Active droplets in a hydrogel release drugs with a constant and tunable rate

Materials that release drugs with a constant, zero-order rate are of great importance to improve therapeutic efficacy and reduce toxic side effects. The development of such materials is challenging, particularly the development of versatile platforms of which the release rate can be tuned. Here, we report a platform that comprises active oil-droplets with a tunable lifetime embedded in a hydrogel. The oil droplets are a type of dissipative (dynamic) assembly that is formed by a fuel-driven chemical reaction cycle. Once the fuel is depleted, the oil droplets decay following zero-order reaction kinetics due to a unique self-protection mechanism. We entrap hydrophobic drugs in the oil-phase, and we use the zero-order decay to dictate the release profiles of the entrapped drugs. The drug release has a constant rate over most of the release period, which is unique for drug delivery vehicles, particularly when considering the simplicity of the design. Moreover, we can tune the rate of the drug release and the length of the release period.