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Article

In the Right Light: Photodynamic Inactivation of Microorganisms Using a LED-Based Illumination Device Tailored for the Antimicrobial Application

Laboratory of Photodynamic Inactivation of Microorganisms, Department of Biosciences, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria
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Received: 5 December 2019 / Revised: 23 December 2019 / Accepted: 27 December 2019 / Published: 30 December 2019
(This article belongs to the Special Issue Photodynamic Therapy in the Inactivation of Microorganisms)
Drug-resistant bacteria threaten the health of people world-wide and cause high costs to their health systems. According to Scientific American, the number of regrettable fatalities due to the bacteria that are resistant to conventional antibiotics will sum up to 300 million until 2050 if the problem is not tackled immediately. Photodynamic Inactivation (PDI) has proven effective against microorganisms irrespective of their resistance to conventional treatment, but for the translation into clinical practice, economic, homogenous and powerful light sources holding approval as medical devices are needed. In this study we present two novel light emitting diode (LED)-based lamps (Repuls7PDI-red and Repuls7PDI-blue) tailored for application in PDI and demonstrate their photodynamic efficiency upon using either methylene blue (MB), a photoactive compound widely used in PDI, or Sodium Magnesium Chlorophyllin (CHL), a water-soluble derivative of chlorophyll, which holds approval as food additive E140, against bacteria and fungi. Gram+ Staphylococcus aureus, Gram− Escherichia coli and the yeast Candida albicans serve as model systems. Repuls7PDI-red emits a wavelength of 635 nm and an intensity of 27.6 ± 2.4 mW·cm−2 at a distance of 13.5 cm between the light source and the target, while the Repuls7PDI-blue allows an exposure at 433 nm (within the range of violet light) (6.4 ± 0.5 mW·cm−2 at 13.5 cm). Methylene blue was photoactivated with the Repuls7PDI-red at 635 nm (25.6 J·cm−2) and allows for photokilling of E. coli by more than 6 log10 steps at a concentration of 10 µM MB. Using equal parameters, more than 99.99999% of S. aureus (20 µM MB) and 99.99% of C. albicans (50 µM MB) were killed. If blue light (Repuls7PDI-blue, 433 nm, 6.6 J·cm2) is used to trigger the production of reactive oxygen species (ROS), a photoinactivation of S. aureus (5 µM CHL, CFU reduction > 7 log10) and C. albicans (>7 log10) below the detection limit is achieved. PDI based on CHL (10 µM) using red light activation reduces the number of viable S. aureus by more than 6 log10. Our data prove that both LED-based light sources are applicable for Photodynamic Inactivation. Their easy-to-use concept, high light output and well-defined wavelength might facilitate the translation of PDI into clinical practice. View Full-Text
Keywords: Photodynamic Inactivation; photosensitizers; natural substances; light source; light emitting diode Photodynamic Inactivation; photosensitizers; natural substances; light source; light emitting diode
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MDPI and ACS Style

Hasenleitner, M.; Plaetzer, K. In the Right Light: Photodynamic Inactivation of Microorganisms Using a LED-Based Illumination Device Tailored for the Antimicrobial Application. Antibiotics 2020, 9, 13. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9010013

AMA Style

Hasenleitner M, Plaetzer K. In the Right Light: Photodynamic Inactivation of Microorganisms Using a LED-Based Illumination Device Tailored for the Antimicrobial Application. Antibiotics. 2020; 9(1):13. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9010013

Chicago/Turabian Style

Hasenleitner, Martina, and Kristjan Plaetzer. 2020. "In the Right Light: Photodynamic Inactivation of Microorganisms Using a LED-Based Illumination Device Tailored for the Antimicrobial Application" Antibiotics 9, no. 1: 13. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9010013

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