Comparison of laser and diode sources for acceleration of in vitro wound healing by low-level light therapy

Low-level light therapy has been shown to improve in vitro wound healing. However, well-defined parameters of different light sources for this therapy are lacking. The goal of this study was (1) to determine if the wavelengths tested are effective for in vitro wound healing and (2) to compare a laser and a light-emitting diode (LED) source at similar wavelengths. We show four wavelengths, delivered by either a laser or LED array, improved in vitro wound healing in A549, U2OS, and PtK2 cells. Improved wound healing occurred through increased cell migration demonstrated through scratch wound and transwell assays. Cell proliferation was tested by the (3-(4,5-dimethylthiazol-2-yl)-5-(3-car-boxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay and was found generally not to be involved in the wound healing process. The laser and LED sources were found to be comparable when equal doses of light were applied. The biological response measured was similar in most cases. We conclude that the laser at 652 (5.57  mW/cm2, 10.02  J/cm2) and 806 nm (1.30  mW/cm2, 2.334  J/cm2) (full bandwidth 5 nm), and LED at 637 (5.57  mW/cm2, 10.02  J/cm2) and 901 nm (1.30  mW/cm2, 2.334  J/cm2) (full bandwidth 17 and 69 nm respectively) induce comparable levels of cell migration and wound closure.