Understanding and Engineering the Nucleation of Enzyme Metal-Organic Frameworks

Enzymes are natural catalysts that can be used by chemical industries to speed up the rate of reactions and reduce the energy requirements of catalytic processes. However, enzymes are not typically stable outside of the physiological environment in which they evolved, significantly limiting their utility for industrial applications. A potential solution to this problem is to immobilize enzymes onto support structures.

The ideal support material must be capable of loading high quantities of the active form of the enzyme. The support should also increase the stability and recyclability of the enzyme compared to the free enzyme in solution. Metal-organic frameworks (MOFs) are a promising class of materials for enzyme immobilization.

MOFs are porous crystalline materials formed by the self-assembly of metal ions and organic ligands. Enzymes can be immobilized on MOFs by simply mixing the metal, ligand, and enzyme in aqueous solutions at room temperature. The enzymes are then incorporated into the MOF framework during the nucleation and growth processes.

Understanding how this process works requires a detailed analysis of the system's nucleation and growth mechanisms. This fundamental mechanistic knowledge will provide robust design rules for the synthesis of enzyme-immobilized MOFs with high loading of the active form of the enzyme. The ability to immobilize practically any enzyme at the MOF surface has the potential to revolutionize the biotechnology industry and benefit society through lower energy chemical processes.

The investigator will also develop a mobile K-12 outreach activity that uses low-cost microscopy to observe salt crystal growth.

This project aims to determine the nucleation and growth mechanisms of enzyme MOF composite materials. The approach employs cryogenic and liquid-phase electron microscopy. Cryogenic electron microscopy will be used to trap intermediates and analyze their high-resolution structure.

Liquid-phase electron microscopy will be used to monitor the kinetics of absorption, nucleation, and growth. The electron microscopy data will be supported by bulk scattering analysis using light and X-rays. The knowledge gained from these mechanistic studies will be used to re-engineer the interfacial chemistry to improve both encapsulation efficiency and enzymatic activity.

The project will reveal the formation mechanisms, how the mechanisms can be manipulated by tuning the interfacial chemistry, and the structure-property relationships.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.