A study of the effects of phototherapy dose interval on photobiomodulation of cell cultures.
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.
Brondon
Philip
P
Laser Center, Rochester General Hospital, Rochester, New York 14621-3095, USA.
Stadler
Istvan
I
Lanzafame
Raymond J
RJ
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
D004396:Coloring Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue