Hybrid microcapsules with tunable properties via Pickering emulsion templates for the encapsulation of bioactive volatiles

Abstract

Bioactive volatile molecules such as aldehydes, ketones, and other phytochemicals are important as flavors and fragrances in nature, as well as in industry. Because of the volatility of these molecules and their sensitivity to chemical degradation, the design of efficient delivery systems to control their stability and release has become an important research area. In this study, we fabricated organic–inorganic hybrid microcapsules with tunable properties for the encapsulation of volatile fragrance molecules by using oil-in-water emulsions stabilized with complex SiO₂ particles as templates. Two different types of SiO₂ particles, amorphous fumed SiO₂ and amino-functionalized SiO₂, were used to stabilize the oil droplets during emulsification and were immobilized in the robust shell under a subsequent interfacial reaction. These hybrid microcapsules revealed tunable droplet size and surface properties with different SiO₂ stabilizer components. The microcapsules also exhibited low permeability and excellent thermal stability for volatile molecular core liquids. Moreover, with the SiO₂ particles embedded in the shell, these hybrid microcapsules revealed different mechanical behaviors (brittleness and breakability) upon compression than in traditional polymer-based microcapsules. We believe the hybrid microcapsules presented here may be of great interest for several important applications in which the aim is to encapsulate and release bioactive volatile molecules using mechanical forces as the trigger.