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Power density and exposure time of He‐Ne laser irradiation are more important than total energy dose in photo‐biomodulation of human fibroblasts in vitro
Author(s) -
van Breugel Hans H. F. I.,
Bär P. R. Dop
Publication year - 1992
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.1900120512
Subject(s) - irradiation , in vitro , laser , energy density , biophysics , power density , materials science , chemistry , biomedical engineering , optics , radiochemistry , power (physics) , medicine , biology , biochemistry , physics , engineering physics , quantum mechanics , nuclear physics
The absorption spectrum of human fibroblast monolayers showed several absorption peaks, among them one at a wavelength of 630 nm. Cultures of these fibroblasts were subjected to He‐Ne laser (632.8 nm) irradiation of various energy doses by varying power density and exposure time. On three consecutive days the cell monolayers were irradiated for periods between 0.5 and 10 min. Laser power varied from 0.55 to 5.98 mW. Both cell number and collagen type I production were determined for each irradiation condition within one experiment. Results show that laser power below 2.91 mW could enhance cell proliferation (as determined by cell counting), whereas higher laser power (5.98 mW) had no effect. Stimulatory effects were most pronounced at irradiation times between 0.5 and 2 min. Collagen type I production (as determined by an ELISA) was affected in the opposite direction to cell proliferation: when the cell proliferation was increased, collagen type I production was decreased. From these experiments it is clear that exposure time and power density determine the effects of laser irradiation. Both stimulation and inhibition of the observed cell properties can be obtained with the same laser on the same cells. © 1992 Wiley‐Liss, Inc.