Annular Shape RF Jet in Contact with Aerosol: UV Emission Control for Safe Biomedical Application

In the last decades, atmospheric pressure plasma jets (APPJs) have shown a lot of potential as an alternative to conventional methods in autoimmune disease treatments and wound healing[1]. Their advantage is assigned to the simultaneous generation of ions, metastables, radiation, reactive oxygennitrogen species, [2]. Among others, AAPJs operating in Ar are considered of high commercial potential in medicine due to relatively low operational costs. Nevertheless, UV radiation from argon excimers Ar
2
* is always present in such sources, limiting its possible utilization and rising concerns on device safety. For this reason, a detailed study on UV/VUV radiation generation in argon plasmas and its biological effect is important for the optimization of the treatment and end user applications. Accordingly, we developed radio-frequency RF APPJ, designed in annular geometry that allows aerosol introduction in the plasma effluent. In this work, the production of UV/VUV radiation in the plasma region and its contribution to the total plasma biological effect during fibroblast cells and plasmid DNA treatment have been studied. The study of UV biological effect was performed by a combination of VUV spectroscopy with fluorescence imaging of the treatment patterns on artificial skin, and finally in-vitro tests. Special attention has been given to the effect of aerosol presence on UV transport to the treated sample. It was revealed that UV radiation is dominated at deep UV below 200 nm by Ar
2
*, OI followed by lower intensity bands located at the region above 250 nm and attributed to NO and N
2
excited states emission. It has been shown that Ar
2
* and OI originate from the active plasma, while NO and N
2
emission is due to air intrusion. Presence of the aerosol has strong effect on UV absorption, reducing the UV radiation effect on cells viability and plasmid DNA defragmentation. The use of RF plasma in combination with an aerosol is proposed as a tool to control the plasma side effects attributed to presence of VUV/UV radiation.