Microfluidically produced microcapsules with amphiphilic polymer conetwork shells

Microcapsules with aqueous core can be conveniently prepared by water-in-oil-in-water double emulsion microfluidics. However, conventional shell materials are either based on polymers or monomers that are soluble in the oil phase, or based on hydrophobic colloidal particles. As a result, microcapsules derived from double emulsions usually feature a hydrophobic shell that is not semipermeable for water-soluble compounds. While capsules with semipermeable hydrogel shells have been demonstrated, these may exhibit poor mechanical properties and lack the robustness required in many applications. In this study, amphiphilic polymer conetworks (APCNs) based on poly(2-hydroxyethyl acrylate)-linked by-polydimethylsiloxane (PHEA-l-PDMS) are introduced as a new class of wall materials in double emulsion microcapsules. These APCNs are mechanically robust silicone hydrogels that are swellable and permeable to water, and are soft and elastic in the dry and swollen states. Thus, the microcapsules can be dried and rehydrated multiple times or shrunken in sodium chloride salt solutions without getting damaged. Moreover, the APCNs are semipermeable for hydrophilic organic compounds, while being impermeable for macromolecules and colloids. Thus, they can be loaded with macromolecules or nanoparticles during microfluidic formation, and with organic molecules after capsule synthesis. Uptake into and release from the capsules were studied with the model compounds fluorescein and fluorescently labelled dextran. Moreover, the microcapsules served as microreactors for catalytically active platinum nanoparticles that decomposed hydrogen peroxide. Finally, the surface of APCN microcapsules can be selectively functionalized with a cholesterol-based linker that non-covalently binds to the hydrophobic domains of the APCN. Thus, APCN microcapsules represent versatile and broadly applicable capsules that could find application for the controlled delivery of drugs, as microreactors for synthesis, or even as scaffolds for synthetic cells.