Antimicrobial photodynamic therapy using a plaque disclosing solution on Streptococcus mutans

Area of Science:

• Biomedical Engineering
• Microbiology
• Photochemistry

Background:

• Antimicrobial photodynamic therapy (aPDT) utilizes photosensitizing dyes and light to kill bacteria.
• Streptococcus mutans (S. mutans) is a primary pathogen in dental caries, often found in hard-to-reach areas.
• Mechanical cleaning of pit and fissure grooves can be challenging.

Purpose of the Study:

• To investigate the bactericidal efficacy of aPDT against S. mutans using a plaque-disclosing solution.
• To evaluate the potential of aPDT as a novel method for treating dental caries in difficult-to-access sites.

Main Methods:

• Phloxine B (PB), a plaque-disclosing agent, was used as the photosensitizer.
• UV-vis spectroscopy analyzed PB's absorption spectrum.
• Electron spin resonance measured reactive oxygen species (ROS) generated by blue LED irradiation.
• Colony Forming Unit (CFU) assays assessed S. mutans viability after aPDT.
• Western blotting quantified protein carbonyl (PC) as an oxidative stress marker.

Main Results:

• Blue light irradiation of PB generated singlet oxygen.
• aPDT significantly reduced S. mutans CFU in a manner dependent on blue light intensity.
• aPDT treatment led to increased expression of protein carbonyl (PC) in S. mutans.

Conclusions:

• aPDT, using PB and blue light, effectively generates ROS to kill S. mutans.
• This plaque-disclosing solution-based aPDT offers a potential new strategy for cleaning pit and fissure grooves, targeting caries pathogens.