Stabilizing the cold plasma-stimulated medium by regulating medium’s composition

TLDR

Cold plasma–stimulated medium (PSM) shows strong anti‑cancer activity but degrades during storage at most temperatures, requiring freezing at –80 °C. The study aims to uncover the cause of PSM degradation, revealing that reactive species react with cysteine and methionine in the medium. The authors demonstrate that storing PSM in PBS or cysteine/methionine‑free DMEM stabilizes H₂O₂ levels and anti‑cancer activity at 8 °C and –25 °C for at least three days, and that adding 3‑nitro‑L‑tyrosine further protects PSM at 8 °C, establishing a basis for future anti‑cancer use.

Abstract

Abstract Over past several years, the cold plasma-stimulated medium (PSM) has shown its remarkable anti-cancer capacity in par with the direct cold plasma irradiation on cancer cells or tumor tissues. Independent of the cold plasma device, PSM has noticeable advantage of being a flexible platform in cancer treatment. Currently, the largest disadvantage of PSM is its degradation during the storage over a wide temperature range. So far, to stabilize PSM, it must be remained frozen at −80 °C. In this study, we first reveal that the degradation of PSM is mainly due to the reaction between the reactive species and specific amino acids; mainly cysteine and methionine in medium. Based on this finding, both H 2 O 2 in PSM and the anti-cancer capacity of PSM can be significantly stabilized during the storage at 8 °C and −25 °C for at least 3 days by using phosphate-buffered saline (PBS) and cysteine/methionine-free Dulbecco’s Modified Eagle Medium (DMEM). In addition, we demonstrate that adding a tyrosine derivative, 3-Nitro-L-tyrosine, into DMEM can mitigate the degradation of PSM at 8 °C during 3 days of storage. This study provides a solid foundation for the future anti-cancer application of PSM.