title: A study of the effects of phototherapy dose interval on photobiomodulation of cell cultures.
abstract: OBJECTIVE
  Dosimetry and treatment frequency are controversial phototherapy issues. Efficacy of dose fractionation on photobiomodulation was evaluated in vitro.
  
  
  METHODS
  Human HEP-2 and murine L-929 cell lines were cultured in complete DMEM media. Photoradiation (670 nm, 5 J/cm2/treatment, 50 J/cm2 total energy delivery), was performed varying treatments per 24 hour period: Group I (Controls)-0, Group II-1/d, Group III-2/d, Group IV-4/d. Cell proliferation was measured using Cyquant (fluorescent DNA content) and MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrasolium bromide) assays for 240 hours post therapy. A proliferation index: PI = (#Cells Experimental(t) / #Cells Control(t)) was computed.
  
  
  RESULTS
  MTT assay results demonstrated maximal response in Group III (P < 0.05, n = 3). Cyquant maxima occurred in HEP-2 Groups II and III (P < 0.045) and L-929 Group III (P < 0.091).
  
  
  CONCLUSIONS
  Cellular response to dose frequency varies. More frequent treatments (2/24 hours) increased metabolism and proliferation in both cell lines. Further investigation of dose fractionation in phototherapy is warranted.
authors.affiliation: Laser Center, Rochester General Hospital, Rochester, New York 14621-3095, 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: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects*; D004396:Coloring Agents / Q000493:pharmacokinetics; D003239:Connective Tissue Cells / Q000502:physiology / Q000528:radiation effects*; D019583:Dose Fractionation, Radiation; D004847:Epithelial Cells / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D051379:Mice; D010789:Phototherapy; D013778:Tetrazolium Salts / Q000493:pharmacokinetics; D013844:Thiazoles / Q000493:pharmacokinetics; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue