In vitro studies of different irradiation conditions for Photodynamic inactivation of Helicobacter pylori

•For PDI of Helicobacter pylori (HP) we used the photosensitizer Chlorin e6.•In vitro experiments were performed in bacterial culture of controlled strains of HP.•A 6-log reduction was achieved with short exposure times in the range of seconds.•A significant effect is observable using a Ce6-concentration of 0.1μM (t=300s).•A fluence rate of 0.81J/cm2 is sufficient for a complete inactivation of HP. Helicobacter pylori (HP) infections are considered to be the main cause for chronic gastritis and gastric ulcers, whereby more than half of the world’s population is nowadays infected. The increased use of antibiotics is leading to an enhanced resistance. Photodynamic inactivation of bacteria seems to be a potential alternative for antibiotic therapies. In our study we used the photosensitizer Chlorin e6 (Ce6) in combination with red light-emitting diodes to inactivate HP in vitro. Ce6 uptake is determined by spectroscopy. Furthermore diverse experiments of different concentrations in the range of 0–100μM of the photosensitizer and exposure times up to 300s are carried out in order to find optimal irradiation parameters (wavelength: 660nm, power density: 9mW/cm2, absorbed dose: up to 2.7J/cm2). The data show a significant reduction after already a few seconds of illumination, even with a low Ce6 concentration in the sub-μM-region. At a concentration of 100μM a nearly total inactivation (6-log10-reduction) of HP was achieved within 60s of irradiation.