title: Fast and effective photodynamic inactivation of multiresistant bacteria by cationic riboflavin derivatives.
abstract: Photodynamic inactivation of bacteria (PIB) proves to be an additional method to kill pathogenic bacteria. PIB requires photosensitizer molecules that effectively generate reactive oxygen species like singlet oxygen when exposed to visible light. To allow a broad application in medicine, photosensitizers should be safe when applied in humans. Substances like vitamin B2, which are most likely safe, are known to produce singlet oxygen upon irradiation. In the present study, we added positive charges to flavin derivatives to enable attachment of these molecules to the negatively charged surface of bacteria. Two of the synthesized flavin derivatives showed a high quantum yield of singlet oxygen of approximately 75%. Multidrug resistant bacteria like MRSA (Methicillin resistant Staphylococcus aureus), EHEC (enterohemorrhagic Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii were incubated with these flavin derivatives in vitro and were subsequently irradiated with visible light for seconds only. Singlet oxygen production in bacteria was proved by detecting its luminescence at 1270 nm. After irradiation, the number of viable bacteria decreased up to 6 log10 steps depending on the concentration of the flavin derivatives and the light dosimetry. The bactericidal effect of PIB was independent of the bacterial type and the corresponding antibiotic resistance pattern. In contrast, the photosensitizer concentration and light parameters used for bacteria killing did not affect cell viability of human keratinocytes (therapeutic window). Multiresistant bacteria can be safely and effectively killed by a combination of modified vitamin B2 molecules, oxygen and visible light, whereas normal skin cells survive. Further work will include these new photosensitizers for topical application to decolonize bacteria from skin and mucosa.
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Maisch
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Eichner
authors.affiliation: Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Späth
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Anita
authors.initials: A
authors.lastname: Gollmer
authors.affiliation: Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: König
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Regensburger
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bäumler
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects / Q000528:radiation effects; D001424:Bacterial Infections / Q000628:therapy; D002460:Cell Line; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000528:radiation effects; D054324:Enterohemorrhagic Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000382:microbiology; D008027:Light; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000528:radiation effects; D012256:Riboflavin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D026082:Singlet Oxygen / Q000494:pharmacology*
chemical_list: C000600152:FLASH-01a; C000600153:FLASH-07a; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; D012256:Riboflavin