Abstract
Nanoemulsions have become ideal candidates for loading hydrophobic active ingredients and enhancing their bioavailability in the pharmaceutical, food, and cosmetic industries. However, the lack of versatile carrier platforms for nanoemulsions hinders advanced control over their release behavior. In this work, a method is developed to encapsulate nanoemulsions in alginate capsules for the controlled delivery of lipophilic active ingredients. Functional nanoemulsions loaded with active ingredients and calcium ions are first prepared, followed by encapsulation inside alginate shells. The intrinsically high viscosity of the nanoemulsions ensures the formation of spherical capsules and high encapsulation efficiency during the synthesis. Moreover, a facile approach is developed to measure the nanoemulsion release profile from capsules through UV–vis measurement without an additional extraction step. A quantitative analysis of the release profiles shows that the capsule systems possess a tunable, delayed‐burst release. The encapsulation methodology is generalized to other active ingredients, oil phases, nanodroplet sizes, and chemically crosslinked inner hydrogel cores. Overall, the capsule systems provide promising platforms for various functional nanoemulsion formulations.
Highlights
The MIT Faculty has made this article openly available
We have developed versatile and functional capsule systems for controlled delivery of nanoemulsions that contain lipophilic active ingredients
The large viscosity prevents the dripped droplets from deformation due to the drag force exerted by the surrounding alginate solution
Summary
With an ideally high viscosity, the nanoemulsion dispersion can be encapsulated into uniformly spherical alginate capsules (Figure 2a). Previous work finds a similar trend and explained that a higher calcium concentration across the shell leads to a larger gradient for calcium ions to diffuse out, and a thicker shell can be formed.[38] Holding wCaCl2 constant at a value of 0.04, dispensing tips with different sizes are utilized to control inner core radii. This indicates that the hydrogel degradation process is uniform across the shell and can be characterized as bulk erosion.[48] For the bursting capsule, a crack forms on the shell, and the osmotic pressure between the two sides of the capsule drives the nanoemulsion to release out (Figure 3g). The empty capsule after the release can exist for a few minutes before complete degradation (Figure 3h)
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