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

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 set-ups reported in literature. However, NO2 concentrations remained low (6-18 μM). Voltage variations influenced H.O. 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 H.O. 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 H.O. identified as the primary anti-cancer agent. These findings suggest that PBS plasma-treated using a new liquid-submerged set-up shows potential as selective OSCC therapy.