Low-power red laser and ultraviolet A LED on <i>Saccharomyces cerevisiae</i> and plasmid DNA

Abstract Therapeutic protocols based on non-ionizing radiation from low-power lasers and light-emitting diodes (LEDs) have been proposed for treatment and prevention of diseases and conditions based on photobiomodulation. Despite therapeutic applications of such radiations their effects on genomic stability are not understood. Thus, the aim of this study was to assess effects of low-power red laser and ultraviolet A LED on Saccharomyces cerevisiae cultures proficient and deficient in DNA repair, and on plasmid DNA. Cultures of S. cerevisiae FF18733 (wild type) and CD138 (deficient in oxidative DNA damage repair), in the exponential growth phase, were irradiated with low-power red laser (660 nm; 5.3, 10.6 and 21.2 J cm −2 ) and ultraviolet A LED (390 nm; 1.5, 3.0 and 6.0 J cm −2 ) alone and simultaneously, and the cell viability was evaluated. The cell proliferation was evaluated through colony counting at 0, 3, 6, 9, 24, 27, 30 and 33 h after irradiation. Also, pUC19 plasmid samples were irradiated, submitted to agarose gel electrophoresis and percentage of plasmid forms were evaluated. Results showed neither significant difference between treatments and control survival fractions, nor significant changes in electrophoretic profile of plasmids. The results indicate that the irradiation with low-power red laser and ultraviolet A LED, alone and simultaneously, at the fluences evaluated, does not alter cell viability in S. cerevisiae cultures proficient and deficient in repair of oxidative damages, and does not induce single and double DNA strand breaks in plasmid DNA.