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

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.