Effects of Near-Infrared Low Level Laser Irradiation on Melanoma Cells

Low-level laser (LLL) therapy promotes biostimulating effects in cell cultures growing in nutritional deficit. However, the effects of LLLs on tumor cell lines remain controversial. Studies indicate stimulatory, inhibitory or even no influence in this type of cells. Therefore, the aim of this study was to evaluate the influence of LLL irradiation on the cell viability (with and without nutritional deficit) of human melanoma SKMEL 37 cells and murine melanoma B16F10 cells using an infrared laser (λ = 780 nm) with different radiant exposures. The cell lines were subjected to the LLL 24 h after they were seeded in a 96-well plate at a density of 5 × 104 cells per well. The analysis of cell proliferation by mitochondrial activity occurred at intervals of 24 and 72 h after laser irradiation. At each time, culture medium was removed and 180 µL of PBS and 20 µL of MTT were added. The plates were incubated for 4 h and the absorbance was read in a microplate reader at 570 nm. Results showed a non-significant statistical difference among the groups for both cell lines regardless the nutritional medium. The metabolic pattern was similar among the groups. It is concluded that irradiation with 780 nm laser light at radiant exposures of 30, 90 and 150 J/cm2 and an output power of 40 mW does not promote cell proliferation on melanoma cell lines.