Triggered Release of Loads from Microcapsule-in-Microcapsule Hydrogel Microcarriers: En-Route to an “Artificial Pancreas”

A method to assemble stimuli-responsive nucleic acid-based hydrogel-stabilized microcapsule-in-microcapsule systems is introduced. An inner aqueous compartment stabilized by stimuli-responsive hydrogel-layer (ca. 150 nm) provides the inner microcapsule (diameter ca. 2.5 µm). The inner microcapsule is separated from the outer aqueous compartment stabilized by an outer stimuli-responsive hydrogel layer (thickness of ca. 150 nm) that yields a micro-capsule-in-microcapsule system. Different loads, e.g. tetramethyl rhodamine-dextran (TMR-D) and CdSe/ZnS quantum dots (QDs), are loaded in the inner and outer aqueous compartments. The hydrogel layers exist in a higher stiffness state that prevents inter-reservoir or leakage of the loads from the respective aqueous compartments. Subjecting the inner hydrogel layer to Zn2+-ion and/or the outer hydrogel layer to acidic pH or crown ether leads to the triggered separation of the bridging units associated with the respective hydrogel layers. This results in hydrogel la...