Enzyme shielding by mesoporous organosilica shell on Fe3O4@silica yolk-shell nanospheres.

Enzyme immobilization on the external surface of solid supports is a commonly adopted method to improve stability and reuse for continuous operations, which, however, is prone to cause the enzyme denaturation due to no carriers protection. Herein, we describe enzyme-shielding strategy to prepare hybrid organic/inorganic nanobiocatalysts; it exploits the self-assembly of silane building blocks at the surface of immobilized enzymes on Fe3O4/silica core-shell nanospheres to grow a protective silica layer. The silica shell around the immobilized enzyme particles provides a "shield" to protect from biological, thermal and chemical degradation for enzyme. As a result, the recycling of the immobilized catalase with a protective silica layer was improved remarkably compared with immobilized catalase without a protective silica layer. The immobilized catalase with a protective silica layer still remained 70% of their original activity after 9 cycles, whereas the immobilized catalase without a protective silica layer only retained 20% of their original activity. Moreover, the immobilized catalase with a protective silica layer exhibited significantly enhanced resistance to denaturing stresses (such as proteolytic agent, denaturants, and heat). Therefore, the enzyme-shielding strategy showed promising applications for preparing obtain stable and recycled nanobiocatalyst.