Maisch Tim, Eichner Anja, Späth Andreas, Gollmer Anita, König Burkhard, Regensburger Johannes, Bäumler Wolfgang
Department of Dermatology, University Hospital Regensburg, Regensburg, Germany.
Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany.
PLoS One. 2014 Dec 3;9(12):e111792. doi: 10.1371/journal.pone.0111792. eCollection 2014.
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.
细菌的光动力灭活（PIB）被证明是一种杀死致病细菌的额外方法。PIB需要光敏剂分子，当暴露于可见光时，这些分子能有效产生活性氧，如单线态氧。为了在医学中广泛应用，光敏剂应用于人体时应是安全的。像维生素B2这类很可能安全的物质，已知在照射时会产生单线态氧。在本研究中，我们给黄素衍生物添加正电荷，以使这些分子能够附着到带负电荷的细菌表面。两种合成的黄素衍生物显示出约75%的高单线态氧量子产率。耐多药细菌，如耐甲氧西林金黄色葡萄球菌（MRSA）、肠出血性大肠杆菌（EHEC）、铜绿假单胞菌和鲍曼不动杆菌，在体外与这些黄素衍生物一起孵育，随后仅用可见光照射数秒。通过检测细菌在1270nm处的发光证明了单线态氧的产生。照射后，根据黄素衍生物的浓度和光剂量测定，活菌数量最多可减少6个对数级。PIB的杀菌效果与细菌类型和相应的抗生素耐药模式无关。相比之下，用于杀死细菌的光敏剂浓度和光照参数并不影响人角质形成细胞的细胞活力（治疗窗口）。耐多药细菌可以通过修饰的维生素B2分子、氧气和可见光的组合安全有效地杀死，而正常皮肤细胞存活。进一步的工作将包括将这些新型光敏剂用于局部应用，以清除皮肤和黏膜上的细菌。
