Monodisperse Selectively Permeable Hydrogel Capsules Made from Single Emulsion Drops

Abstract

Capsules are often used to protect chemical and biological entities from the environment, to control the timing and location of their release, or to facilitate the collection of waste. Their performance depends on the thickness and composition of their shells, which can be closely controlled if capsules are made from double emulsion drops that are produced with microfluidics. However, the fabrication of such double emulsions is delicate, limiting throughput and increasing costs. Here, a fast, scalable method to produce monodisperse microcapsules possessing mechanically robust, thin, semipermeable hydrogel shells from single emulsion drops is introduced. This is achieved by selectively polymerizing reagents in close proximity to the drop surface to form a biocompatible 1.6 μm-thick hydrogel shell that encompasses a liquid core. The size-selective permeability of the shell enables the growth of living yeast and bacteria in their cores. Moreover, if capsules are loaded with adsorbents, they can repetitively remove waste products from water. The simplicity and robustness of the capsule fabrication makes the process scalable and cost effective. It has thus the potential to extend the use of calibrated capsules possessing well-defined dimensions to cost sensitive fields, including food, waste water treatment, or oil recovery.

Direct encapsulation of biomolecules in semi-permeable microcapsules produced with double-emulsions

“…Effective removal of porogen in aqueous washes and other downstream processes affecting capsule permeability can be further improved to produce more homogeneous capsules. As controlling UV illumination initiating the polymerization process is critical for PIPS and generating the desired permeability, future developments could use in-line polymerization 15 to produce capsules to ensure uniform illumination of each double-emulsion droplet. Finally, matching the density between the different phases, modifying the shell thickness, as well as exploring different porogen, surfactant, and photoinitiator compositions will be required to produce capsules with tailored properties for other specific applications.…”

Soft and Tough Microcapsules with Double‐Network Hydrogel Shells

“…In particular, hydrogels have been tailored to a form of microshells through emulsion templating, compartmentalizing hollow cores. [ 14–19 ] The microcompartments are capable of molecular exchanges with the surrounding, thereby serving as advanced microcarriers for active ingredients, [ 20–29 ] including cells, [ 20,21 ] enzymes, [ 22–25 ] drugs, [ 26,27 ] and microsensors [ 28,29 ] in various applications. As the hydrogel shells have relatively short diffusion lengths in comparison with bulk counterparts, they show fast and efficient molecular exchange while securing well‐defined regulation of molecule‐selective permeation.…”

“…In particular, hydrogels have been tailored to a form of microshells through emulsion templating, compartmentalizing hollow cores. [14][15][16][17][18][19] The microcompartments are capable of molecular exchanges with the surrounding, thereby serving as advanced microcarriers for active ingredients, [20][21][22][23][24][25][26][27][28][29] including cells, [20,21] enzymes, [22][23][24][25] drugs, [26,27] and microsensors [28,29] in various applications. As stability.…”

Dielectrophoretic Characterization of Dynamic Microcapsules and Their Magnetophoretic Manipulation

“…Microcapsules are small particles containing a separate core and a shell phase that are of interest for encapsulation, protection, and delivery purposes of a sensitive cargo such as small molecules and biologics, including enzymes, proteins, and nucleic acids. − In liquid-core microcapsules, the cargo molecule can be suspended in the core under favorable conditions that keep it stable, while it is spatially separated from the shell membrane that controls the release function either through its permeability or an environmental destructive trigger event . Recently, reversibly stimuli-responsive “dynamic” microcapsules have been reported that exhibit a pH-triggered change of the shell’s permeability without its destruction, enabling repeated capture, trap, and release of cargo molecules over multiple cycles, as well as staggered on-demand release. − To gain a fundamental understanding of their response mechanism, an in-depth and direct characterization of the steady-state membrane properties in the permeable and impermeable states, as well as the transient response upon switch of the environmental stimuli, is required.…”