Enhancing Oxidase-Catalyzed Biosensing via Hydrophobic ZIF-7 Nanomaterials: A Micro-Triphase Interface Approach

Electrochemical bioassays based on oxidase reactions are widely used in biological sciences and medical industries. However, the enzymatic reaction kinetics are significantly restricted by the poor solubility and slow diffusion rate of oxygen in conventional solid-liquid diphase reaction system. This limitation compromises the detection accuracy, linearity and reliability of oxidase-based bioassays. In this study, an effective solid‒liquid‒air triphase bioassay system is provided that uses ZIF-7 nanoparticles (ZIF-7 NPs) as oxygen nanocarriers. We constructed a solid-liquid-air triphase enzyme electrode by encapsulating ZIF-7 NPs within an oxidase network. The hydrophobic nature of ZIF-7 NPs provides localized oxygen supply by releasing pre-stored oxygen from its hydrophobic pores, thereby enhancing the kinetics of oxidase-catalyzed reactions. Consequently, compared to the conventional diphase system, the triphase system significantly improves the enzymatic reaction kinetics with a 21-fold higher maximum reaction rate (V_max) and expands the linear detection range for glucose from 2 mM to 20 mM, a 10-fold improvement. Furthermore, this triphase technique can be applied to the detection of other biomolecules, and the design strategy offers a new route to addressing the gas deficiency problem in catalytic reactions that involve gas consumption.