The Potential of a Novel Cold Atmospheric Plasma Jet as a Feasible Therapeutic Strategy for Gingivitis—A Cell-Based Study

Due to its antimicrobial, anti-inflammatory and pro-healing properties, the application of cold atmospheric plasma (CAP) has emerged as a new and promising therapeutic strategy in various fields of medicine, including general medicine and dentistry. In this light, the aim of the present study was to investigate the effects of a homemade plasma jet on the cellular behaviour of two important cell types involved in gingivitis, namely gingival fibroblasts (HGF-1 cell line) and macrophages (RAW 264.7 cell line), by the direct application of CAP in different experimental conditions. The cellular behaviour of the HGF-1 cells was investigated in terms of viability/proliferation (LIVE/DEAD and CCK-8 assays), morphological features (immunofluorescent staining of the actin cytoskeleton) and fibronectin expression (immunocytochemical staining of the fibronectin network), while the macrophages' response was evaluated through the assessment of the cellular survival/proliferation rate (LIVE/DEAD and CCK-8 assays), morphological behaviour (immunofluorescent staining of the actin cytoskeleton) and inflammatory activity (pro-inflammatory cytokine secretion profile (ELISA assay) and foreign body giant cells (FBGCs) formation (immunofluorescent staining of the actin cytoskeleton and multinuclearity index determination)). The in vitro biological assessment revealed an upward trend dependent on treatment time and number of CAP applications, in terms of fibroblasts proliferation (<i>p</i> < 0.0001) and fibronectin expression (<i>p</i> < 0.0001). On the other hand, the macrophages exposed to five consecutive CAP applications for longer treatment times (over 120 s) exhibited a strong pro-inflammatory activity, as evinced by their altered morphology, pro-inflammatory cytokine profile (<i>p</i> < 0.0001) and FBGCs formation. Overall, our results demonstrate that CAP exposure, when used with appropriate operating parameters, has a beneficial effect on the cellular response of HGF-1 and RAW 264.7 cells, thus paving the way for further in vitro and in vivo investigations that will allow the translation of CAP treatment from research to clinic as an alternative therapy for gingivitis.