Dependence of depth in liquid and gas-flow-rate ratio irradiated with nitric-oxide radicals on proliferation of fibroblast cells

The reaction of NO• with water produces various reactive oxygen and nitrogen species (RONS) with different lifetimes. In this study, we have investigated the dependence of gas-flow-rate ratio and focused on this difference in the lifetime and investigated the promotion of fibroblast proliferation as a function of depth from the air-liquid interface to the cell surface in liquids irradiated with RONS. In the experiment of dependence of gas-flow-rate ratio, the depth in liquid was fixed at 1.0 mm, and Ar gas set to 4.0 slm and N₂ / (N₂ + O₂) was varied from 40, 60, 70, and 80%. In the experiment of dependence of depth in liquid, N₂ / (N₂ + O₂) was fixed at 80%, and the depth in liquid was set to 1.0, 1.3, 1.7, and 2.0 mm. After that, fibroblasts viabilities were measured. The results of the gas-flow-rate ratio dependence showed that the proliferation ratio had a peak at a gas-flow-rate ratio of around 60%. In the dependence of depth in liquid, the maximal promotion was obtained at the shallowest depth of 1.0 mm. These results suggest that NO• or other short-lived RONS generated in liquid is a key factor for proliferation promotion of fibroblast.