The wound healing effects of linearly polarized irradiation in photobiomodulation

We report the fabrication of a polarization-based photobiomodulation (PBM) system and its performance on wound healing effects. The light source for PBM was a 625 nm LED and two different linear polarizations (P-wave and S-wave) were generated using the wire grid linear polarizers. To confirm the effect of PBM on polarization, wounds were created on hairless mice, and the healing process was compared. The light source conditions for comparison were control, two linearly polarized light, and unpolarized light. The light irradiation conditions for each group were based on the energy settings (energy 18 J/cm², power density 30 mW/cm², exposure time 600 sec) commonly used in LED masks. After creating the wound, the light was irradiated only once. To confirm the wound healing effect over time, it was evaluated through wound surface area measurements, self-made optical coherence tomography images, and histological images. In the group irradiated with S-wave polarized light, the percentage from the initial wound size was reduced to 70.73%, and the epithelial tongue ratio reached 58.36% on day 7 after PBM, indicating the fastest recovery. In this way, the potential of a new product that can increase the effect of wound healing or skin regeneration by adjusting the polarization state without irradiating high energy was confirmed.