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Published on: January 24, 2025
Photodynamic therapy in the treatment of microbial infections: basic principles and perspective applications
Giulio Jori1, Clara Fabris, Marina Soncin
1Department of Biology, University of Padova, Via Ugo Bassi 58B, 35121 Padova, Italy. jori@bio.unipd.it
Background And Objectives:
Photodynamic therapy (PDT) appears to be endowed with several favorable features for the treatment of infections originated by microbial pathogens, including a broad spectrum of action, the efficient inactivation of antibiotic-resistant strains, the low mutagenic potential, and the lack of selection of photoresistant microbial cells. Therefore, intensive studies are being pursued in order to define the scope and field of application of this approach.
Results:
Optimal cytocidal activity against a large variety of bacterial, fungal, and protozoan pathogens has been found to be typical of photosensitizers that are positively charged at physiological pH values (e.g., for the presence of quaternarized amino groups or the association with polylysine moieties) and are characterized by a moderate hydrophobicity (n-octanol/water partition coefficient around 10). These photosensitizers in a micromolar concentration can induce a >4-5 log decrease in the microbial population after incubation times as short as 5-10 minutes and irradiation under mild experimental conditions, such as fluence-rates around 50 mW/cm2 and irradiation times shorter than 15 minutes.
Conclusions:
PDT appears to represent an efficacious alternative modality for the treatment of localized microbial infections through the in situ application of the photosensitizer followed by irradiation of the photosensitizer-loaded infected area. Proposed clinical fields of interest of antimicrobial PDT include the treatment of chronic ulcers, infected burns, acne vulgaris, and a variety of oral infections.
Insights
Photodynamic therapy (PDT) offers a broad-spectrum antimicrobial approach, effectively inactivating resistant strains with minimal mutagenic potential. This method shows promise for treating localized infections like chronic ulcers and acne.
Area of Science:
- Photomedicine
- Antimicrobial Therapy
- Biochemistry
Background:
- Photodynamic therapy (PDT) presents a promising antimicrobial strategy due to its broad-spectrum efficacy.
- Key advantages include inactivation of antibiotic-resistant pathogens and low mutagenic potential.
Purpose of the Study:
- To explore the potential of photodynamic therapy (PDT) as a treatment for microbial infections.
- To define the scope and applications of antimicrobial PDT.
Main Methods:
- Investigated photosensitizers with positive charge and moderate hydrophobicity.
- Evaluated antimicrobial activity against bacterial, fungal, and protozoan pathogens.
Main Results:
- Positively charged photosensitizers with moderate hydrophobicity demonstrated optimal cytocidal activity.
- Micromolar concentrations achieved >4-5 log reduction in microbial populations within 5-10 minutes.
- Mild irradiation conditions (50 mW/cm2, <15 minutes) were effective.
Conclusions:
- PDT is an effective alternative for localized microbial infections via in situ photosensitizer application and irradiation.
- Clinical applications include chronic ulcers, infected burns, acne vulgaris, and oral infections.
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