A Plasma-Functionalized ECM Platform for Intraoral Inflammation Control: Comparative Effects of Hyaluronic Acid and N-Acetyl-L-Cysteine on Oral Keratinocyte Response

Oral mucosal ulcers sustain a persistent inflammatory and oxidative microenvironment that interferes with epithelial repair and delays healing. Although hyaluronic acid (HA) is used in oral wound management due to its biocompatibility and hydrating properties, its biological activity is highly context-dependent and can be compromised under inflammatory conditions. In contrast, N-acetyl-L-cysteine (NAC) is a well-established antioxidant with documented anti-inflammatory effects, yet its rapid clearance limits its effectiveness when applied locally. In this study, the effects of HA and NAC, individually and in combination, on metabolic activity and inflammatory responses of TNF-α-stimulated human gingival keratinocytes were evaluated. In parallel, the individual immobilization of HA or NAC onto plasma-activated decellularized extracellular matrix (dECM) films was investigated as a materials-oriented approach for potential localized intraoral applications. NAC significantly attenuated TNF-α-induced IL-6 and IL-8 secretion, reducing both cytokines by approximately 99%, while preserving keratinocyte metabolic activity. HA displayed limited immunomodulatory effects. The combined HA + NAC condition did not improve the response compared with NAC alone. Plasma treatment enabled stable individual grafting of HA and NAC onto dECM films, and both functionalized surfaces retained chemical stability under saliva-like conditions. Collectively, these findings identify NAC as the most effective anti-inflammatory candidate under the tested cellular conditions and support plasma-functionalized dECM films as a feasible platform for future biological evaluation in intraoral applications.