Wavelength-Dependent Effects of Photobiomodulation for Wound Care in Diabetic Wounds

Photobiomodulation, showing positive effects on wound healing processes, has been per- 13 formed mainly with lasers in the red/infrared spectrum. Light of shorter wavelengths can signifi- 14 cantly influence biological systems. This study aimed to evaluate and compare the therapeutic ef- 15 fects of pulsed LED light of different wavelengths on wound healing in a diabetic (db/db) mouse 16 excision wound model. LED therapy by REPULS was applied at either 470 nm (blue), 540 nm (green) 17 or 635 nm (red) at 40mW/cm2 each. Wound size and wound perfusion was assessed and correlated 18 to wound temperature and light absorption in the tissue. Red and trend-wise green light positively 19 stimulated wound healing while blue light was ineffective. Light absorption was wavelength-de- 20 pendent and was associated with significantly increased wound perfusion as measured by laser 21 Doppler imaging. Shorter wavelengths ranging from green to blue significantly increased wound 22 surface temperature, while red light, which penetrates deeper into tissue, led to a significant in- 23 crease body core temperature. In summary, wound treatment with pulsed red or green light re- 24 sulted in improved wound healing in diabetic mice. Since impeded wound healing in diabetic pa- 25 tients poses an ever-increasing socio-economic problem, LED therapy may be an effective,- easily 26 applied and cost-efficient supportive treatment for diabetic wound therapy.