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.