Dose-dependent tissue-level characterization of a medical atmospheric pressure argon plasma jet

Nonthermal treatment with cold atmospheric plasma (CAP) is a promising option for local treatment of chronic-inflammatory and precancerous lesions as well as various mucosal cancer diseases, besides its primary indication for wound healing and antiseptics. Atmospheric pressure plasma jets (APPJs) are versatile plasma sources, some of which are well-characterized and medically approved. The characterization of APPJs, however, is often based on the treatment of simple solutions or even studies on the plasma effluent itself. To better assess the in vivo effects of CAP treatment, this study aims to recapitulate and study the physicochemical tissue-level effects of APPJ treatment on human primary mucosal tissue and tissue models. High resolution on-tissue infrared (IR) thermography and a first-time-performed spatially resolved optical emission spectroscopy (OES) of the APPJ emissions did not identify potentially tissue-harming effects. In this study, electron-spin-resonance (ESR) spectroscopy on human tissue samples, treated with different CAP doses, enabled the measurement and the distribution of CAP-derived radicals in the tissues. The results correlate plasma dosage and the generation of radical species with cell viability and cell proliferation of primary human fibroblasts while demonstrating apoptosis-independent antiproliferative cell effects. Moreover, a dose-dependent increase of cells in the G1 phase of the cell cycle was observed, stressing the likely important role of cell cycle regulation for antiproliferative CAP mechanisms. This study introduces suitable methods for CAP monitoring on tissues and contributes to a better understanding of tissue-derived plasma effects of APPJs.