Work

Gelled Oil-in-Water Microemulsions Stabilized with Natural Surfactant Decyl Glucoside as Cutaneous Nanocarriers for Cinnamon Bark Essential Oil: Formulation and Comprehensive Pharmacotechnical Characterization

Year: 2026

Type: article

Abstract: Background/Objectives: Cinnamon bark essential oil (CEO) possesses antimicrobial, antioxidant, and anti-inflammatory properties. However, its topical application is limited by poor aqueous solubility, volatility, and chemical instability. The aim of this study was to develop gelled oil-in-water microemulsions stabilized with Decyl Glucoside for the cutaneous delivery of CEO and to evaluate their physicochemical and pharmaceutical characteristics. Methods: Pseudoternary phase diagrams were constructed to identify the microemulsion regions using Decyl Glucoside, propylene glycol, CEO, isopropyl myristate, and water. Selected CEO-loaded microemulsions were characterized in terms of droplet size, polydispersity index, zeta potential, refractive index, viscosity, and apparent pH, and were subsequently gelled with Aerosil® 200. The resulting gelled microemulsions were evaluated for CEO content, apparent pH, rheological and textural properties, spreadability, in vitro release and skin permeation studies. The short-term stability of both liquid and gelled microemulsions was also assessed over 45 days. Results: Three CEO-loaded oil-in-water microemulsions were selected from the isotropic regions of the pseudoternary phase diagrams and successfully transformed into homogeneous gelled systems without phase separation. CEO incorporation increased the storage modulus and yield stress of the gelled formulations compared with the corresponding blank systems. The surfactant-to-cosurfactant ratio markedly influenced the rheological properties, mechanical strength, and in vitro release and skin permeation of CEO. Among the investigated formulations, MEG-CEO-2 provided the best balance between mechanical properties, CEO release, and skin permeation. Both liquid and gelled microemulsions maintained their principal physicochemical characteristics during the 45-day stability assessment. Conclusions: Decyl Glucoside-stabilized gelled microemulsions exhibited physicochemical and pharmaceutical properties supporting their further investigation as topical delivery systems for CEO. The results demonstrate that the surfactant-to-cosurfactant ratio can be used to tailor formulation performance, supporting a rational approach for the development of CEO-loaded dermal delivery systems. However, preservation of the biological activities of CEO following incorporation into these systems remains to be experimentally established.

Source: Pharmaceutics

DOI: 10.3390/pharmaceutics18101317