Photobiomodulation and Wound Healing: Low-Level Laser Therapy at 661nm in a Scratch Assay Keratinocyte Model.

Abstract

This study aims to investigate the effectiveness of low power red light (661nm) in accelerating the wound healing process of an in vitro scratch assay model of keratinocytes. Furthermore, the study aims to clarify the role of light irradiation parameters, optimize them and gain additional insight into the mechanisms of wound closure as a result of photobiomodulation. Wound healing was studied using scratch assay model of NCTC 2544 keratinocytes. Cells were irradiated with a laser at various power densities and times. Images were acquired at 0, 24, 48 and 72h following the laser treatment. Cellular proliferation was studied by MTT. ROS were studied at 0 and 24h by fluorescence microscopy. Image analysis was used to determine the wound closure rates and quantify ROS. The energy range of 0.18-7.2J/cm2 was not phototoxic, increased cell viability and promoted wound healing. Power and irradiation time proved to be more important than energy. The results indicated the existence of two thresholds in both power and irradiation time that need to be overcome to improve wound healing. An increase in ROS production was observed at 0h only in the group with the lowest healing rate. This early response seemed to block proliferation and finally wound healing. Low level laser light at 661nm enhanced both proliferation and migration in keratinocytes, providing evidence that it could possibly stimulate wound healing in vivo. The observed results are dependent on irradiance and irradiation time rather than energy dose in total.