Managing diabetes can be a challenge. Usually, blood glucose levels need to be measured frequently, followed by the injection of an appropriate amount of insulin. A drug delivery system that can sense glucose levels and release insulin in a self-regulated way would be very useful.

Existing glucose-responsive systems are based on glucose oxidase (GOx), an enzyme which converts glucose to gluconic acid and hydrogen peroxide. The produced hydrogen peroxide can then trigger insulin release from suitable materials. However, it is usually difficult and time-consuming to produce this type of drug delivery system.

Fanggui Ye, Shulin Zhao, Guangxi Normal University, Guilin, China, and colleagues have developed a glucose-responsive metal-organic framework (MOF)-based drug delivery nanosystem that can easily be synthesized in a one-pot process. The team used the pH-responsive zeolitic imidazolate framework-8 (ZIF-8) to encapsulate GOx and insulin in a self-assembly process.

When the system is exposed to high levels of glucose, the sugar molecules enter the pores of the MOF and react with the GOx enzyme. The resulting increased H₂O₂ levels lower the pH value, which leads to decomposition of the MOF particles and release of the encapsulated insulin. The MOF-based delivery system has fast response times and is biocompatible, which was confirmed by tests on HeLa cells. Once the glucose levels are lowered, the insulin release decreases significantly, which avoids the risk of hypoglycemia. The system could potentially be used in the form of subcutaneous injections, which would be less frequent than pure insulin injections.

• One-pot synthesis of metal-organic framework-based drug carrier for intelligent glucose-responsive insulin delivery,
  Yan Duan, Fanggui Ye, Yuanlin Huang, Yuemei Qin, Caimei He, Shulin Zhao,
  Chem. Commun. 2018.
  https://doi.org/10.1039/c8cc02708k