Laser photobiostimulation of wound healing: Defining a dose response for splinted wounds in diabetic mice

Abstract Background and Objectives We have used a 660 nm, 80 mW laser diode in genetic diabetic mice to stimulate the healing of wounds covered with a Tegaderm HP dressing that causes a retardation of contraction (splinted wounds). The purpose of our study was to examine the effects of irradiating the wounds for different time intervals in order to determine a dose response relationship. Materials and Methods A circular excisional wound was made on the left flank of diabetic mice using a 5‐mm skin punch, and covered with a Tegaderm HP dressing. Mice were allocated to four groups in which wounds were irradiated 660 nm, 80 mW for 0, 10, 20, or 40 seconds each day for 7 days. In total, 51 mice were used. Wounds were harvested on day 14 and the healing assessed from hematoxylin–eosin stained sections examined by light microscopy. Results The wounds were splinted in 40 of the mice, and splinting caused a retardation of healing. The findings for the four treatments showed that irradiation for 20 second/day for 7 days brought about the greatest extent of healing. The wounds healed mainly by re‐epithelization and granulation tissue formation. This duration of irradiation represents an energy dose of 1.6 J per irradiation and, for an estimated area of irradiation of 32–43 mm 2 , corresponds to an energy density of 3.7–5.0 J/cm 2 . Conclusion Irradiation with 660 nm, 80 mW at an energy density of 3.7–5.0 J/cm 2 each day for 7 days caused the maximal stimulation of healing in splinted wounds of diabetic mice. Lasers Surg. Med. 42:816–824, 2010 © 2010 Wiley‐Liss, Inc.