Intrinsic Catalytic Activities from Single Enzyme@Metal-Organic Frameworks by Using a Stochastic Collision Electrochemical Technique.

Enzymes encapsulated in metal-organic frameworks (enzyme@MOFs), as a promising immobilized enzyme, were investigated for intrinsic catalytic activities at the single entity level via a stochastic collision electrochemical technique. Zeolitic imidazolate frameworks with amorphous (aZIF-8) and crystalline (ZIF-8) structures were chosen as model MOFs to encapsulate glucose oxidase (GOx). We carried out single enzyme@MOF nanoparticle (NP) collision experiments using the carbon ultramicroelectrode (CUME), which demonstrated that the catalytic activity of GOx@ZIF-8 NPs was much less than GOx@aZIF-8 NPs. Meanwhile, the kcat and TON per GOx in aZIF-8 NPs were obtained, revealing the intrinsic catalytic activity of GOx in aZIF-8 NPs at the single entity level. This strategy is the first approach for investigating enzyme@MOFs at a single entity level, which can not only broaden the horizons of single entity electrochemistry (SEE) but also provide further insights into research on electrochemistry, catalysis, and nanocomposites.