(168d) Rational Design of Mimic Multi-Enzyme Systems in Hierarchically Porous Biomimetic Metal-Organic Frameworks

Enzymes are the most sophisticated
macromolecular biological catalysts in living organisms, and can catalyze a
wide variety of reactions with excellent efficiency and specificity.In
natural systems, multi-enzyme systems constituted by several kinds of enzymes
ensure the process of cascade reactions
and help accomplish various physiological processes and superior properties. Metal-organic
frameworks (MOFs), self-assembled from metal cations or clusters and organic
linkers, have drawn extensive research interest as candidates for enzyme immobilization
owing to their tunable porosity, large and accessible specific surface areas,
and excellent chemical/thermal stability. A variety of mimic multi-enzyme
systems have been constructed in which the MOFs worked as the immobilization matrix
containing multiple natural enzymes. Moreover, with the deeper study and understanding
of MOF materials, a variety of MOFs with intrinsic mimic enzyme catalysis have
been developed, possessing high catalytic activity and stability. For example,
the integration of metalloporphyrins such as ferriporphyrin into MOFs gave rise
to effective peroxidase mimics. These MOF mimics could be utilized for
constructing artificial enzyme systems with natural enzymes for tandem
catalysis and offer new opportunities to study the cooperation between the
natural enzymes and mimics. Recently, hierarchically porous MOFs (HP-MOFs) have
been developed and attracted broad attention, due tothe large mesopores and
high surface area which could en-capsulate large molecules more efficiently. In
this work, hierarchically porous biomimetic MOF HP-PCN-224(Fe) was successfully
synthesized with a modulator-induced defect-formation strategy. The modulator was
then removed by hydrochloric acid treatment, thus giving rise to relatively
large mesoporous. HP-PCN-224(Fe) can immobilize enzymes with high load capacity
and excellent stability. More importantly, HP-PCN-224(Fe) not only acts as the
enzyme immobilization matrix, but also as an effective peroxidase mimic in the
mimic multi-enzyme systems. GOx@HP-PCN-224(Fe) was obtained by immobilizing
glucose oxidase (GOx) on HP-PCN-224(Fe), which can effectively catalyze the
cascade reaction of glucose and ABTS, used as a colorimetric sensor for glucose
detection. Uricase@HP-PCN-224(Fe) was also obtained by immobilizing uricase on
HP-PCN-224(Fe), which can effectively catalyze the cascade
reaction of uric acid and 4-aminophenazone/DCPS, used as a colorimetric
sensor for uric acid (UA) detection. With this strategy, a strong cooperation
of natural enzymes and enzyme mimics is achieved.