Changes in absorbance of monolayer of living cells induced by laser radiation at 633, 670, and 820 nm

Redox absorbance changes in living cells (monolayer of HeLa cells) under laser irradiation at 633, 670, and 820 nm have been studied by the method of multichannel recording in spectral range 530-890 nm. It has been found that the irradiation causes changes in the absorption spectrum of the cells in two regions, near 754-795 nm (maxima at 757, 775, and 795 nm) and near 812-873 nm (maxima at 819, 837, 858, and 873 nm). Changes occur in band parameters (peak positions, width, and integral intensity). Virtually no changes occur in the red spectral region and a few changes are recorded in the green region near 556-565 nm. The results obtained evidence that cytochrome c oxidase becomes more oxidized (which means that the oxidative metabolism is increased) due to irradiation at all wavelengths used. The results of present experiment support the suggestion (Karu, Lasers Life Sci., 2:53, 1988) that the mechanism of low-power laser therapy at the cellular level is based on the electronic excitation of chromophores in cytochrome c oxidase which modulates α redox status of the molecule and enhances its functional activity