Environmental Control of an Argon Plasma Effluent and Its Role in THP-1 Monocyte Function

Plasma medicine is a rapidly advancing field. As one promising application, cold plasma has been ascribed a beneficial role in wound healing in which monocytes/macrophages play an important part. Wound healing and many other physiological and pathological processes are subject to redox control. Cold plasma expels reactive species of many kinds, thereby altering the redox state and mediating cell and tissue responses. Controlling this species efflux could be a valuable asset to control biological effects. We, therefore, investigated the biological response of a plasma treatment regimen that was gas shielded from the ambient environment. In this gas curtain, several N
₂
:O
₂
ratios were investigated, and we discovered a modulation within the composition of active compounds (NO
^-
₂
, NO
^-
₃
, and H
₂
O
₂
) in physiological solutions. Using a human monocyte cell line, the cell's scavenging activity toward these molecules was assessed. With regard to cellular processes important in wound healing, such as cytokines release, O
₂
shielding provided stronger stimulation compared to N
₂
shielding. Altogether, the results support the idea that tuning the plasma-derived reactive species composition may be an interesting approach to improve plasma medical applications.