Photodynamic Action of LED-Activated Curcumin againstStaphylococcus aureusInvolving Intracellular ROS Increase and Membrane Damage
Aim. To investigate the effect of photodynamic action of LED-activated curcumin on cell viability, membrane permeability, and intracellular reactive oxygen species ofStaphylococcus aureus.Methods.Staphylococcus aureuswas incubated with the different concentrations of curcumin for 60 min and then irradiated by blue light with the wavelength of 470 nm and with light dose of 3 J/cm2. The colony forming unit assay was used to investigate photocytotoxicity of curcumin onStaphylococcus aureus, confocal laser scanning microscopy (CLSM) and flow cytometry (FCM) for assaying membrane permeability, FCM analysis with DCFH-DA staining for measuring the intracellular ROS level, and transmission electron microscopy (TEM) for observing morphology and structure.Results. Blue light-activated curcumin significantly killedStaphylococcus aureusin a curcumin dose-dependent manner. TEM observed remarkable structural damages inS. aureusafter light-activated curcumin. More red fluorescence of PI dye was found inS. aureustreated by blue light-activated curcumin than in those of the controlled bacterial cells. Intracellular ROS increase was observed after light-activated curcumin.Conclusion. Blue light-activated curcumin markedly damaged membrane permeability, resulting in cell death ofStaphylococcus aureusand highlighted that intracellular ROS increase might be an important event in photodynamic killing ofStaphylococcus aureusin the presence of curcumin.