Exploring Enzyme Immobilisation through Biomimetic Crystallisation

Abstract

Metal-Organic Frameworks (MOFs) have demonstrated they are promising materials for enzyme immobilisation. Biomimetic crystallisation of enzyme@MOF composites utilises biomacromolecules, including enzymes, as the nucleating agents to promote crystallisation of MOFs under mild reaction conditions. The enzyme@MOFs composites formed exhibit enhanced or retained catalytic performance, improved thermal stability, and better reusability compared to unprotected enzymes. Chapter one is a broad review of MOFs, including discussion of traditional and novel enzyme immobilisation strategies to synthesise enzyme@MOFs, microfluidic strategies, and an expansion into other related inorganic porous materials, specifically covalent organic frameworks, and hydrogen-bonded organic frameworks which may be employed for enzyme immobilisation. Chapter two reports the biomimetic crystallisation of four new carboxylate-based MOFs with horseradish peroxidase (HRP). The HRP@MOFs are shown to have variable crystal structures depending on pH and display enhanced thermal stability and improved reusability. Chapter three presents a microfluidic controlled biomimetic crystallisation technique for the continuous synthesis of homogeneous HRP@MOF particles. The homogeneous HRP@MOF particles synthesised were shown to have improved catalytic activity over the corresponding bulk synthesised materials, this was attributed to the homogenous particle size and morphology. Chapter four discusses attempted biomimetic crystallisation strategies for HRP embedded UiO 66 MOFs and the characterisation of catalytic performance of the HRP@UiO-66 MOFs generated. The reduced enzymatic activity of the HRP@UiO-66 MOFs illustrates that UiO-66 cannot be a suitable base material for enzyme immobilisation via biomimetic crystallisation. In chapter five, a strategy which physically embedded HRP@MOFs onto a PVC polymer membrane was explored to perform enhanced reusability and mechanical strength of biocatalysts. However, the enhanced hydrophobicity of hybrid material enlarged the diffusion limitation effect thus prohibiting the catalytic reaction. Chapter six summarises the results of chapter two to five and elaborates on any future work which could be carried out.

Date of Award	11 Feb 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Imogen Riddell (Main Supervisor) & Darren Willcox (Co Supervisor)