Facile Preparation of Silica/Tannic Acid/Zein Microcapsules Templated from Non-Aqueous Pickering Emulsions and their Application in Cargo Protection

Microcapsules have attracted significant attention in academia and industry due to their unique properties for protecting and controlling the release of active substances. However, based on water-insoluble biopolymers, developing a straightforward approach to prepare microcapsules with improved biocompatibility and functional shells remains a great challenge. In this study, zein, a water-insoluble protein, is employed to prepare robust microcapsules facilely using oil-in-aqueous ethanol Pickering emulsions as templates. First, the emulsion template is stabilized by hydrophobic silica nanoparticles with in situ surface modification of tannic acid. The zein is then precipitated at the interface in a controlled manner using antisolvent approach to obtain silica/tannic acid/zein (STZ) microcapsules. It is found that the concentration of zein and the presence of tannic acid played a significant role in the formation of STZ microcapsules with well-defined morphology and a robust shell. The uniform deposition of zein on the surface of template droplets is facilitated by the interactions between tannic acid and zein via hydrogen bond and electrostatic force. Finally, the resulting STZ microcapsules showed super resistance to ultraviolet (UV) radiation and high temperature for the unstable, lipophilic, and active substance of beta-carotene. A simple and controllable method is established for preparing oil droplet-filled silica nanoparticle/tannic acid/zein microcapsules using a non-aqueous Pickering emulsion template. Furthermore, the encapsulation and protection of a lipophilic and active compound, beta-carotene, within the filled oil droplets is demonstrated. image