Clay-carvacrol nanoemulsions for wound healing: Design and characterization studies

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One of the current challenges of scientific research is the design of advanced wound care to obtain a rapid and complete healing of chronic wounds, thus avoiding serious complications. With this purpose, a great deal of attention has been paid to Carvacrol (CRV), a monoterpene and one of the main components of the essential oils of Oregano, Thyme and Satureja Montana. Despite its promising properties in wound treatment, CRV exhibits high lipophilicity, rapid oxidation and volatilization, and inadequate retention time at the site of action, which limit its therapeutic application. A possible technological strategy to overcome these disadvantages could involve the preparation of CRV-based oil in water nanoemulsions (O/W NE) in which CRV itself is used both as the oil phase and as the active compound. CRV-NE uncoated or coated by Chitosan were prepared and deeply characterized. In particular, stability studies were carried out in order to observe some parameters such as dimensions, ζ-Potential, pH and CRV amount at different temperatures over 90 days. Furthermore, the size was evaluated by DLS analyses and compared with data obtained by TEM observations. Secondly, two clay minerals (a montmorillonite and a sepiolite, VHS and PS9 respectively) were added to the NE in order to increase the final viscosity, thus obtaining a semisolid formulation. The rheological properties of the formulations were also studied, in particular, NE and NE-Ch samples were analyzed for 3 months while NE-Ch-VHS, NE-Ch-PS9 for 1 month. Finally, the biocompatibility of CRV-NE, as well as its antioxidant and anti-inflammatory properties, were proved in vitro on fibroblasts and macrophages.