Human skin contains photolabile nitric oxide (NO) derivatives which decompose after UVA irradiation and release vasoactive NO. However, aside from blue light, barely nothing has been reported about the effects of red and NIR wavelengths. We decided to investigate if photobiomodulation, using visible to NIR light, would increase the release of NO in the skin. A custom-built airtight sleeve which envelopes the forearm of a subject was used to measure the NO emanating from the skin under photobiomodulation conditions and quantified by chemiluminescence detection. Distinct differences in measured NO levels were observed between the non-irradiated condition and PBM conditions.
The effect of near infrared light (940 nm) on the conversion of 5-aminolevulinic acid (5-ALA) to PpIX, a compound involved in photodynamic therapy (PDT), was examined. The back skin of three test subjects was irradiated with continuous wavelength and pulsed infrared light at 940 nm. These irradiations took place 50-53, 24-29, and 8-14 hours prior to the application of the 5-ALA. After a three-hour incubation period with 5-ALA, a FluoDerm™device was used to measure the fluorescence of the skin (emitting wavelength: 400-420 nm; measuring excitation wavelength: 610-720 nm), a direct indication of the activity of 5-ALA. 5-ALA must penetrate the skin and then be converted to PpIX before any fluorescence increase can be observed. Results: For two patients (one was disqualified), the continuous wavelength, 50 hour pre-irradiation condition, the FluoDerm readings showed a 19 to 23% increase in fluorescence (p = 0.05) compared to the no-irradiation, 5-ALA only control.
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