Stable MOF@enzyme composites for electrochemical biosensing devices

Abstract

Naturally occurring enzymes are highly selective and efficient catalysts but given their intricate and fragile structure, wide application of their extraordinary catalytic potential in industrial and biomedical settings is highly desirable yet challenging. In this work we demonstrate this possibility using a facile, single-step technique for metal–organic framework (MOF) biomimetic mineralisation of three different enzymes of industrial interest; glucose oxidase (GOx), organophosphate degrading enzyme A (OpdA) and α-chymotrypsin. We investigate the thermal stability of the resulting ZIF-8@enzyme composites at temperatures in the industrially relevant range of 50–80 °C with time ranging from minutes to hours. In situ thermal stabilisation analysis was performed at the small angle X-ray scattering (SAXS) beamline to understand the effect of temperature on the ZIF-8@GOx composite. Furthermore, we illustrate the electrochemical operational stability of a ZIF-8@GOx modified electrode at challenging elevated temperatures validating its potent application in electrochemical devices. The resulting optimized and ultra-stable amperometric glucose biosensor demonstrates a clinically relevant wide linear range of 1–10 mM glucose with a detection limit of 0.05 mM. The biosensor demonstrates robust performance and selectivity with insignificant interference effects in the presence of 100 μM uric acid, acetaminophen and ascorbic acid, respectively, and satisfactory operation in up to 20% serum environment.