Polysaccharides-Directed Biomineralization of Enzymes in Hierarchical Zeolite Imidazolate Frameworks for Electrochemical Detection of Phenols

Biomineralization of enzymes inside rigid metal-organic frameworks (MOFs) is appealing due to its biocompatibility and simplicity. However, this strategy has hitherto been limited to microporous MOFs, leading to low apparent enzymatic activity. In this study, polysaccharide sodium alginate is introduced during the biomineralization of enzymes in zeolitic imidazolate frameworks (ZIFs) to competitively coordinate with metal ions, which endows the encapsulated enzyme with a 7-fold higher activity than that in microporous ZIFs. Mechanism investigation showed that the introduction of alginate generates hierarchical porous structures and enhances the hydrophilicity, which contributes to the enhanced activity of the enzyme. Moreover, the porous ZIFs protect the embedded tyrosinase under detrimental conditions, which allows for the fast detection of phenol, with the limit of detection of 0.03 mM (S/N = 3). Engineering the enzyme with MOFs to enhance its activity and stability is anticipated to extend its application in biocatalysis and biosensors.