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IADR: Effect of Daily Treatment With Blue Light on Biofilm Formation

Posted on June 26, 2014

Cape Town, South Africa – Today, at the 92nd General Session & Exhibition of the International Association for Dental Research (IADR), held in conjunction with the IADR Africa/Middle East Regional Meeting, S. Duarte, New York University, College of Dentistry, N.Y., USA, will present a study titled “Effect of Daily Treatment with Blue Light on Biofilm Formation.” 

Phototherapy with blue light is a promising mechanism of bacterial killing, involving the activation of endogenous photosensitizers in bacteria such as flavins and cytochromes, which lead to production of reactive oxygen species. However the effect of blue light on the biofilm formation has not yet been explored. 

The objective of this study was for the researchers to determine how the daily treatment with blue light affect the formation and composition of a matrix-rich biofilm. Biofilms of Streptococcus mutans UA159 (ATCC 700610) were formed on saliva-coated hydroxyapatite discs for five days. The biofilms were grown in tryptone yeast-extract broth containing 1% (w/v) sucrose and were kept undisturbed for 24 hours to allow initial biofilm formation. The biofilms were then exposed twice daily to non-coherent blue light (LumaCare®; 420 nm). The distance between the light and the sample was 1.0 cm; energy density of 72 J cm-2; and exposure time of 12 minutes and 56 seconds. Positive and negative controls were 0.12% chlorhexidine and 0.89% NaCl, respectively. Biofilms were analyzed for bacterial viability, dry-weight, and extra (EPS-insoluble and soluble) and intracellular (IPS) polysaccharides. Variable pressure scanning electron microscopy and confocal laser scanning microscopy were used to check morphology and viability. 

Daily exposure of biofilm to blue light showed a significant reduction in bacterial viability and dry weight when compared to negative control (p<0.05), and an intermediate effect between the positive and negative controls. The EPS-insoluble reduction when biofilms were exposed to blue light was significantly lower than in both control groups (p<0.05). Blue light treatment also decreased the amount of EPS-soluble and IPS, although it was not statistically different from the negative control (p>0.05). Different morphology and higher proportion of dead cells were also visible when the biofilms were treated with blue light. The researchers found that daily treatment with blue light is a promising mechanism for the reduction of matrix-rich biofilm formation. 

This is a summary of abstract #132, “Effect of Daily Treatment with Blue Light on Biofilm Formation,” to be presented by S. Duarte on Thursday, June 26, 2014, 8 a.m. - 9:30 a.m. in Meeting Room 1.63 of the Cape Town International Convention Centre.