Blue-light effect on periopathogenic multi-Species biofilm in-vitro model

Objectives: Oral bacteria are organized in multi-species biofilm. Using visible light exposure we showed a selective inhibitory effect on the gram-negative anaerobes. The aim of the study is to evaluate the effect of non-coherent blue light treatment on multi-species in-vitro biofilm.
Methods: 24-well plates were coated with saliva, and inoculated with S.sanguis and A.naeslundii in GCF simulating media for 24 hrs in anaerobic conditions. Following initial biofilm formation, P.gingivalis and F.nucleatum were added for additional 48 hrs. Mature biofilm was exposed to blue-light and compared with non-exposed biofilm immediately after exposure and 24 hrs after exposure. The structure of thebiofilm was analyzed by confocal microscopy using live/dead staining and the P.gingivalis and F.nucleatum growth was determined by FACS analysis.
Results: Upon exposure to blue light (1W/cm², 2 min) the periopathogenic bacteria (P. gingivalis and F. nucleatum) viability was reduced by 50%, while the ratio of dead bacteria within the periopathogens were increased from 65% (unexposed) to 85% (exposed) for F. nucleatum and from 20% to 60% for P. gingivalis. Using live/dead florescent staining, it was evident that most bacteria within the biofilm were viable, with little non-vital islands of bacteria. The exposure of blue light led to a clear reduction in viable biofilm area throughout all the depths of the biofilm.
Conclusions: The multi species periodontal biofilm model contains mostly viable bacteria. The exposure to blue -light showed a selective effect on the growth of periopathogens P. gingivalis and F.nucleatum. This phenomenon may lead to a novel approach for “replacement therapy” aiming to establish a non-periopathogenic biofilm.