Alkylpolyglucoside-Stabilized Oleic Acid Nanodroplets as a Sustainable Platform for the Aqueous Dispersion of Essential Oil Compounds

Abstract

The encapsulation of hydrophobic bioactive molecules, such as essential oil compounds (EOCs), in aqueous nanodispersions is critical for enhancing their solubility, stability, and applicability across diverse industries. This study examines the formulation of oleic acid nanodroplets stabilized by a biobased alkylpolyglucoside (APG), without the need for auxiliary cosurfactants. In this system, oleic acid simultaneously provides the oil core and contributes to interfacial charging, enabling the nanodroplets to act as efficient carriers for thymol and carvacrol. In contrast to conventional formulations requiring cosurfactants, this work presents a simplified and greener approach. A pseudoternary phase diagram defined the regions of stable dispersion formation, confirming the feasibility of a one-surfactant-only system. Dynamic light scattering confirmed a monomodal size distribution (10–15 nm), whereas fluorescence spectroscopy revealed up to three distinct chemical environments for the EOCs within the droplets. Crucially, the system’s stability is governed by the pH-dependent dissociation of oleic acid at the interface, as elucidated by conductivity and pH measurements. The results demonstrate that increasing EOC concentration leads to droplet growth, which may destabilize dispersions, highlighting the need for compositional optimization. This APG/oleic acid platform provides a scalable, eco-friendly alternative for delivering poorly soluble bioactives, aligning with the principles of sustainable chemistry and reducing the environmental footprint of essential oil formulations.