Effects of red laser, infrared, photodynamic therapy, and green LED on the healing process of third-degree burns: clinical and histological study in rats

The aim of this study was to evaluate the effects of red laser, infrared, photodynamic therapy, and green light-emitting diode (LED) on the healing process of skin burns through clinical and histopathologic analysis in rats. For this, 100 animals were randomly divided into five groups: G1—untreated control (CTR), G2—red laser (LVER), G3—infrared (LINF), G4—photodynamic therapy (PDT), and G5—green LED. Burn was induced on the dorsum of the rat and the treatment of the experimental groups was red light (10 J/cm2, 10 s, 40 mW, and λ660 nm), infrared (10 J/cm2, 10 s, 40 mW, and λ780 nm), green LED irradiation (60 J/cm2, 10 s, λ520, and 550 nm), and photodynamic therapy (10 J/cm2, 40 mW, and λ660 nm), the latter combined with methylene blue photosensitizer at concentration 0.5 μg/mL. Applications were performed daily until day prior to sacrifice of the animal at 3, 7, 14, and 21 days with intraperitoneal anesthetic overdose. The specimens collected were clinically examined and soon after processed and stained with hematoxylin-eosin and Picrosirius for analysis under light and polarized light microscopy, respectively. Animals treated with LVER, LINF, PDT (p < 0.001), and LED (p < 0.05) stimulated production and maturation of collagen, and increased the consumption of food and water compared to the CTR (p < 0.001). Laser λ660 nm and λ780 nm showed the largest wound reductions in all groups (p = 0.001). In conclusion, red laser, infrared, photodynamic therapy, and green LED favored the healing process of third-degree burns in rats.