title: Melanin density affects photobiomodulation outcomes in cell culture.
abstract: OBJECTIVE
  This study investigated the influence of melanin on the outcome of photoradiation at 670 nm in a cell culture model.
  
  
  BACKGROUND
  Melanins are naturally occurring cutaneous pigments. Human skin is classified into six skin types based on melanin content.
  
  
  METHODS
  Gelatin photo filters were fabricated with varying melanin contents. Human HEP-2 and murine L929 cell lines were cultured in complete Dulbecco's Modified Eagle's Medium (DMEM) media. Photoradiation at 670 nm delivering 5.0 J/cm(2) per treatment/24 h (50 J/cm(2) total fluence) was carried out with melanin filters placed between the light source and the wells using a light-emitting diode (LED) device. Five groups based on percent melanin were treated: group 1, no filter; group 2, gelatin alone; group 3, 0.0125%; group 4, 0.025%; and group 5, 0.050%. Cell proliferation was measured using CyQuant and 3-(4,5-dimethylthiazol-2-yl)-2,5-disphenyl tetrasodiumbromide (MTT) assays for 240 h post-photoradiation.
  
  
  RESULTS
  The Proliferation Index (PI) as measured by CyQuant assay was not statistically different amongst the groups in either cell line. MTT assay results demonstrated a significant dose response effect (p < or = 0.05) in both cell lines with activity inversely proportional to melanin concentration. The relative PI values by MTT assay at 144 h for groups 1, 2, 3, and 4, respectively, were 1.44 +/- 0.06, 1.28 +/- 0.05, 1.20 +/- 0.07, and 1.06 +/- 0.04 for the L-929 cells, and 1.61 +/- 0.03, 1.47 +/- 0.06, 1.35 +/- 0.03, and 1.19 +/- 0.06 for the HEP-2 cells (n = 4; p < 0.05).
  
  
  CONCLUSIONS
  These results demonstrate that cutaneous melanin content should be taken into consideration in photobiomodulation paradigms. Further studies to quantify these effects are warranted.
authors.affiliation: Rochester General Hospital Laser Center, Rochester, New York, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Brondon
authors.forename: Istvan
authors.initials: I
authors.lastname: Stadler
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Lanzafame
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D028022:Low-Level Light Therapy; D008543:Melanins / Q000032:analysis*; D012867:Skin / Q000737:chemistry*
chemical_list: D008543:Melanins