Acorn Shell Extract-Functionalized Cotton Biomaterials: A Sustainable Platform with Biological Activities and Controlled Release for Skin Microbiota Dysregulation Conditions

Background/Objectives: Skin dysbiosis is associated with several dermatological disorders and is often accompanied by oxidative stress and inflammation. Bioactive textiles offer a promising strategy for localized skin health management; however, many currently available materials rely on synthetic or metal-based agents. This study aimed to develop sustainable cotton-based bioactive textiles functionalized with acorn shell (AS) extract, an agri-food by-product rich in phenolic compounds, and evaluate their biological performance potential for skin-contact applications in the management of skin dysbiosis conditions. Methods: Cotton fabrics were pre-treated with chitosan, a commercial cationic agent, or potassium alum and functionalized with AS extract using exhaustion or padding techniques. The resulting materials were assessed for antimicrobial activity against skin-associated bacteria, antioxidant capacity, anti-inflammatory activity in LPS-stimulated macrophages, cytocompatibility with keratinocytes and macrophages, and phenolic compound release under skin-mimicking conditions. Results: AS-functionalized cotton exhibited strong antimicrobial activity, particularly against Gram-positive bacteria, together with significant antioxidant and anti-inflammatory effects. All functionalized textiles maintained keratinocyte viability above established cytocompatibility thresholds, supporting their suitability for direct skin contact. Exhaustion-treated samples showed higher phenolic incorporation and release, resulting in enhanced biological performance, whereas padding-treated fabrics exhibited lower phenolic loading, more sustained release profiles, and comparatively reduced bioactivity. Conclusions: AS extract can be successfully incorporated into cotton textiles using industrially relevant finishing methods, generating multifunctional materials with antimicrobial, antioxidant, and anti-inflammatory properties while maintaining cytocompatibility. These findings support the potential of AS-functionalized cotton as a sustainable, plant-based skin-contact textile platform for localized management of skin-dysbiosis-associated conditions, with great relevance for dermatological and healthcare applications.