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Updated: Mar 8, 2026
LED-Based In Vitro Screening for Assessing Photoactivable Molecules in Bacterial Photodynamic Inactivation
Published on: January 24, 2025
In vitro antimicrobial activity of LED irradiation on Pseudomonas aeruginosa
Morena Petrini1, Paolo Trentini1, Domenico Tripodi2
1Dental Materials and Medical Chemistry Unit, Department of Medical, Oral and Biotechnological Sciences, University of Chieti, Via dei Vestini 31, 66013 Italy.
Abstract:
Pseudomonas aeruginosa is an opportunistic pathogen responsible of many deaths due to nosocomial pneumonia each year. It is particularly resistant to many different classes of antibiotics and disinfectants. For all these reasons, there is the necessity to find novel approaches of treatment. The aim of this study was to evaluate the effect of 880nm light emitting diodes (LED) irradiation on P. aeruginosa, in vitro. Different LED irradiation parameters (time, energy output and the addition of methylene blue and chlorhexidine) have been tested in order to evaluate the effects on this bacterium. After treatment, the colony forming units per milliliter (CFU mL-1) were recorded and the data were submitted to ANOVA and Bonferroni post hoc tests at a level of significance of 5%. A statistical significant reduction of bacterial count has been registered after 5min of LED irradiation. The antibacterial effect was directly proportional to irradiation time and the output energy. The pre-treatment with methylene blue, seems to be not effective against P. aeruginosa, independently from irradiation parameters. On the contrary, the contemporary action of LED and chlorhexidine has shown a great reduction of bacterial count that was statistical significant respect chlorhexidine and LED alone. The effect of LED irradiation was visible also after 24h, when a lower bacterial count characterized all irradiated samples respect controls.
Insights
880nm light emitting diodes (LED) irradiation effectively reduced Pseudomonas aeruginosa bacterial counts. Combining LED with chlorhexidine showed a significant antibacterial effect, offering a novel treatment approach.
Area of Science:
- Microbiology
- Biomedical Engineering
- Photomedicine
Background:
- Pseudomonas aeruginosa is a major cause of hospital-acquired pneumonia, notorious for its antibiotic resistance.
- The need for novel treatment strategies against P. aeruginosa is critical due to widespread resistance.
- Current disinfectants and antibiotics show limited efficacy against this opportunistic pathogen.
Purpose of the Study:
- To investigate the in vitro efficacy of 880nm light emitting diodes (LED) irradiation against Pseudomonas aeruginosa.
- To assess the impact of varying LED irradiation parameters, including time, energy output, and combination with photosensitizers.
- To evaluate the synergistic or additive effects of LED irradiation with methylene blue and chlorhexidine.
Main Methods:
- Bacterial cultures of P. aeruginosa were exposed to 880nm LED irradiation under various conditions.
- Parameters tested included irradiation time, energy output, and the addition of methylene blue or chlorhexidine.
- Bacterial viability was quantified by colony forming units per milliliter (CFU mL-1) and analyzed using ANOVA and Bonferroni tests.
Main Results:
- A statistically significant reduction in P. aeruginosa CFU mL-1 was observed after 5 minutes of LED irradiation.
- The antibacterial effect increased proportionally with irradiation time and energy output.
- Combining LED irradiation with chlorhexidine resulted in a significantly greater bacterial reduction compared to either agent alone.
- Methylene blue did not enhance the antibacterial effect of LED irradiation against P. aeruginosa.
Conclusions:
- 880nm LED irradiation demonstrates significant in vitro antibacterial activity against Pseudomonas aeruginosa.
- The combination of LED irradiation and chlorhexidine offers a potent synergistic approach for bacterial control.
- LED irradiation presents a promising alternative or adjunct therapy for combating P. aeruginosa infections, with sustained effects observed up to 24 hours.
