AN INVESTIGATION OF THE CYTOTOXIC AND MUTAGENIC POTENTIAL OF LOW-INTENSITY LASER IRRADIATION IN FRIEND-ERYTHROLEUKEMIA CELLS

The purpose of this study was to investigate the cytotoxic and genotox ic potential of low intensity laser irradiation (660 nm, 12 mW, 5 kHz) on mammalian cells. Thymidine kinase (TK)-positive and TK-deficient F riend erythroleukaemia (FEL) cells, clone 707 and subclone 707BUF resp ectively, were used in this investigation. Following irradiation of ex ponentially growing cells in suspension at doses of 2 and 20 J/cm(2) a number of sensitive bioassays were used to facilitate the detection o f laser-induced mutations, DNA damage and cell killing. Mutations were assessed by the examination of chromosome spreads, the determination of micronucleus frequency and by the determination of the mutant frequ ency at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) loc us. DNA damage was quantified using a sensitive ELISA. The cytotoxic e ffect of laser irradiation was assessed using a cloning assay. The res ults of this investigation did not show any significant increase in mu tation frequency, DNA damage or cell survival in the laser-irradiated cells, compared to sham-irradiated controls. The lack of any demonstra ble cytotoxic and genotoxic effects of low intensity laser irradiation on mammalian cells in culture would support it as being a safe modali ty for clinical use.