Controlled release systems have been developed to improve the efficacy of and patient compliance to many medicines. Many of these systems seek to control drug concentrations by providing a continuous and prolonged release of a therapeutic while reducing the dosing frequency, fluctuations in plasma levels and adverse side-effects . Successful sustained delivery systems have been developed for a range of different peptides (e.g. Lupron Depot and Bydureon BCise) by encapsulation into polymeric microparticles. To date, most conventional controlled release systems release therapeutics in a continuous, passive manner as a function of water imbibition and the extent of polymer degradation .