Silica Capsules Templated from Metal–Organic Frameworks for Enzyme Immobilization and Catalysis

Abstract

Inspired by the unique biological microenvironments of eukaryotic cells, hollow capsules are promising to immobilize enzymes due to their advantages for physical protection and improved activity of enzymes. Herein, we report a facile method to fabricate silica (SiO2) capsules using zeolitic imidazole framework-8 nanoparticles (ZIF-8 NPs) as templates for enzyme immobilization and catalysis. Enzyme-encapsulated SiO2 capsules are obtained by encapsulation of enzymes in ZIF-8 NPs and subsequent coating of silica layers, followed by the removal of templates in a mild condition (i.e., ethylenediaminetetraacetic acid (EDTA) solution). The enzyme (i.e., horseradish peroxidase, HRP) activity in SiO2 capsules is improved more than 15 times compared to that of enzyme-loaded ZIF-8 NPs. Enzymes in SiO2 capsules maintain a high relative activity after being subjected to high temperature, enzymolysis, and recycling compared to free enzymes. In addition, multienzymes (e.g., glucose oxidase and HRP) can also be coencapsulated within SiO2 capsules to show a reaction with a high cascade catalytic efficacy. This work provides a versatile strategy for enzyme immobilization and protection with potential applications in biocatalysis.