Acidification and Nitrite/Nitrate Accumulation by Nonthermal Dielectric Barrier Discharge (DBD) Affect Human Dermal Fibroblasfs

摘要

Reactive species generated by dielectric barrier discharge (DBD) may exert many biological effects including cell toxicity. The reactive nitrogen species nitrogen dioxide hydrolyses in water resulting in acidification and increased osmolality by the formation of nitric acid and nitrous acid. Regarding the small media volumes in which cells were maintained in vitro during plasma treatment, here we address the question of whether cell toxicity effects of plasma may also be mediated by changes of pH, osmolality, and nitrite/nitrate concentrations. DBD treatment led to a treatment time-dependent increase of osmolality, acidification, and accumulation of nitrite and nitrate in buffer and cell culture media. In small buffer volumes, DBD treatment rapidly broke down the buffer capacity, and pH fell below the physiological range. The obtained nitrite/nitrate concentrations were considerably higher than those found in blood and tissues. DBD-treated buffer and acidified buffer containing nitrite/nitrate reduced cell viability of human dermal fibroblasts in the same magnitude. The antioxidant sodium ascorbate could not reverse this effect, whereas it protected fibroblasts partially during DBD treatments. Our results indicate that apart from reactive species, DBD-induced chemical and physical changes in the environment of cells may be responsible for many observed biological effects.