14 March 2014 In vitro studies of chlorin e6-assisted photodynamic inactivation of Helicobacter pylori
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Helicobacter pylori (HP), a gram-negative microaerophilic bacterium located in gastric mucosa, plays an im- portant role in gastro carcinogenesis. Due to the increasing emergence of antibiotic resistance, photodynamic inactivation of bacteria presents a new approach to treat bacterial infections, like HP. In vitro experiments were performed to determine the irradiation conditions for a complete inactivation of HP with the photosensitizer Chlorin e6 (Ce6). The HP strain CCUG 38770 (Culture Collection, University of Gothenburg, Sweden) was routinely cultured under microaerophilic conditions, suspended in sodium chloride, incubated with Ce6 and irradiated briefly with red light of the appropriate wavelength of λ = 660 nm. Series of measurements of different Ce6-concentrations (0.1 μM - 100 μM) were carried out, whereby the incubation time was kept constant at 1 min. The absorbed energy dose has been selected in varying the irradiation time (1 s - 300 s) and the power density (4.5 mW/cm2 - 31 mW/cm2 ). Quantification of inactivation was performed by enumeration of the grown colonies. In addition, the accumulation of Ce6 in HP cells was studied more precisely by uorescence spectroscopy. With a Ce6 concentration of 100 μM and a power density of 9 mW cm2 , a 6-log10 reduction in the survival rate of HP was achieved within 30 seconds of irradiation. In conclusion the most relevant factor for the inactivation of HP is the exposure time of irradiation, followed by the concentration of Ce6 and the light intensity. Further studies with HP strains obtained from patient specimens are under current investigation.
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C. Simon, C. Simon, C. Mohrbacher, C. Mohrbacher, D. Hüttenberger, D. Hüttenberger, Ina Bauer-Marschall, Ina Bauer-Marschall, C. Krickhahn, C. Krickhahn, A. Stachon, A. Stachon, H.-J. Foth, H.-J. Foth, "In vitro studies of chlorin e6-assisted photodynamic inactivation of Helicobacter pylori", Proc. SPIE 8931, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXIII, 893115 (14 March 2014); doi: 10.1117/12.2037769; https://doi.org/10.1117/12.2037769

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