Significance: For exploiting synthetic glucose-responsive insulin delivery systems, challenges remain to demonstrate a strategy that would combine ( i ) fast responsiveness, ( ii ) ease of administration, and ( iii ) excellent biocompatibility. We have developed a novel glucose-responsive insulin delivery device using a painless microneedle-array patch containing hypoxia-sensitive hyaluronic acid-based vesicles. The vesicles quickly dissociate and release encapsulated insulin under the local hypoxic environment, caused by the enzymatic oxidation of glucose in the hyperglycemic state. This “smart insulin patch” with a new enzyme-based glucose-responsive mechanism can regulate the blood glucose of type 1 diabetic mice to achieve normal levels, with faster responsiveness compared with the commonly used pH-sensitive formulations, and can avoid the risk of hypoglycemia.

Enzymes underpin physiological function and exhibit dysregulation in many disease-associated microenvironments and aberrant cell processes. Exploiting altered enzyme activity and expression for diagnostics, drug targeting, and drug release is tremendously promising. When combined with booming research in nanobiotechnology, enzyme-responsive nanomaterials used for controlled drug release have achieved significant development and have been studied as an important class of drug delivery strategies in nanomedicine. In this review, we describe enzymes such as proteases, phospholipases and oxidoreductases that serve as delivery triggers. Subsequently, we explore recently developed enzyme-responsive nanomaterials with versatile applications for extracellular and intracellular drug delivery. We conclude by discussing future opportunities and challenges in this area.