Bifunctional Submicron Colloidosomes Coassembled from Fluorescent and Superparamagnetic Nanoparticles

Colloidosomes are microcapsules consisting of nanoparticle shells. These microcarriers can be self‐assembled from a wide range of colloidal particles with selective chemical, physical, and morphological properties and show promise for application in the field of theranostic nanomedicine. Previous studies have mainly focused on fairly large colloidosomes (>1 μm) based on a single kind of particle; however, the intrinsic building‐block nature of this microcarrier has not been exploited so far for the introduction of tailored functionality at the nanoscale. We report a synthetic route based on interfacial shear rheology studies that allows the simultaneous incorporation of different nanoparticles with distinct physical properties, that is, superparamagnetic iron oxide and fluorescent silica nanoparticles, in a single submicron colloidosome. These tailor‐made microcapsules can potentially be used in various biomedical applications, including magnetic hyperthermia, magnetic particle imaging, drug targeting, and bioimaging. Outwardly functional but empty inside: Bifunctional submicron colloidosomes (see picture) were coassembled from superparamagnetic iron oxide nanoparticles (SPIONs) and fluorescent‐dye‐doped silica nanoparticles (FSNPs) at the interface between water‐in‐oil‐emulsion droplets and then transferred by centrifugation to a fresh aqueous phase. These inherently rigid microcapsules feature a nanoporous shell and an aqueous core for active‐agent encapsulation.