Development and characterization of a nanoemulsions-based semi-solid platform: Physicochemical properties, antioxidant and antimicrobial activities

Staphylococcus aureus infection is a major contributor to chronic non-healing wounds, where persistent bacterial colonization and biofilm formation impair tissue repair and sustain prolonged inflammation. To counteract S. aureus skin colonization, levofloxacin (LVX)-loaded nanoemulsions (NEsL) were formulated using lentisk (Pistacia lentiscus) oil (LO) as the oily phase and incorporated into an advanced chitosan-based formulation (AF). The nanoemulsions combined the capacity to solubilize LVX, a lipophilic antibiotic used as a drug model, with the intrinsic antimicrobial activity of LO, employed as an active excipient. Both unloaded and drug-loaded NEsL were characterized in terms of particle size, biocompatibility, and antioxidant activity, demonstrating suitable physicochemical and biological properties. The AF was assessed for stability over time, film thickness, and adhesive performance; all formulations exhibited satisfactory bioadhesive properties and stability, supporting their potential for topical skin application. In vitro and ex vivo permeation experiments on LVX-containing samples were conducted using a Franz diffusion cell system to evaluate drug permeation profiles and skin localization. Based on these findings, the most promising formulation, NEsL and AF loaded with NEsL (AF-NEsL), was selected and tested for its ability to counteract S. aureus skin colonization. Enhanced antimicrobial performance was observed exclusively when NEsL was incorporated into the AF matrix, compared to either NEsL or AF-NEs alone. Taken together, this bioadhesive nanoplatform based on bioactive nanocarriers may represent a promising approach for localized topical delivery, although its therapeutic efficacy requires further investigation.