Photoinactivation of Escherichia coli by 405 nm and 450 nm light-emitting diodes: Comparison of continuous wave and pulsed light

BACKGROUNDAntimicrobial blue light (ABL) therapy is one of the novel non-antibiotic approaches and recent studies showed the potential of pulsed ABL.PURPOSEComparing photoinactivation effect of continuous wave (CW) and pulsed blue light and investigating the impact of varying light parameters.METHODSE. coli cells in planktonic were treated with CW and pulsed light (405 nm and 450 nm) at 60 mW/cm2, and the samples were taken to assess survival, reactive oxygen species (ROS) level, damage of cell membrane and metabolic activity. Further, a ROS scavenger was used to find the role of ROS played in ABL therapy.RESULTSE. coli was more sensitive to 405 nm light and the photoinactivation was dose-dependent. Pulsed 405 nm light showed the better antimicrobial effect on E. coli and caused increasing damage of cell membrane. It might be attributed to the ROS production in bacteria.CONCLUSIONPulsed light has a potential of improving the efficacy of ABL therapy and is worth to be explored deeply further.