A novel two-dimensional metal imidazolate sulphate framework as a versatile platform for enzyme immobilization

Area of Science:

• Materials Science
• Biotechnology
• Chemical Engineering

Background:

• Enzyme encapsulation in ZIF-8 (zeolitic imidazolate frameworks) via co-precipitation is a key technique.
• Conventional 3D ZIF-8 composites often suffer from reduced enzyme activity due to structural limitations and precursor protonation.
• Protonation of 2-methylimidazole (2-MeIm) in ZIF-8 synthesis can negatively impact enzyme performance.

Purpose of the Study:

• To develop a novel 2D enzyme@ZIF composite as an alternative to 3D ZIF-8.
• To enhance enzyme activity, loading, and stability through a modified encapsulation strategy.
• To investigate the impact of a 2D structure and modified precursor on enzyme immobilization.

Main Methods:

• Synthesis of 2D catalase@ZIFs(SO4) composites using a co-precipitation method.
• Partial replacement of 2-methylimidazole (2-MeIm) with sulfate during enzyme immobilization.
• Characterization of the 2D composite structure and comparison with 3D counterparts.
• Immobilization of other enzymes including glucose oxidase, glutamate oxidase, and phenylalanine ammonia lyase.

Main Results:

• The 2D catalase@ZIFs(SO4) composite showed a nine-fold increase in activity and three-fold higher enzyme loading compared to 3D catalase@ZIF-8.
• The 2D structure and use of sulfate improved the hydrophilic microenvironment and facilitated substrate transfer.
• Immobilized enzymes exhibited enhanced pH tolerance, thermal stability, resistance to denaturants, and storage stability.
• The approach was validated with other enzymes, all showing increased activity.

Conclusions:

• A novel 2D enzyme@ZIFs(SO4) composite platform significantly enhances enzyme activity and stability.
• The 2D structure and modified precursor strategy overcome limitations of traditional 3D ZIF-8 enzyme encapsulation.
• This versatile method offers a promising approach for advanced enzyme immobilization applications.