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

Abstract

Antimicrobial blue light (ABL) therapy is one of the novel non-antibiotic approaches and recent studies showed the potential of pulsed ABL. Comparing photoinactivation effect of continuous wave (CW) and pulsed blue light and investigating the impact of varying light parameters. E. coli cells in planktonic were treated with CW and pulsed light (405nm and 450nm) 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. E. coli was more sensitive to 405nm light and the photoinactivation was dose-dependent. Pulsed 405nm 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. Pulsed light has a potential of improving the efficacy of ABL therapy and is worth to be explored deeply further.