Exploring pH Dynamics in Amino Acid Solutions under Low-Temperature Plasma Exposure*

Low temperature plasma (LTP) has emerged as a promising tool across different areas, including cancer therapy, owing to its capacity to selectively target malignant cells without damaging surrounding tissues. A key property of LTP lies in the generation of reactive oxygen and nitrogen species (RONS), which have the ability to modify the pH of the irradiated medium. Upon interaction with water, these species induce an acidic shift in pH; this effect is attributable mainly to the production of acid species like nitrous and nitric acids. The acidification level depends on the plasma source features, such as frequency, voltage, the type of gas used; and the characteristics of the medium, like its buffering capacity.  

Given that low extracellular cancer pH enhances drug resistance and promotes invasive growth, studying how LTP can modify pH is crucial. To develop better cancer treatment strategies, we investigated pH changes induced by LTP in aqueous solutions containing amino acids. We tested voltages from 8 to 10 kV, frequencies from 1 kHz to 4 kHz, and treatment periods up to 2 minutes. Additionally, we analyzed how serine and glycine concentrations, key amino acids in cancer proliferation, influenced the pH of the medium. This study provides insights into how LTP parameters alters pH in solutions and the impact of amino acid concentrations on this process.