In situ complex coacervation supported by self-coated polydopamine interlayer on uniform-sized essential oils droplet

Hypothesis: Essential oils (EOs) are common additives in daily products by virtue of their olfactory, physicochemical, and biological characteristics. However, EOs are physicochemically unstable and susceptible to degradation or loss, leading to limited shelf life and inadequate efficacy. Herein we propose a new bi-layered encapsulation structure in combination with complex coacervation and self-coating of polydopamine (PDA) on membrane emulsified mono-dispersion of EOs droplets.Experiments: A mono-dispersed EOs emulsion stabilized by nonionic surfactants was produced by membrane emulsification, wherein the EOs droplets were applied as soft templates to deposit a superficial PDA layer. Under alkaline conditions, gelatin (GE) was bound to the PDA layer and further applied as in situ coacervation sites for gum Arabic (GA). Structural identification and morphological observation proved the successful preparation of bi-layered EOs capsules.Findings: Compared with traditional complex coacervation strategies, current novel bi-layered capsules showed significantly improved structural stability, thermal stability, providing better protection of EOs with sustained release properties. Moreover, the encapsulation efficiency and loading content were both proved higher for the bi-layered system. The first report on PDA-coating onto surfactants-absorbed macroemulsion droplets also provides an in-depth insight into applying PDA as versatile intermediate functional biomaterials.(c) 2022 Elsevier Inc. All rights reserved.