Ruby laser irradiation (694 nm) of human skin biopsies: Assessment by electron spin resonance spectroscopy of free radical production and oxidative stress during laser depilation

Human skin biopsies (hair-bearing scalp skin and non-hair-bearing breast sk in) were treated with t-butylhydroperoxide, irradiated with UV light (UVR) or irradiated with 694 nm ruby laser red light, Free-radical production and oxidative stress were assessed with electron spin resonance spectroscopy ( ESR) using the ascorbate radical as a marker. In comparison with both UVR a nd t-butyl-hydroperoxide (which readily induce the ascorbate radical in hai r-bearing and hairless skin), 694 nm red light does not result in the forma tion of the ascorbate radical in detectable concentrations. Spin-trapping e xperiments with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) showe d that while free radicals could be detected after treatment of skin with t -butylhydroperoxide, radicals could not be trapped after laser treatment. T reatment of lasered skin (containing DMPO) with t-butylhydroperoxide produc ed radical adducts: as wed as the ascorbate radical, demonstrating that the laser neither depletes endogenous ascorbate nor the preadministered spin t rap.. It is concluded that 694 nm red light does not induce oxidative stres s in human skin in levels comparable either to t-butyl hydroperoxide or UV light.