Antibacterial photodynamic therapy with curcumin and Curcuma xanthorrhiza extract against Streptococcus mutans.

BACKGROUND: Bacteria are becoming increasingly resistant to conventional antibacterial chemotherapy. This has prompted the application of antibacterial photodynamic therapy (aPDT) in bacteria-related diseases due to its excellent biocide effects. However, few studies have attempted to develop a novel photosensitizer based on natural components. The aim of the present study was to compare the aPDT effects of curcumin and Curcuma xanthorrhiza extract (CXE) against Streptococcus mutans.

METHODS: A planktonic suspension containing an S. mutans strain was treated in three separate groups: aPDT with curcumin, CXE, and a mixture of curcumin and CXE (ratio= 1:1) at concentrations of 0, 10, 102 , 103 , and 104 ng/ml. Light irradiation with a center wavelength of 405nm was applied using an LED (power density of 84.5mW for 300s at an energy density of 25.3J/cm2 ). The phototoxicity of photosensitizers against S. mutans was investigated using a colony-forming-unit assay. Percentage logarithmic reductions [log10 (CFU/ml) values] were analyzed using one-way ANOVA followed by the Tukey test (p<0.05) and Student's independent t-test.

RESULTS: The viability of S. mutans in the presence of curcumin, CXE, and a mixture of these two components was substantially reduced during irradiation with 405nm light. The phototoxicity of the photosensitizer varied with its solubility and concentration.

CONCLUSION: These preliminary in vitro findings imply that combining curcumin and CXE with a 405nm LED may be a novel method of applying aPDT. This could be advantageous in preventing and treating dental caries using devices that are readily available in clinics.