Embedding an enzyme within aMOF as exoskeleton (enzyme@MOF) offers new opportunities to improve the inherent fragile nature of the enzyme,but also to impart novel biofunctionality to the MOF.D espite the remarkable stability achieved for MOF-embedded enzymes,e mbedding patterns and conversion of the enzymatic biofunctionality after entrapment by aM OF have only received limited attention. Herein, we reveal howe mbedding patterns affect the bioactivity of an enzyme encapsulated in ZIF-8. The enzyme@MOF can maintain high activity when the encapsulation process is driven by rapid enzyme-triggered nucleation of ZIF-8. When the encapsulation is driven by slow coprecipitation and the enzymes are not involved in the nucleation of ZIF-8, enzy-me@MOF tends to be inactive owing to unfolding and competing coordination caused by the ligand, 2-methyl imidazole.T hese two embedding patterns can easily be controlled by chemical modification of the amino acids of the enzymes,modulating their biofunctionality.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Crystallization of biomacromolecules-metal-organic frameworks (BMOFs) allows for orderly assemble of symbiotic hybrids with desirable biological and chemical functions in one voxel. The structure-activity relationship of this symbiotic crystal, however, is still blurred. Here, we directly identify the atomic-level structure of BMOFs, using the integrated differential phase contrast-scanning transmission electron microscopy, cryo-electron microscopy and x-ray absorption fine structure techniques. We discover an obvious difference in the nanoarchitecture of BMOFs under different crystallization pathways that was previously not seen. In addition, we find the nanoarchitecture significantly affects the bioactivity of the BMOFs. This work gives an important insight into the structure-activity relationship of BMOFs synthesized in different scenarios, and may act as a guide to engineer next-generation materials with excellent biological and chemical functions.
Mimicking the bioactivity of native enzymes through synthetic chemistry is an efficient means to advance the biocatalysts in a cell-free environment, however, remains long-standing challenges. Herein, we utilize structurally explicit hydrogen-bonded organic frameworks (HOFs) to mimic photo-responsive oxidase, and uncover the important role of pore environments on mediating oxidase-like activity by means of constructing isostructural HOFs. We discover that the HOF pore with suitable geometry can stabilize and spatially organize the catalytic substrate into a favorable catalytic route, as with the function of the native enzyme pocket. Based on the desirable photo-responsive oxidase-like activity, a visual and sensitive HOFs biosensor is established for the detection of phosphatase, an important biomarker of skeletal and hepatobiliary diseases. This work demonstrates that the pore environments significantly influence the nanozymes' activity in addition to the active center.
Enzymes featuring high catalytic efficiency and selectivity have been widely used as the sensing element in analytical chemistry. However, the structural fragility and poor machinability of an enzyme significantly limit its practicability in biosensors. Herein, we develop a robust and sensitive hybrid biosensor by means of co-encapsulating enzymes into a defective metal−organic framework (MOF), followed by a double-crosslinked alginate gelatinization. The defective MOF encapsulation can enhance the stability of enzymes, yet well preserve their biocatalytic function, while the alginate gelatinization allows the MOF biohybrid high stretchability and mechanical strength, which facilitates the integration of a bead-, fiber-, and sheet-like portable biosensor. In this work, the enzymes consisting of glucose oxidase and peroxidase are co-encapsulated into this MOF hydrogel, and it can efficiently convert glucose into a blue-violet product through the biocatalytic cascade of encapsulated enzymes, enabling the colorimetric biosensing of glucose on a miniaturized MOF hydrogel when coupling with a smartphone. Interestingly, this MOF biohybrid hydrogel outputs a stronger sensing signal than the free biohybrid powders, attributed to the catalytic product-accumulated effect of the highly hydrophilic microenvironment of the hydrogel. As a result, this portable biosensor can sensitively and selectively sense glucose with a linear range from 0.05 to 4 mM. Importantly, both the hydrophilic hydrogel and MOF "armor" endow enzymes with high durability, and its sensing activity was well-maintained even after placing the biosensor at room temperature for 30 d. We believe that this MOF biohybrid hydrogel has huge potential for the engineering of next-generation portable biosensors.
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