Melanin and the cellular effects of ultrashort pulse, near infrared laser radiation

Randolph D. Glickman, Neeru Kumar, Benjamin A. Rockwell, Gary D. Noojin, Michael L. Denton, David J. Stolarski

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


Our research into laser bioeffects has increasingly focused on cytotoxic mechanisms affecting genomic expression and programmed cellular stress responses. In the context of DNA damage, we previously reported that more DNA strand breaks were produced in cultured retinal pigment epithelium (RPE) cells exposed to ultrashort pulse, than to CW, near-infrared (NIR) laser radiation. To test the hypothesis that RPE melanin was the cellular chromophore responsible for mediating this damage, the experiments were repeated with a line of human-derived RPE cells that could be grown in culture expressing varying levels of pigmentation. Lightly-pigmented cells were either unexposed, or exposed to the output of a Ti:Sapphire laser producing 810 nm light in mode-locked pulses (48-fsec at 80 MHz), or as CW radiation. Cells were irradiated at 160 W/cm 2 or 80 W/cm 2 (the estimated ED 50 or half-ED 50 for a retinal lesion). Immediately following the laser exposure, cells were processed for the comet assay. Longer "comet" tails and larger "comet" areas indicated more DNA strand breaks. In lightly-pigmented RPE cells, the overall comet assay differences among the laser-exposed groups were smaller than those observed in our earlier experiments which utilized highly pigmented primary cells. The comet tail lengths of cells exposed to the mode-locked pulses at the ED 50, however, were significantly longer than those of the controls or the CW-exposed cells. The other comet assay parameters examined (tail moment, comet area) did not show consistent differences among the groups. While these results support the involvement of melanin in the ultrashort pulse laser-induced damage to DNA, they do not exclude the involvement of other cellular chromophores. Some preliminary experiments describing other measures of cellular stress responses to laser-induced oxidative stress are described.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsS.L. Jacques, D.D. Duncan, S.J. Kirkpatrick, A. Kriete
Number of pages9
StatePublished - 2003
EventPROGRESS IN BIOMEDICAL OPTICS AND IMAGING: Laser-Tissue Interaction XIV - San Jose, CA, United States
Duration: Jan 25 2003Jan 29 2003


Country/TerritoryUnited States
CitySan Jose, CA


  • Comet assay
  • Cytotoxicity
  • Genotoxicity
  • Melanin
  • Oxidative stress
  • RPE cells
  • Stress response
  • Ultrashort pulse

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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