Johannes Regensburger

University Hospital Regensburg

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Tim Maisch

University Hospital Regensburg

Wolfgang Bäumler

University Hospital Regensburg

Anita Gollmer

University Hospital Regensburg

Fabian Cieplik

University of Freiburg

Karl‐Anton Hiller

University Hospital Regensburg

Andreas Späth

Friedrich-Alexander-Universität Erlangen-Nürnberg

Ariane Felgenträger

University Hospital Regensburg

Michael Landthaler

University Hospital Regensburg

Alena Knak

University of Regensburg

Anja Eichner

University Hospital Regensburg

Cooperative Institutions

University of Regensburg

University Hospital Regensburg

University Medical Center

Graz University of Technology

Institute of Organic Chemistry

United States Food and Drug Administration

Czech Academy of Sciences, Institute of Analytical Chemistry

University of Zurich

Leibniz-Institute for Food Systems Biology at the Technical University of Munich

Freie Universität Berlin

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Blue light kills Aggregatibacter actinomycetemcomitans due to its endogenous photosensitizers

Clinical Oral Investigations (2013)

Fabian Cieplik Andreas Späth Christoph Leibl Anita Gollmer Johannes Regensburger

Aggregatibacter actinomycetemcomitans

Periodontal pathogen

10.1007/s00784-013-1151-8

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Citations (100)

Fast and Effective Photodynamic Inactivation of Multiresistant Bacteria by Cationic Riboflavin Derivatives

PLoS ONE (2014)

Tim Maisch Anja Eichner Andreas Späth Anita Gollmer Burkhard König

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.

Acinetobacter baumannii

10.1371/journal.pone.0111792

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Citations (114)

Intrinsic Artefacts in Optical Oxygen Sensors—How Reliable are our Measurements?

Chemistry - A European Journal (2015)

Philipp Lehner Christoph Staudinger Sergey M. Borisov Johannes Regensburger Ingo Klimant

Abstract Optical oxygen sensing is of broad interest in many areas of research, such as medicine, food processing, and micro‐ and marine biology. The operation principle of optical oxygen sensors is well established and these sensors are routinely employed in lab and field experiments. Ultratrace oxygen sensors, which enable measurements in the sub‐nanomolar region (dissolved oxygen), are becoming increasingly important. Such sensors prominently exhibit phenomena that complicate calibration and measurements. However, these phenomena are not constrained to ultratrace sensors; rather, these effects are inherent to the way optical oxygen sensors work and may influence any optical oxygen measurement when certain conditions are met. This scenario is especially true for applications that deal with high‐excitation light intensities, such as microscopy and microfluidic applications. Herein, we present various effects that we could observe in our studies with ultratrace oxygen sensors and discuss the reasons for their appearance, the mechanism by which they influence measurements, and how to best reduce their impact. The phenomena discussed are oxygen photoconsumption in the sensor material; depletion of the dye ground state by high‐excitation photon‐flux values, which can compromise both intensity and ratiometric‐based measurements; triplet–triplet annihilation; and singlet‐oxygen accumulation, which affects measurements at very low oxygen concentrations.

Oxygen sensor

Limiting oxygen concentration

10.1002/chem.201406037

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Citations (21)

Dirty hands: photodynamic killing of human pathogens like EHEC, MRSA and Candida within seconds

Photochemical & Photobiological Sciences (2012)

Anja Eichner Fernanda Pereira Gonzales Ariane Felgenträger Johannes Regensburger Thomas Holzmann

10.1039/c2pp25164g

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Citations (53)

Time dependence of singlet oxygen luminescence provides an indication of oxygen concentration during oxygen consumption

Journal of Biomedical Optics (2007)

Jürgen Baier Tim Maisch Johannes Regensburger Maria Loibl Rudolf Vasold

Singlet oxygen plays a major role in photodynamic inactivation of tumor cells or bacteria. Its efficacy depends critically on the oxygen concentration [O(2)], which can decrease in case oxygen is consumed caused by oxidative reactions. When detecting singlet oxygen directly by its luminescence at 1270 nm, the course of the luminescence signal is critically affected by [O(2)]. Thus, it should be feasible to monitor oxygen consumption during photo-oxidative processes. Singlet oxygen was generated by exciting a photosensitizer (TMPyP) in aqueous solution (H(2)O or D(2)O) of albumin. Chromatography shows that most of the TMPyP molecules are unbound, and therefore singlet oxygen molecules can diffuse in the solution. A sensor device for oxygen concentration revealed a rapid decrease of [O(2)] (oxygen depletion) in the solution during irradiation. The extent of oxygen depletion in aqueous albumin solution depends on the radiant exposure and the solvent. When detecting the luminescence signal of singlet oxygen, the shape of the luminescence signal significantly changed with irradiation time. Thus, local oxygen consumption could be monitored during photodynamic action by evaluating the course of singlet oxygen luminescence.

Limiting oxygen concentration

10.1117/1.2821153

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Citations (30)

Fast and effective inactivation of Bacillus atrophaeus endospores using light-activated derivatives of vitamin B2

Photochemical & Photobiological Sciences (2014)

Anja Eichner Anita Gollmer Andreas Späth Wolfgang Bäumler Johannes Regensburger

Abstract Highly resistant endospores may cause severe problems in medicine as well as in the food and packaging industries. We found that bacterial endospores can be inactivated quickly with reactive oxygen species (ROS) that were generated by a new generation of flavin photosensitizers. Flavins like the natural compound vitamin B2 are already known to produce ROS but they show a poor antimicrobial photodynamic killing efficacy due to the lack of positive charges. Therefore we synthesized new flavin photosensitizers that have one (FLASH-01a) or eight (FLASH-07a) positive charges and can hence attach to the negatively charged surface of endospores. In this study we used standardized Bacillus atrophaeus endospores (ATCC 9372) as a biological surrogate model for a proof-of-concept study of photodynamic inactivation experiments using FLASH-01a and FLASH-07a. After incubation of spores with different flavin concentrations, the flavin derivatives were excited with blue light at a light dose of 70 J cm −2 . The inactivation of spores was investigated either in suspension or after attachment to polyethylene terephthalate (PET) surfaces. Incubation of spores suspended in Millipore water with 4 mM FLASH-01a for 10 seconds and irradiation with blue light for 10 seconds caused a biologically relevant decrease of spore survival of 3.5 log 10 orders. Using FLASH-07a under the same conditions we achieved a decrease of 4.4 log 10 orders. Immobilized spores on PET surfaces were efficiently killed with 7.0 log 10 orders using 8 mM FLASH-07a. The total treatment time (incubation + irradiation) was as short as 20 seconds. The results of this study show evidence that endospores can be fastly and effectively inactivated with new generations of flavin photosensitizers that may be useful for industrial or medical applications in the future.

10.1039/c4pp00285g

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Citations (22)

Photodynamische Inaktivierung von multiresistenten Bakterien (PIB) – ein neuer Ansatz zur Behandlung oberflächlicher Infektionen im 21. Jahrhundert

JDDG Journal der Deutschen Dermatologischen Gesellschaft (2011)

Tim Maisch Steffen Hackbarth Johannes Regensburger Ariane Felgenträger Wolfgang Bäumler

10.1111/j.1610-0387.2010.07577_suppl.x

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Citations (5)

Fast and effective: intense pulse light photodynamic inactivation of bacteria

Journal of Industrial Microbiology & Biotechnology (2012)

Tim Maisch Franz Spannberger Johannes Regensburger Ariane Felgenträger Wolfgang Bäumler

10.1007/s10295-012-1103-3

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Citations (54)

Luminescence spectroscopy of singlet oxygen enables monitoring of oxygen consumption in biological systems consisting of fatty acids

Physical Chemistry Chemical Physics (2013)

Anita Gollmer Johannes Regensburger Tim Maisch Wolfgang Bäumler

The interaction of singlet oxygen (1O2) generated in a photosensitized process with well-known reference photosensitizers Perinaphthenone (PN) and TMPyP is investigated in a model system consisting of fatty acids and the respective exogenous photosensitizer (PS) in solution by direct detection of the luminescence photons of 1O2 at 1270 nm. Such a model system is a first approach to mimic the complex environment of 1O2 in a biological cell which consists mainly of water, proteins, sugars and lipids. Firstly, the important issue of oxygen consumption is evaluated which has to be considered during luminescence detection of 1O2. It is known that the luminescence signal of 1O2 is dependent on the oxygen concentration of the environment. Cellular components such as lipids represent oxygen consumers due to peroxidation of their unsaturated double bonds. Secondly, the experimental conditions for this model system regarding oxygen consumption are optimized to estimate the rates and rate constants of the coupled system. Thirdly, the triplet decay of the PS can provide more precise information about the actual oxygen concentration close to the PS and can be used, therefore, as a more precise method to determine the oxygen concentration in more complex systems such as a biological cell. The aim is to get a better understanding of photosensitized reactions of 1O2 with cellular components to further improve methodologies, in particular at a cellular level using luminescence spectroscopy. In conclusion, luminescence detection might be a helpful tool to monitor precisely and promptly changes in oxygen concentration in a complex environment.

10.1039/c3cp50841b

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Citations (6)

Photodynamic biofilm inactivation by SAPYR—An exclusive singlet oxygen photosensitizer

Free Radical Biology and Medicine (2013)

Fabian Cieplik Andreas Späth Johannes Regensburger Anita Gollmer Laura Tabenski

Prevention and control of biofilm-growing microorganisms are serious problems in public health due to increasing resistances of some pathogens against antimicrobial drugs and the potential of these microorganisms to cause severe infections in patients. Therefore, alternative approaches that are capable of killing pathogens are needed to supplement standard treatment modalities. One alternative is the photodynamic inactivation of bacteria (PIB). The lethal effect of PIB is based on the principle that visible light activates a photosensitizer, leading to the formation of reactive oxygen species, e.g., singlet oxygen, which induces phototoxicity immediately during illumination. SAPYR is a new generation of photosensitizers. Based on a 7-perinaphthenone structure, it shows a singlet oxygen quantum yield ΦΔ of 99% and is water soluble and photostable. Moreover, it contains a positive charge for good adherence to cell walls of pathogens. In this study, the PIB properties of SAPYR were investigated against monospecies and polyspecies biofilms formed in vitro by oral key pathogens. SAPYR showed a dual mechanism of action against biofilms: (I) it disrupts the structure of the biofilm even without illumination; (II) when irradiated, it inactivates bacteria in a polymicrobial biofilm after one single treatment with an efficacy of ≥99.99%. These results encourage further investigation on the potential of PIB using SAPYR for the treatment of localized infectious diseases.

Phototoxicity

10.1016/j.freeradbiomed.2013.07.031

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Citations (111)