Responses of Fibroblasts, Mesenchymal Stem Cells, and Macrophages after Irradiation with Proton and Silver Ion Emission Guns under Atmospheric Pressure

Abstract Various approaches have been developed to regulate cell growth using physiological or physical stimuli. In this study, we focused on ion implantation technology, which has the potential to deliver both types of stimuli. We developed an ion gun capable of releasing protons or silver ions (Ag+) under atmospheric pressure conditions and used it to irradiate mouse fibroblasts (NIH3T3), mouse mesenchymal stem cells (KUSA-A1), and mouse macrophages (RAW264), evaluating their respective responses. Cell viability decreased with increasing doses of ions emitted from the proton gun. Conversely, high doses of ions emitted from the Ag+ gun reduced the metabolic activity of all the cell types, but low doses enhanced that of RAW264 cells. Thus, the effects varied among ion species, even at nearly equivalent doses, indicating distinct cellular responses depending on the ion provided by the guns. Evaluation of osteogenic differentiation after irradiation with a proton gun in KUSA-A1 cells revealed that low doses of ions emitted from the proton gun promoted alkaline phosphatase activity, while high doses inhibited it. This biphasic response suggests that changes in intracellular pH and energy transfer may contribute to the observed response, warranting further investigations.