Efficacy of a single high dose versus multiple low doses of LLLT on wounded skin fibroblasts

Denise H. Hawkins, Heidi Abrahamse

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Background/purpose: In vivo studies have demonstrated that phototherapy accelerates wound healing in the clinical environment; however the exact mechanism is still not completely understood. The main focus of this study was to use in vitro laboratory results to establish an effective treatment regimen that may be practical and applicable to the clinical environment. This in vitro study aimed to compare the cellular responses of wounded fibroblasts following a single exposure of 5 J/cm2 or multiple exposures of low doses (2.5 J/cm2 or 5 J/cm2) on one day of the week to a single application of a higher dose (16 J/cm2) on day 1 and day 4. Methodology: Cellular responses to Helium-Neon (632.8 nm) laser irradiation were evaluated by measuring changes in cell morphology, cell viability, cell proliferation, membrane integrity and DNA damage. Results: Wounded cells exposed to 5 J/cm2 on day 1 and day 4 showed an increase in cell viability, increase in the release of bFGF, increase in cell density, decrease in ALP enzyme activity and decrease in caspase 3/7 activity indicating a stimulatory effect. Wounded cells exposed to three doses of 5 J/cm2 on day 1 showed a decrease in cell viability and cell proliferation and an increase in LDH cytotoxicity and DNA damage indicating an inhibitory effect. Conclusion: Results indicate that cellular responses are influenced by the combination of dose administered, number of exposures and time between exposures. Single doses administered with sufficient time between exposures is more beneficial to restoring cell function than multiple doses within a short period. Although this work confirms previous reports on the cumulative effect of laser irradiation it provides essential information for the initiation of in vivo clinical studies.

Original languageEnglish
Title of host publicationEuropean Conference on Biomedical Optics, ECBO 2007
PublisherOptical Society of America
ISBN (Print)9780819467713
Publication statusPublished - 2007
EventEuropean Conference on Biomedical Optics, ECBO 2007 - Munich, Germany
Duration: 17 Jun 200717 Jun 2007

Publication series

NameOptics InfoBase Conference Papers
ISSN (Electronic)2162-2701


ConferenceEuropean Conference on Biomedical Optics, ECBO 2007


  • Cell survival
  • Fibroblast proliferation
  • Low level laser
  • Phototherapy

ASJC Scopus subject areas

  • Instrumentation
  • Atomic and Molecular Physics, and Optics


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