Insights into the Interaction between Immobilized Biocatalysts and Metal–Organic Frameworks: A Case Study of PCN-333

Abstract

The immobilization of enzymes in metal–organic frameworks (MOFs) with preserved biofunctionality paves a promising way to solve problems regarding the stability and reusability of enzymes. However, the rational design of MOF-based biocomposites remains a considerable challenge as very little is known about the state of the enzyme, the MOF support, and their host–guest interactions upon immobilization. In this study, we elucidate the detailed host–guest interaction for MOF immobilized enzymes in the biointerface. Two enzymes with different sizes, lipase and insulin, have been immobilized in a mesoporous PCN-333(Al) MOF. The dynamic changes of local structures of the MOF host and enzyme guests have been experimentally revealed for the existence of the confinement effect to enzymes and van der Waals interaction in the biointerface between the aluminum oxo-cluster of the PCN-333 and the -NH 2 species of enzymes. This kind of host–guest interaction renders the immobilization of enzymes in PCN-333 with high affinity and highly preserved enzymatic bioactivity.

Confining enzymes in porous organic frameworks: from synthetic strategy and characterization to healthcare applications

“…For instance, recently, Huang and co-workers for the first time reported the utilization of multi-nuclei 1D and 2D ssNMR and multiple-quantum, double-resonance, and relaxation ssNMR measurements to elucidate the detailed host–guest interaction between lipase or insulin and a mesoporous PCN-333 (Al) MOF. 207 The longer 1 H spin–lattice relaxation times ( T 1 ) of enzyme@PCN-333 preliminarily demonstrated a reduction in framework flexibility due to the enzyme confinement effect. Interestingly, the T 1 relaxation time of 27 Al decreased rather than increased after enzyme immobilization, suggesting the possible interaction between the Al-oxo clusters and enzymes, which resulted in the relaxing of the coordination bonds between Al-oxo and the organic linkers.…”

“…From a mechanism point of view, this fundamentally results from the interactions between the host and enzyme. Besides the aforementioned techniques to probe the enzyme conformation, techniques such as Raman spectroscopy, 206 solid-state UV-vis, 169 XPS 197 and ssNMR 207 are often used to study the nano-bio-interface interactions. For instance, recently, Huang and co-workers for the first time reported the utilization of multi-nuclei 1D and 2D ssNMR and multiple-quantum, double-resonance, and relaxation ssNMR measurements to elucidate the detailed host–guest interaction between lipase or insulin and a mesoporous PCN-333 (Al) MOF.…”

Enzyme‐Immobilized Metal‐Organic Frameworks: From Preparation to Application

“…[5] It can be attributed to the enhanced interaction between framework host and enzyme guest. [9] Therefore, MOFs are potentially the superior material for immobilized enzymes compared to other materials, which have been applied in gas storage, [10] separation, [11] sensing, [12] biological imaging, catalysis, [13] and drug delivery, [5] etc.…”

“…Besides, MOFs have been proved to improve the properties of enzymes, including catalytic activity, thermal stability, pH stability, organic solvent stability, recyclability, etc [5] . It can be attributed to the enhanced interaction between framework host and enzyme guest [9] . Therefore, MOFs are potentially the superior material for immobilized enzymes compared to other materials, which have been applied in gas storage, [10] separation, [11] sensing, [12] biological imaging, catalysis, [13] and drug delivery, [5] etc.…”

Metal Organic Frameworks for Bioelectrochemical Applications

“…Pore sizes including pore apertures must of course be carefully considered and compatible with the size of the enzyme. Spectroscopic techniques such as Raman spectroscopy and solid-state NMR have been effectively employed to further understand enzyme confinement, for example, to observe specific MOF-enzyme interactions [14] .…”