Parts | Days | Selection | Search | Updates | Downloads | Help

SYLM: Symposium Laser in der Medizin

SYLM 1: Laser in der Medizin I

SYLM 1.4: Invited Talk

Tuesday, March 14, 2017, 15:30–16:00, GW1 HS

Photons fight against pathogenic bacteria — •Wolfgang Bäumler — Department of Dermatology, University of Regensburg, Germany

Photodynamic inactivation of bacteria proves to be an innovative, alternative method to kill pathogenic bacteria. In the photodynamic process a photosensitizer molecule absorb light, populates thereby its triplet T1 state via intersystem crossing, and subsequently transfer the energy from T1 state to adjacent oxygen molecules to generate reactive oxygen species (ROS). Among ROS, the so-called singlet oxygen is generated, which is the energetically lowest excited state of molecular oxygen. Singlet oxygen causes oxidative damage of important biomolecules (lipids, proteins) in living cells like bacteria. Such cells are killed in case of sufficiently high number of singlet oxygen molecules. Due to the short lifetime, singlet oxygen should be generated close to bacteria. This is accomplished by cationic photosensitizer molecules which can attach to the negatively charged surface of bacteria. Singlet oxygen production in solution or bacteria can be proven by time- and spectral resolved detection of its luminescence at 1270 nm. To allow broad application, photosensitizers should be safe when applied in humans. Natural substances like vitamin B2 or Phenalenone are known to produce singlet oxygen upon irradiation with high quantum yields of about 75% to 98%. Different bacteria can be effectively killed with PIB with up to 6 log10 steps.