Immobilization on Metal-Organic Framework Engenders High Sensitivity for Enzymatic Electrochemical Detection

The protection effect of metal-organic framework (MOF) provides high stability for immobilized enzyme. The small cavities of MOFs, however, usually result in decreased apparent substrate affinity and enzymatic activity of immobilized enzyme, compared to native enzyme. We synthesized zeolitic imidazolate framework-8 (ZIF-8) with a combination of mesoporous and microporous channels for cytochrome c (Cyt c) immobilization. Compared with native Cyt c, the immobilized Cyt c displayed increased apparent substrate affinity (Michaelis constant K_m reduced by ∼50%), ∼128% increased enzymatic activity, and 1.4-fold increased sensitivity in the enzymatic electrochemical detection of H₂O₂. The immobilized Cyt c-coated screen-printed electrode was applied for the fast detection of residual H₂O₂ in microliter food samples such as milk and beer, making it promising for the development of efficient biosensors.