Abstract
BackgroundThe use of blue light has been proposed as a direct means of affecting local bacterial infections, however the use of blue light without a photosensitizer to prevent the biofilm development has not yet been explored. The aim of this study was to determine how the twice-daily treatment with blue light affects the development and composition of a matrix-rich biofilm.Methodology/Principal FindingsBiofilms of Streptococcus mutans UA159 were formed on saliva-coated hydroxyapatite discs for 5 days. The biofilms were exposed twice-daily to non-coherent blue light (LumaCare; 420 nm) without a photosensitizer. The distance between the light and the sample was 1.0 cm; energy density of 72 J cm-2; and exposure time of 12 min 56 s. Positive and negative controls were twice-daily 0.12% chlorhexidine (CHX) 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 scanning laser microscopy were used to check biofilm morphology and bacterial viability, respectively. When biofilms were exposed to twice-daily blue light, EPS-insoluble was reduced significantly more than in either control group (CHX and 0.89% NaCl). Bacterial viability and dry weight were also reduced relative to the negative control (0.89% NaCl) when the biofilms were treated with twice-daily blue light. Different morphology was also visible when the biofilms were treated with blue light.ConclusionsTwice-daily treatment with blue light without a photosensitizer is a promising mechanism for the inhibition of matrix-rich biofilm development.
Highlights
Twice-daily treatment with blue light without a photosensitizer is a promising mechanism for the inhibition of matrix-rich biofilm development
Streptococcus mutans is known as the major etiological agent in dental caries [1] and it has a great influence on the development and composition of pathogenic biofilms mainly due to its ability to synthesize extracellular polysaccharides (EPS) [2]
Its antimicrobial mechanism is similar to photodynamic antimicrobial chemotherapy (PACT), the bacterial killing seems to involve the activation of endogenous PS in bacteria, such as flavins and cytochromes, that may lead to production of reactive oxygen species (ROS) [10]
Summary
Streptococcus mutans is known as the major etiological agent in dental caries [1] and it has a great influence on the development and composition of pathogenic biofilms mainly due to its ability to synthesize extracellular polysaccharides (EPS) [2]. The photodynamic antimicrobial chemotherapy (PACT) has been indicated as an alternative to conventional antimicrobial therapy to kill oral bacteria [5,7,8]. It is based on the use of extrinsic photosensitizers (PS), light-absorbing molecules that initiate a photochemical reaction when exposed to light of a specific wavelength. This photochemistry process leads to reactive oxygen species (ROS) formation, which may cause irreversible damage to essential bacterial cell compounds and change cell metabolism resulting in bacterial death [9]. The aim of this study was to determine how the twice-daily treatment with blue light affects the development and composition of a matrix-rich biofilm.
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