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  • 1
    UID:
    edochu_18452_25631
    Format: 1 Online-Ressource (11 Seiten)
    Content: The presented work addresses the influence of illumination intensity on the amount and locations of singlet oxygen generation in tumor tissue. We used time-resolved optical detection at the typical emission wavelength around 1270 nm and at 1200 nm where there is no singlet oxygen phosphorescence to determine the phosphorescence kinetics. The discussed data comprise in vivo measurements in tumor-laden HET-CAM and mice. The results show that illumination that is too intense is a major issue, affecting many PDT treatments and all singlet oxygen measurements in vivo so far. In such cases, photosensitization and oxygen consumption exceed oxygen supply, limiting singlet oxygen generation to the blood vessels and walls, while photosensitizers in the surrounding tissue will likely not participate. Being a limitation for the treatment, on one hand, on the other, this finding offers a new method for tumor diagnosis when using photosensitizers exploiting the EPR effect. In contrast to high-intensity PDT, some papers reported successful treatment with nanoparticular drugs using much lower illumination intensity. The question of whether, with such illumination, singlet oxygen is indeed generated in areas apart from vessels and walls, is addressed by numerical analysis. In addition, we discuss how to perform measurements at such low intensities.
    Content: Peer Reviewed
    In: Journal of Personalized Medicine, Basel : MDPI, 12,2022,6
    Language: English
    URL: Volltext  (kostenfrei)
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  • 2
    UID:
    kobvindex_IGB000019319
    In: Humic substances : molecular details and applications in land and water conservation / ed. by: Elham A. Ghabbour ... - New York, 2005. - Chapter 7, S. 99-116
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  • 3
    UID:
    edochu_18452_27206
    Format: 1 Online-Ressource (14 Seiten)
    Content: Recently, we reported induced anoxia as a limiting factor for photodynamic tumor therapy (PDT). This effect occurs in vivo if the amount of generated singlet oxygen that undergoes chemical reactions with cellular components exceeds the local oxygen supply. The amount of generated singlet oxygen depends mainly on photosensitizer (PS) accumulation, efficiency, and illumination intensity. With illumination intensities above a certain threshold, singlet oxygen is limited to the blood vessel and the nearest vicinity; lower intensities allow singlet oxygen generation also in tissue which is a few cell layers away from the vessels. While all experiments so far were limited to light intensities above this threshold, we report experimental results for intensities at both sides of the threshold for the first time, giving proof for the described model. Using time-resolved optical detection in NIR, we demonstrate characteristic, illumination intensity-dependent changes in signal kinetics of singlet oxygen and photosensitizer phosphorescence in vivo. The described analysis allows for better optimization and coordination of PDT drugs and treatment, as well as new diagnostic methods based on gated PS phosphorescence, for which we report a first in vivo feasibility test.
    Content: Peer Reviewed
    In: Journal of Personalized Medicine, Basel : MDPI, 13,2023,5
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
    UID:
    kobvindex_IGB0014336
    In: Photochemical and photobiological sciences. - 3(2004)3, S. 273-280
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  • 5
    UID:
    kobvindex_ZLB13280315
    Format: 146 Seiten , graph. Darst. , 21 cm
    Edition: 1
    ISBN: 3898201716
    Note: Zugl.: Berlin, Humboldt-Univ., Diss., 2000
    Language: German
    Keywords: Polypropylenimine ; Sternpolymere ; Trägersubstanz ; Photosensibilisator ; Fotophysik
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  • 6
    UID:
    edochu_18452_28213
    Format: 1 Online-Ressource (10 Seiten)
    ISSN: 0926-9959 , 1468-3083 , 0926-9959 , 1468-3083
    Content: Background The colonization of skin with pathogenic, partially antibiotic-resistant bacteria is frequently a severe problem in dermatological therapies. For instance, skin colonization with Staphylococcus aureus is even a disease-promoting factor in atopic dermatitis. The photodynamic inactivation (PDI) of bacteria could be a new antibacterial procedure. Upon irradiation with visible light, a special photosensitizer exclusively generates singlet oxygen. This reactive oxygen species kills bacteria via oxidation independent of species or strain and their antibiotic resistance profile causing no bacterial resistance on its part. Objective To investigate the antibacterial potential of a photosensitizer, formulated in a new hydrogel, on human skin ex vivo. Methods The photochemical stability of the photosensitizer and its ability to generate singlet oxygen in the hydrogel was studied. Antimicrobial efficacy of this hydrogel was tested step by step, firstly on inanimate surfaces and then on human skin ex vivo against S. aureus and Pseudomonas aeruginosa using standard colony counting. NBTC staining and TUNEL assays were performed on skin biopsies to investigate potential necrosis and apoptosis effects in skin cells possibly caused by PDI. Results None of the hydrogel components affected the photochemical stability and the life time of singlet oxygen. On inanimate surfaces as well as on the human skin, the number of viable bacteria was reduced by up to 4.8 log10 being more effective than most other antibacterial topical agents. Histology and assays showed that PDI against bacteria on the skin surface caused no harmful effects on the underlying skin cells. Conclusion Photodynamic inactivation hydrogel proved to be effective for decolonization of human skin including the potential to act against superficial skin infections. Being a water-based formulation, the hydrogel should be also suitable for the mucosa. The results of the present ex vivo study form a good basis for conducting clinical studies in vivo.
    Content: Peer Reviewed
    In: Oxford [u.a.] : Wiley-Blackwell, 37,8, Seiten 1649-1658, 0926-9959
    In: 1468-3083
    Language: English
    URL: Volltext  (kostenfrei)
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  • 7
    UID:
    edochu_18452_29924
    Format: 1 Online-Ressource (15 Seiten)
    Content: Antimicrobial resistance is an increasing challenge in semen preservation of breeding animals, especially in the porcine species. Bacteria are a natural component of semen, and their growth should be inhibited to protect sperm fertilizing capacity and the female’s health. In pig breeding, where semen is routinely stored at 17°C in the liquid state, alternatives to conventional antibiotics are urgently needed. Photodynamic inactivation (PDI) of bacteria is a well-established tool in medicine and the food industry but this technology has not been widely adopted in semen preservation. The specific challenge in this setting is to selectively inactivate bacteria while maintaining sperm integrity and functionality. The aim of this study was to test the principle of PDI in liquid stored boar semen using the photosensitizer 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H,23H-porphine (TMPyP) and a white light LED-setup. In the first step, photophysical experiments comprising singlet oxygen phosphorescence kinetics of TMPyP and determination of the photosensitizer triplet time revealed a sufficiently high production of reactive singlet oxygen in the Androstar Premium semen extender, whereas seminal plasma acted as strong quencher. In vitro experiments with extended boar semen showed that the established PDI protocol preserves sperm motility, membrane integrity, DNA integrity, and mitochondrial activity while efficiently reducing the bacteria below the detection limit. A proof-of-concept insemination study confirmed the in vivo fertility of semen after photodynamic treatment. In conclusion, using the PDI approach, an innovative tool was established that efficiently controls bacteria growth in extended boar and maintains sperm fertility. This could be a promising contribution to the One Health concept with the potential to reduce antimicrobial resistance in animal husbandry.
    Content: Peer Reviewed
    In: Lausanne : Frontiers Media, 15
    Language: English
    URL: Volltext  (kostenfrei)
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  • 8
    UID:
    almahu_BV025193053
    Format: 146 S. : , graph. Darst.
    Note: Berlin, Humboldt-Univ., Diss., 2000
    Language: German
    Subjects: Chemistry/Pharmacy
    RVK:
    Keywords: Hochschulschrift
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  • 9
    UID:
    almahu_BV025246045
    Format: 146 S. : , Ill., graph. Darst.
    ISBN: 3-89820-171-6
    Note: Zugl.: Berlin, Humboldt-Univ., Diss., 2000
    Language: German
    Subjects: Chemistry/Pharmacy
    RVK:
    Keywords: Hochschulschrift
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  • 10
    UID:
    almahu_BV024981351
    Format: 59 Bl.
    Note: Berlin, Humboldt-Univ., Diplomarb., 1994
    Language: German
    Keywords: Hochschulschrift
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