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A study of the uptake of toluidine blue O by Porphyromonas gingivalis and the mechanism of lethal photosensitization

Bhatti, M; MacRobert, A; Meghji, S; Henderson, B; Wilson, M; (1998) A study of the uptake of toluidine blue O by Porphyromonas gingivalis and the mechanism of lethal photosensitization. PHOTOCHEM PHOTOBIOL , 68 (3) 370 - 376.

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Abstract

The purpose of the study was to determine the distribution of the photosensitizer toluidine blue O (TBO) within Porphyromonas gingivalis and the possible mechanism(s) involved in the lethal photosensitization of this organism. The distribution of TBO was determined by incubating P, gingivalis with tritiated TBO (H-3-TBO) and fractionating the cells into outer membrane (OM), plasma membrane (PM), cytoplasmic proteins, other cytoplasmic constituents and DNA. The percentage of TBO in each of the fractions was found to be, 8.7, 5.4, 1.9, 5.7 and 0.3%, respectively. The involvement of cytotoxic species in the lethal photosensitization induced by light from a helium-neon (HeNe) laser and TBO was investigated by using deuterium oxide (D2O), which prolongs the lifetime of singlet oxygen, and the free radical and singlet oxygen scavenger L-tryptophan. There were 9.0 log(10) and 2 log(10) reductions in the presence of D2O and H2O (saline solutions), respectively, at a light dose of 0.44 J (energy density = 0.22 J/cm(2)), suggesting the involvement of singlet oxygen, Decreased kills were attained in the presence of increasing concentrations of L-tryptophan, The effect of lethal photosensitization on whole cell proteins was determined by measuring tryptophan fluorescence, which decreased by 30% using 4.3 J (energy density = 4.3 J/cm2) of light. Effects on the OM and PM proteins were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, There was evidence of change in the molecular masses of several PM proteins and OM proteins compared to controls. There was evidence of damage to the DNA obtained from irradiated cells. Scanning electron microscopic studies showed that there was coaggregation of P. gingivalis cells when sensitized and then exposed to laser light, These results suggest that lethal photosensitization of P, gingivalis may involve changes in OM and/or PM proteins and DNA damage mediated by singlet oxygen.

Type: Article
Title: A study of the uptake of toluidine blue O by Porphyromonas gingivalis and the mechanism of lethal photosensitization
Keywords: PHOTODYNAMIC TREATMENT, IN-VITRO, BACTERIA, PROTEINASE, CELLS, YEAST
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci > Department of Surgical Biotechnology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: http://discovery.ucl.ac.uk/id/eprint/154616
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