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An In Vitro Model to Study the Effect of 5-Aminolevulinic Acid-mediated Photodynamic Therapy on Staphylococcus aureus Biofilm
Published on: April 16, 2018
A novel technique of antimicrobial photodynamic therapy - aPDT using 1,9-dimethyl-methylene blue zinc chloride double
Darcy de A Santos1, Pedro Jorge L Crugeira2, Iago P F Nunes3
1Center of Health Science, Federal University of the Reconcavo Bahiano, Carlos Amaral Ave, 1015 - Cajueiro, Santo Antônio de Jesus, BA CEP: 44.574-490, Brazil; Center of Biophotonics, Federal University of Bahia, 62, Araujo Pinho Ave, Canela, Salvador, BA 40110-150, Brazil.
Abstract:
Antimicrobial Photodynamic Therapy (aPDT) is an alternative to conventional treatments of local infections such as the use of antibiotics, which may lead to the development of resistance. aPDT besides requiring the use of a photosensitiser also needs a light source do be carried out. In the search for efficient and low-cost procedure the use of multispectral polarized light (λ400-2000 nm) emerges as a possibility for the execution of aPDT. The use of a highly effective photosensitizer is also of great importance. 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt - DMMB is a potent phenothiazine derivative that presents high photodynamic action due to its high lipophilicity as well as a greater quantum yield of Singlet oxygen and phototoxicity when compared to other Photosensitizers. The aim of this study was to assess, In Vitro, the efficacy of aPDT on Staphylococcus aureus (ATCC 25923) using different concentrations of DMMB associated to a Polarized light source (Bioptron®, 40 mW, ᴓ = 15.8 cm2) using different energy densities. Based on the IC50, 150 and 300 ng/mL of DMMB concentrations were chosen for this study. Twelve experimental groups were used: (Control, PLs, PSs and aPDTs). Serial dilutions (up to 10-8) of the bacterial inoculum were used and the DMMB was added using the two previously determined concentrations. After 5 min of preincubation the dilutions of the inoculum were illuminated by the polarized light source. Subsequently, 100 μL of each dilution, in triplicate, were inoculated into Petri dishes containing TSA medium and incubated in a bacteriological oven at 37 °C for 24-h and quantification of UFCs was done. The results showed significant exponential reduction (p < .0001) of 99.93% (150 ng/mL + LP 10 J/cm2) and 99.97% (300 ng/mL + LP 5 J/cm2) the CFU counts in comparison to non-illuminated control. The results of this study allow to conclude that aPDT carried out with 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt-DMMB and a PL souce was efficacious on the reduction (99.97%), in vitro, of the bacterial counts of S. aureus.
Insights
Antimicrobial photodynamic therapy (aPDT) using 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt (DMMB) and polarized light effectively reduced Staphylococcus aureus in vitro. This study demonstrates aPDT
Area of Science:
- Biochemistry
- Photochemistry
- Microbiology
Background:
- Antimicrobial resistance necessitates alternative infection treatments.
- Antimicrobial Photodynamic Therapy (aPDT) offers a promising alternative to antibiotics.
- 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt (DMMB) is a potent photosensitizer for aPDT.
Purpose of the Study:
- To evaluate the in vitro efficacy of aPDT against Staphylococcus aureus.
- To assess the effectiveness of DMMB combined with polarized light for aPDT.
Main Methods:
- In vitro assessment of aPDT against Staphylococcus aureus (ATCC 25923).
- Utilized varying concentrations of DMMB (150 and 300 ng/mL) with polarized light.
- Quantified colony-forming units (CFUs) after incubation to determine bacterial reduction.
Main Results:
- Significant exponential reduction in Staphylococcus aureus CFUs observed.
- Achieved 99.93% reduction with 150 ng/mL DMMB and 10 J/cm² polarized light.
- Achieved 99.97% reduction with 300 ng/mL DMMB and 5 J/cm² polarized light.
Conclusions:
- aPDT using DMMB and polarized light is highly efficacious against Staphylococcus aureus in vitro.
- The study confirms the potential of DMMB-based aPDT as an alternative antimicrobial strategy.
