Tzu-Yun Chung

Photodynamic Modulation of Wound Healing: A Review of Human and Animal Studies

OBJECTIVE The purpose of this study was to review studies of photodynamic therapy (PDT) on wound healing and cells in vitro, to assess the effects of such therapy. BACKGROUND DATA PDT is used to treat tumors. When activated by light of a specific wavelength, the photosensitizer produces reactive oxygen species (ROS) that kill tumor cells. Low levels of ROS may induce cellular proliferation. METHODS Research articles investigating PDT on wound healing and cells in vitro published up to August 2010 were retrieved from library sources, PubMed and Medline databases, reference lists of articles, and searches of relevant journals. RESULTS The studies indicated that use of various photosensitizers combined with laser irradiation led to improved wound outcomes. For most in vitro studies, there was a decrease in cell growth or viability. CONCLUSIONS PDT improved healing outcomes in several animal wound models, but mainly had an inhibitory effect on cells in vitro. These findings strongly support PDT for wound healing.

Laser Photobiomodulation of Wound Healing in Diabetic and Non-Diabetic Mice: Effects in Splinted and Unsplinted Wounds

OBJECTIVE The aim of this investigation was to compare the healing of laser-irradiated and non-irradiated wounds covered by an occlusive dressing in mice. BACKGROUND DATA Many previous studies of the effects of laser irradiation of experimental wounds in mice and rats did not cover the wounds so that healing occurred mainly by contraction. Healing of covered wounds is slower and mimics more closely wound healing in humans. MATERIALS AND METHODS Forty-seven diabetic and twenty non-diabetic mice were used. A single wound (5 mm diameter) was created on the left flank of each animal and covered by Tegaderm HP dressing (Day 1). Wounds were irradiated (660 nm) for 20 s using a lower power (18 mW) or higher power (80 mW) laser starting immediately post-wounding for seven consecutive days (0.36 or 1.6 J/day); untreated wounds served as controls. Animals were euthanized on Day 8, 10, or 14. Wound specimens were cut and stained using haematoxylin and eosin, and picrosirius red, and examined by microscopy. RESULTS Results confirmed that wound healing was impaired in diabetic mice. Analysis of the data demonstrated that Tegaderm HP dressing had retarded contraction (splinted the wounds) in a large proportion of diabetic mice and, to a lesser extent, in non-diabetic mice. Healing of splinted wounds was delayed compared to unsplinted wounds, but laser irradiation (1.6 J/day, 7 days) stimulated healing by re-epithelization and granulation tissue formation. CONCLUSION These are the first findings of laser-mediated stimulation of healing in splinted wounds. Further studies are needed to assess the effects of different constellation sets of laser parameters in this wound model.

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

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.

Laser photostimulation (660 nm) of wound healing in diabetic mice is not brought about by ameliorating diabetes

We have used a 660‐nm 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). It is possible that the stimulation of healing could be due to possible diabetes‐modifying properties of laser light. This has been examined by using the 660 nm laser to irradiate non‐wounded diabetic mice with the same dose and at same location as for wounded diabetic mice.

Laser photobiostimulation of wound healing: reciprocity of irradiance and exposure time on energy density for splinted wounds in diabetic mice.

We have used a 660 nm 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 influence of irradiance (power density) on wound healing has been examined with the same energy dose delivered to the wounds. This energy dose caused maximal stimulation of healing in a previous study.

Influence of Two Different Fluences on Laser Photobiomodulation of Wound Healing in Diabetic and Nondiabetic Mice

Background: Laser irradiation of wounds in mice and rats was shown in previous studies to stimulate healing but in almost all the studies the wounds were not covered.Purpose: To compare the healing of covered wounds in diabetic and nondiabetic mice and the effect of laser irradiation 660 nm at two different fluences (energy densities).Method: A single wound 5‐mm diameter was made on the left flank of forty‐seven diabetic and twenty nondiabetic mice and covered with Tegaderm HP dressing (day 1). Wounds were irradiated 660 nm 20 s using a low power (18 mW) or high power (80 mW) laser starting immediately post‐wounding for 7 consecutive days, with non‐irradiated wounds as controls. Mice were euthanized on day 8, 10 or 14. Wound specimens were cut and stained with haematoxylin and eosin, and examined by light microscopy.Results: Wound healing was impaired in diabetic mice. Tegaderm HP dressing had retarded contraction in a large proportion of diabetic mice (splinted the wounds) and to a lesser extent in nondi...