pH-sensitive MOF integrated with glucose oxidase for glucose-responsive insulin delivery.

Glucose-responsive insulin delivery system mimicking the function of pancreatic β-cells to maintain blood glucose homeostasis would effectively alleviate diabetes. Here, a new glucose-responsive delivery (ZIF@Ins&GOx) for self-regulated insulin release was constructed by encapsulating insulin and glucose oxidase (GOx) into pH-sensitive zeolitic imidazole framework-8 (ZIF-8) nanocrystals. After entering the cavities of ZIF-8, glucose can be oxidized into gluconic acid by GOx, causing a decrease in local pH. Then, ZIF-8 nanocrystals would be degraded under the acidic microenvironment that in turn triggers the release of insulin in a glucose responsive fashion. In vitro studies indicated that the biological activity of insulin could be protected by the rigid structure of ZIF-8 and the release of insulin could be modulated in response to glucose concentrations. In vivo experiments demonstrated that a single subcutaneous injection of the ZIF@Ins&GOx would facilitate the stabilization of blood glucose level of normoglycemic state for up to 72 h in type 1 diabetes (T1D). The multifunctional insulin delivery system shows a new proof-of-concept for T1D treatment by using ZIF-8 nanocrystals loaded with insulin and enzyme.