Insight into Bioactivity of In‐situ Trapped Enzyme‐Covalent‐Organic Frameworks

Abstract

Selecting a suitable support material for enzyme immobilization with excellent biocatalytic activity and stability is a critical aspect in the development of functional biosystems. The highly stable and metal‐free properties of covalent‐organic frameworks (COFs) make them ideal supports for enzyme immobilization. Herein, we constructed three kinds of COFs via a biofriendly and one‐pot synthetic strategy at room temperature in aqueous solution. Among the three developed COFs (COF‐LZU1, RT‐COF‐1 and ACOF‐1), the horseradish peroxidase (HRP)‐incorporated COF‐LZU1 is found to retain the highest activity. Structural analysis reveals that a weakest interaction between the hydrated enzyme and COF‐LZU1, an easiest accessibility by the COF‐LZU1 to the substrate, as well as an optimal conformation of enzyme together promote the bioactivity of HRP‐COF‐LZU1. Furthermore, the COF‐LZU1 is revealed to be a versatile nanoplatform for encapsulating multiple enzymes. The COF‐LZU1 also offers superior protection for the immobilized enzymes under harsh conditions and during recycling. The comprehensive understanding of interfacial interactions of COF host and enzyme guest, the substrate diffusion, as well as the enzyme conformation alteration within COF matrices represents an opportunity to design the ideal biocatalysts and opens a broad range of applications of these nanosystems.

Improving the Bioactivity and Stability of Embedded Enzymes by Covalent Organic Frameworks

“…As a kind of sister material of MOFs in reticular chemistry, COFs are connected by strong organic covalent bonds with higher stability, and more importantly, the metal-free nature of COFs offers an excellent opportunity to avert the effects of metal ions. − Several green methods have been reported for de novo constructing enzymes@COFs biocomposites. − The Chen group reported a universal water-based in situ assembly strategy for fabricating various enzymes@COFs, which can be easily scaled up (2.3 g per reaction) . The Ouyang group incorporated enzymes within COFs by a greener and more convenient mechanochemical encapsulation, and Kim de novo embedded enzymes in COFs by using a deep eutectic solvent as the solvent. , In addition, the catalytic performances of enzymes@COFs can be optimized via the intrinsic property of COFs or the interfacial interactions of enzymes and COFs. − However, the superiority of COFs in enhancing enzymatic activity, especially including their metal-free nature, has not been fully explored, which is vital for understanding and optimizing their catalytic performance.…”