IADR Abstract Archives
Effects of Synthetic Lawsone Derivatives on Streptococcus Mutans Biofilm Formation
Objectives: To determine antibacterial activity of synthetic lawsone derivatives (LME, 2a, 2b, 2c) against Streptococcus mutans by obtaining the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) and their effects on biofilm formation.
Methods: Bacterial suspension of S.mutans (DMST 41283) was used at the concentration of 105 CFU/ml. The MICs and MBCs were obtained by broth microdilution assay (100-6.25 µg/ml), performed in 96-well microplates, and incubated under anaerobic condition at 37oC for 24 hours. The effects of lawsone derivatives on biofilm formation were determined by crystal violet assay performed in 96-well microplates. S.mutans was inoculated in BHI with 5% (w/v) sucrose containing various concentrations of lawsone derivatives (starting from 1/2 MIC, and 2-fold serially diluted to 1/32 MIC). After incubation at 37°C for 24 h, media and unbound cells were decanted. 0.1% crystal violet was used to stain the biofilm and bound dye was dissolved by 95% alcohol. The quantification of biofilm formation was determined at 6, 12, 20 and 24 hours, by measuring the optical density of the suspension at 600 nm by a microplate reader.
Results: LME, 2a and 2b exhibited equivalent antibacterial activities with the MIC of 1.56 µg/ml. 2c exhibited the weakest activity with the MIC of 6.25 µg/ml. Bactericidal effect of LME was not observed at 100 µg/ml, which was the MBC of 2a and 2b. The inhibitory effects of lawsone derivatives on biofilm formation was time- and concentration-dependent. At the concentration of 1/2 MIC, lawsone derivatives inhibited 89.04-96.59% of 20-hour biofilm formation. For 24-hour biofilm formation, the effects decreased to 50.37-87.39%. None of the agents exhibited such effect at the concentration of ≤ 1/8 MIC.
Conclusions: 2a and 2b are promising anticaries candidates which possess strong antibacterial activities against S.mutans and still exhibit satisfying inhibitory effects on biofilm formation at low concentration.
Methods: Bacterial suspension of S.mutans (DMST 41283) was used at the concentration of 105 CFU/ml. The MICs and MBCs were obtained by broth microdilution assay (100-6.25 µg/ml), performed in 96-well microplates, and incubated under anaerobic condition at 37oC for 24 hours. The effects of lawsone derivatives on biofilm formation were determined by crystal violet assay performed in 96-well microplates. S.mutans was inoculated in BHI with 5% (w/v) sucrose containing various concentrations of lawsone derivatives (starting from 1/2 MIC, and 2-fold serially diluted to 1/32 MIC). After incubation at 37°C for 24 h, media and unbound cells were decanted. 0.1% crystal violet was used to stain the biofilm and bound dye was dissolved by 95% alcohol. The quantification of biofilm formation was determined at 6, 12, 20 and 24 hours, by measuring the optical density of the suspension at 600 nm by a microplate reader.
Results: LME, 2a and 2b exhibited equivalent antibacterial activities with the MIC of 1.56 µg/ml. 2c exhibited the weakest activity with the MIC of 6.25 µg/ml. Bactericidal effect of LME was not observed at 100 µg/ml, which was the MBC of 2a and 2b. The inhibitory effects of lawsone derivatives on biofilm formation was time- and concentration-dependent. At the concentration of 1/2 MIC, lawsone derivatives inhibited 89.04-96.59% of 20-hour biofilm formation. For 24-hour biofilm formation, the effects decreased to 50.37-87.39%. None of the agents exhibited such effect at the concentration of ≤ 1/8 MIC.
Conclusions: 2a and 2b are promising anticaries candidates which possess strong antibacterial activities against S.mutans and still exhibit satisfying inhibitory effects on biofilm formation at low concentration.