Supracapsules are spherical-like objects, comprised of nanocapsule building blocks. The ability to control the assembly of supracapsules opens up the possibility of integrating multiple functionalities within a single object. Since supracapsules have an internal multi-compartment structure, they can display programmable release kinetics and thus could act as powerful tools in therapeutic delivery. In a study led by our collaborators Dr. Minghan Hu and Prof. Lucio Isa, we have developed a procedure for droplet-templated supracapsule assembly.
In this process, nanocapsules are initially contained within an oil phase flow. When this oil flow converges with an aqueous flow, oil droplets are generated. If the oil phase is subsequently evaporated, the nanocapsules spontaneously aggregate to form a supracapsule. Control of the droplet-forming process can be used to tune the size of the supracapsules and their content.
Importantly, the properties of the nanocapsules are preserved in the formed supracapsules, but new collective properties also emerge. Most notably, programmable release profiles are found to be distinct from those of single-compartment capsules. Interestingly, supracapsules can also be disassembled into single-compartment units via ultra-sonication, yielding unusual “burst-release” properties.
In summary, our novel microfluidic-assisted assembly strategy enables fine control over the formation of supracapsules with user-defined properties, and represents a significant step in the development of smart nanomaterials for a wide range of biomedical applications.
Fabrication of supracapsules. (a) Assembly scheme of nanocapsules towards the fabrication of supracapsules by evaporation-induced self-assembly from emulsion droplet templates. The spheres of different colors (yellow, red and green) represent nanocapsules with different encapsulated cargoes. (b) Optical micrographs of supracapsules with a monodispersed size, as obtained by microfluidics. (c) SEM image of supracapsules after drying. (d) Cryo-SEM micrograph of the cross-section of a supracapsule after freeze-fracture. Scale bars are 20 μm, 5 μm, and 2 μm in panels (b), (c) and (d), respectively.
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