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Title: Photodynamic inactivation of a Gram (-) bacterium (Escherichia coli) by Zn(II) N-alkylpyridyl-porphyrins
Authors: مريم مبارك عبدالكريم ملا عواد 
Supervisor: د.ليدميل بينوف
Keywords: Photosensitizer Photodynamic therapy Hematoporphyrin;Infrared;Photodynamic inactivation
Issue Date: 2012
Publisher:  Kuwait university - college of graduate studies
Abstract: Photodynamic therapy (PDT) is an efficient way to destroy tumor and bacterial cells. It is based on the use of a light-absorbing compound (photosensitize) and visible light irradiation. In the presence of molecular oxygen, light activation of the photosensitizer leads to the local production of singlet oxygen and other reactive oxygen species that damage and kill the targeted cells. Lately there has been active research on new photosensitizers since finding a suitable photosensitizer is crucial in improving the efficacy of PDT. Zn(II) N-alkylpyridyl-porphyrins (ZnPs) can act as photosensitizers and can kill antibiotic-resistant pathogenic bacteria. The aim of this study was to compare the efficiency of cationic ZnPs with different peripheral substituents on the photodynamic inactivation of a Gram (-) bacterium (Escherichia coli) and to perform some preliminary investigations on the mechanism of ZnP antibacterial action. We investigated the effect of ZnPs (the cationic ortho-, meta-, and para-isomers of ZnTMPyP, ZnTnBu-2-PyP, ZnTnHex-2-PyP, and the anionic ZnTBAP) on bacterial cell growth, viability, metabolism and membrane integrity. Photosensitizer-mediated generation of singlet oxygen, ATP leakage and DNA damage were also investigated. Upon exposure to illumination, ZnPs caused inhibition of bacterial growth; inactivated key metabolic enzymes and damaged the cell envelope. These effects finally lead to cell death. There was no detectable major structural DNA alteration. None of these effects were observed when the cells were incubated with ZnPs in the dark. These results show that ZnPs have a potential for photodynamic therapy and indicate that the ZnPs differ in their efficiency in bacterial killing due to their position in the aliphatic chain which in turn affects their hydrophobicity. We found that the most hydrophobic ZnP, (ZnTnHex-2-PyP), was the most efficient in killing, while the least efficient was ZnTM-2-PyP.
Appears in Programs:0540 Medical Biochemistry (M.Sc.)

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