Assessment of radiobiological impacts of threshold doses of alpha particles on A549 human lung cancer cells following direct irradiation exposure

Purpose: Investigation of the radiobiological effects of low-doses of alpha particles on the inhibition of human lung cancer cell growth rate. Materials and methods: To examine whether alpha particles inhibit lung cancer cell growth, human adenocarcinoma A549 cells were irradiated for 10-180 s. The irradiated processes were done during cell culture, using of micro alpha irradiation collimators. The density of accumulated alpha particles is assessed using CR-39NTDs. The MTT cell viability assay was performed on 96-well plates with cell lines seeded at 1 x 10(4) cells/well to test the cytotoxic effect. The media was removed after 72 h to determine the cytotoxic effect. Results: Growth Rate Inhibition (GRI%) has been investigated with different irradiation times tIR ranges (very short: 10-50 s, short: 60-180 s), obtaining the following results: GRI% < 10% for the first range, GRI% increased to over 25% at 60 s, while, for the second range, GRI % increased with a power law relationship. Also, a reduced serum-stimulated growth in the lung cancer cell lines has been observed. Conclusions: This study investigated that the low doses (i.e. low densities) of accumulated alpha particles) in human lung cancer cells have a significant impact on the Growth Rate Inhibition (GRI%), depending on the irradiation time, showing that there it occurs a critical time of 60 s at which significant changes could start to take place.