title: Efficacy of Pulsed 405-nm Light-Emitting Diodes for Antimicrobial Photodynamic Inactivation: Effects of Intensity, Frequency, and Duty Cycle.
abstract: OBJECTIVE
  This study investigates possible advantages in pulsed over continuous 405-nm light-emitting diode (LED) light for bacterial inactivation and energy efficiency.
  
  
  BACKGROUND
  Alternative nonantibiotic methods of disinfection and infection control have become of significant interest. Recent studies have demonstrated the application of systems using 405-nm LEDs for continuous disinfection of the clinical environment, and also for potential treatment of contaminated wounds.
  
  
  METHODS
  Liquid suspensions of 103colony-forming units/mL populations of Staphylococcus aureus were subject to pulsed 405-nm light of different frequencies, duty cycles, and intensities and for different lengths of time.
  
  
  RESULTS
  Pulsed exposures with the same average irradiance of 16 mW/cm2and varying duty cycle (25%, 50%, 75%) showed very similar performance compared with continuous exposures, with 95-98% reduction of S. aureus achieved for all duty cycles. The pulsing frequency was varied in intervals from 100 Hz to 10 kHz and appeared to have little effect on antimicrobial efficacy. However, when comparing pulsed with continuous exposure, an improvement in inactivation per unit optical energy was achieved, with results showing an increase of approximately 83% in optical efficiency.
  
  
  CONCLUSIONS
  These results suggest that under pulsed conditions, a lower energy consumption and lower perceived brightness could be achieved, thus potentially providing improved operating conditions for medical/infection control applications without compromising antimicrobial efficacy.
authors.affiliation: 1 Department of Electronic & Electrical Engineering, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Gillespie
authors.affiliation: 1 Department of Electronic & Electrical Engineering, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .|2 Department of Biomedical Engineering, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Michelle
authors.initials: M
authors.lastname: Maclean
authors.affiliation: 3 Department of Electronic & Electrical Engineering, High Voltage Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Given
authors.affiliation: 3 Department of Electronic & Electrical Engineering, High Voltage Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Mark P
authors.initials: MP
authors.lastname: Wilson
authors.affiliation: 3 Department of Electronic & Electrical Engineering, High Voltage Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Martin D
authors.initials: MD
authors.lastname: Judd
authors.affiliation: 1 Department of Electronic & Electrical Engineering, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .|3 Department of Electronic & Electrical Engineering, High Voltage Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Igor V
authors.initials: IV
authors.lastname: Timoshkin
authors.affiliation: 1 Department of Electronic & Electrical Engineering, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .|3 Department of Electronic & Electrical Engineering, High Voltage Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
authors.forename: Scott J
authors.initials: SJ
authors.lastname: MacGregor
mesh_terms: D004203:Disinfection / Q000379:methods*; D008027:Light; D013211:Staphylococcus aureus / Q000528:radiation effects
keywords: 405 nm light; Staphylococcus; antimicrobial; light-emitting diodes; pulsed light