(185c) Computational Analysis of MOF-Enzyme Interactions for Next Generation of Sensitive Biosensors

Authors: 
Chapman, J., West Virginia University
Garapati, N., West Virginia University
Ismail, A. E., West Virginia University
Dinu, C. Z., West Virginia University
The advantages of biocatalysts, such as superior catalytic efficiency at mild reaction conditions and extremely high substrate specificity and product selectivity, have been partially employed in biomedical settings for next generation of biosensors or decontamination platforms. In such applications, enzyme immobilization has been shown to improve enzyme stability over broad ranges of temperatures and pH conditions while reducing temporal loss of enzyme activity and providing a means to separate biocatalysts from reaction mixtures for both analysis and reuse.

Metal-organic frameworks (MOFs) have been proposed with exceptional potential as carriers for highly active immobilized biocatalysts owing to their high degree of stability, tunability of surface features, high specific surface area, selective porosity, and synergistic catalytic efficiency when coupled with biocatalysts. Herein, we hypothesize that the immobilization of myeloperoxidase (MPO), a model enzyme that catalyzes production of hypohalous acids, to zeolitic imidazolate framework (ZIF-8) results in a highly efficient composite biocatalyst, thus making it an attractive option for biomedical implementation of detection of inflammation. The feasibility of the MOF-enzyme composites was ensured via a combinatorial approach in which favorable physical interactions between ZIF-8 and MPO as predicted by molecular dynamics (MD) simulations were corroborated with the experimentally determined interfacial kinetic parameters of MPO. The geometry of bulk ZIF-8 was energy-minimized to determine thermodynamically probable surface terminations of the MOF particle. MD studies also elucidated energy-preferred physisorption mechanisms of MPO to the surface of ZIF-8 while considering critical immobilization factors, i.e., substrate accessibility to enzyme active site, physiochemical interactions between the MOF and the enzyme, and resulting configurational changes of both MPO and ZIF-8 respectively. Kinetic studies of the MOF-enzyme composite were carried out to validate insights gathered from computational analyses and to further inform revisions to the immobilization strategy thus resulting in immobilized biocatalysts possessing optimal activity retention and operational stability. The results both highlight how the critical assessment of enzyme-carrier interactions at the molecular level is necessary for the implementation of fully optimized immobilized biocatalysts and demonstrate the viability of MOF-enzyme composites for such biomedical application. Further, the results provide a viable strategy for industrial implementation of enzyme-MOF composites in industrial hygiene and catalysis, as well as a niche in selective chemical production.