Partition of rose bengal anion from aqueous medium into a lipophilic environment in the cell envelope of Salmonella typhimurium: Implications for cell-type targeting in photodynamic therapy

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 1989-11, Vol.4 (2), p.171-184
• Main Authors: Dahl, Thomas A., Valdes-Aguilera, Oscar, Midden, W.Robert, Neckers, D.C.
• Format: Article
• Language: English
• Subjects: bacterial cell membrane; bacterial cell wall; Binding Sites; Biological and medical sciences; Cell Membrane - metabolism; fluorescence; Fundamental and applied biological sciences. Psychology; Interactions. Associations; Intermolecular phenomena; lipopolysaccharide; Molecular biophysics; Phototherapy; Radiation-Sensitizing Agents - metabolism; Rose Bengal; Rose Bengal - metabolism; Salmonella bacteria; Salmonella typhimurium - metabolism; Salmonella typhimurium - radiation effects; Spectrometry, Fluorescence; Targeted photodynamic action; Water
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/1011-1344(89)80003-X

Photodynamic therapy employs photosensitizers for the selective destruction of tumor tissue while sparing the surrounding healthy tissue. Photosensitization may also be applied to the selective eradication of micro-organisms. Photosensitized inactivation requires that the sensitizer bind to the target and therefore the factors that determine photosensitizer binding are critical to photosensitization selectivity. This paper reports the determination of some features of the binding site of the potent photosensitizer, Rose Bengal, in Salmonella bacteria and describes some of the factors that affect this binding. The shift in the wavelength of maximum fluorescence and experiments with the fluorescence quencher TNBS indicate that Rose Bengal is located in a non-aqueous compartment such as the outer membrane. The dye does not seem to significantly accumulate inside the cell, but rather to accumulate in the outer membrane. Time-dependent changes in sensitizer localization in two strains of Salmonella typhimurium that differ in cell wall formation, LT-2 and TA1975, correspond to their differences in susceptibility to photosensitized killing. Therefore these results provide clues to the factors that determine photosensitization selectivity. Understanding this phenomenon is essential for the efficient design of selective photosensitizers and for optimizing antitumor and antiviral photodynamic therapy.