniomethyl]substituted phthalocyanines - are the best sensitizers and have high potential for photodynamic applications.

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