Investigation of the Physicochemical Properties and Selective Anti-Cancer Efficacy of in-Plasma Treated PBS Using an Exclusive Liquid-Submerged Plasma Jet

Abstract

Cancer remains a leading cause of mortality, emphasizing the need for innovative therapies. Plasma-treated liquids, containing reactive oxygen and nitrogen species, have demonstrated therapeutic potential. This study investigates the physicochemical properties and anti-cancer efficacy of phosphate-buffered saline (PBS) treated using a novel liquid-submerged plasma jet, which enhances interactions between plasma species and the liquid for a more uniform treatment. Operational parameters including voltage, gas flow, and treatment time, were optimized concurrently. Notably, the submerged configuration produced significantly higher H₂O₂ concentrations in PBS (up to 2000 µM) compared to the above-liquid plasma setups reported in literature. However, NO₂⁻ concentrations remained low (6-18 µM). Voltage variations influenced H₂O₂ production but had a minimal effect on NO₂⁻, while gas flow rates did not impact their concentrations. PBS maintained a stable pH, demonstrating its effective buffering capacity. Stability tests showed H₂O₂ remained stable at 21°C, slightly increased at 4°C, and decreased at 37°C; nitrites were stable below 21°C but slightly decreased at 37°C. Plasma-treated PBS selectively reduced oral squamous cell carcinoma (OSCC) cell viability while sparing healthy keratinocytes (HaCaT), with H₂O₂ identified as the primary anti-cancer agent. These findings suggest that PBS plasma-treated using a new liquid-submerged setup shows potential as selective OSCC therapy. Index Terms-hydrogen peroxide, liquid-submerged plasma jet, nitrite, oral squamous cell carcinoma, plasma-treated PBS.