Defect engineering of enzyme-embedded metal–organic frameworks for smart cargo release

A biological system that can efficiently respond to external signals to release its cargo is promising in many areas. Here, we report a method of engineering defects in enzyme-embedded metal–organic frameworks (MOFs) which brings advantageous properties for drug delivery, showing that defects sometimes can bring out miraculous performances. The glucose oxidase (GOx) encapsulated in MOFs with defects displayed much higher apparent activity than that in normal MOFs. By the combination of Fourier transformation of extended X-ray absorption fine structures and molecular simulations, we proved that the defects generated mesopores and thus enhanced the enzyme substrate transportation. Based on this defect engineering approach, a drug delivery system was constructed by co-encapsulating GOx and insulin in defected MOFs. The insulin in defected MOFs can be efficiently released in response to a high glucose concentration while scarcely released with a low glucose concentration, providing a new possible route for intelligent insulin delivery.