Aqueous Reactive Species Induced by Dielectric Barrier Discharge Plasma in PBS: A Quantitative Study

This study quantitatively investigated the generation dynamics of reactive oxygen and nitrogen species (RONS) in low-temperature plasma-activated phosphatebuffered saline (PBS) using a dielectric barrier discharge (DBD) system under varied gas atmospheres (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}$</tex>, air, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{O}_{2}$</tex>). Through systematic modulation of plasma discharge power (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5-15 ~\mathrm{W}$</tex>) and treatment duration (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0-60 ~\mathrm{s}$</tex>), coupled with spectrophotometric and fluorometric assays, we characterized the concentration profiles of nitrate (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{NO}_{3}{ }^{-}$</tex>), nitrite (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{NO}_{2}{ }^{-}$</tex>), and hydrogen peroxide (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2} \mathrm{O}_{2}$</tex>), while monitoring pH stability. Key findings reveal: (1) PBS exhibits exceptional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{p H}$</tex> buffering capacity with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt;\mathbf{0. 4} \mathbf{~ p H}$</tex> unit decline during plasma exposure, maintaining a stable neutral microenvironment (7.2-7.6) suitable for cellular studies; (2) Nitrogen-dominated atmospheres (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\approx \mathbf{8 0 \%} \mathbf{N}_{\mathbf{2}}$</tex> content) significantly enhance reactive nitrogen species production (e.g., <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.8 \text{mM} \text{NO}_{3}^{-}$</tex>vs. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12 \mu \mathrm{M} \mathrm{H}_{2} \mathrm{O}_{2}$</tex> after 60-s treatment), attributed to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}$</tex> dissociation-driven nitration pathways and rapid <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2} \mathrm{O}_{2}$</tex> consumption through peroxynitrite synthesis <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(\mathrm{H}_{2} \mathrm{O}_{2}+\text{HNO}_{2} \rightarrow\right. \text{ONOO}^{-}$</tex>) or radical/UV-induced decomposition; (3) Plasmaactivated PBS with enriched <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{NO}_{3}{ }^{-} / \text{NO}_{2}{ }^{-}$</tex>demonstrates potential biomedical applications in promoting osteoblast proliferation (23 % increase vs. control) and angiogenesis. These results highlight the critical role of gas-phase chemistry in tailoring RONS composition, while emphasizing the need for further mechanistic studies on short-lived RONS (e.g., <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\cdot \text{OH}, \text{ONOO}^{-}$</tex>) generation and their spatiotemporal biological effects.