Magnetic metal–organic frameworks as scaffolds for spatial co-location and positional assembly of multi-enzyme systems enabling enhanced cascade biocatalysis

Abstract

Magnetic multi-enzyme nanosystems have been prepared via co-precipitation of enzymes and metalorganic framework HKUST-1 precursors in the presence of magnetic Fe 3 O 4 nanoparticles. The spatial co-localization of two enzymes was achieved using a layer-by-layer positional assembly strategy.Glucose oxidase (GOx) and horseradish peroxidase (HRP) were used as the model enzymes for cascade biocatalysis. By controlling the spatial positions of enzymes, three bienzyme nanosystems GOx@HRP@HKUST-1@Fe 3 O 4 , GOx-HRP@HKUST-1@Fe 3 O 4 and HRP@GOx@HKUST-1@Fe 3 O 4 were prepared in which GOx and HRP containing layers were in close proximity, either encapsulated in the HKUST-1 inner layer, or immobilized on the HKUST-1 outer shell, or randomly distributed in the two MOF layers. Their properties were characterized by transmission electron microscopy, energydispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and zeta potential measurements. The highest activity was observed at pH ¼ 6 and a temperature of 20 C. Thanks to the favorable positioning of enzymes, the GOx@HRP@HKUST-

Development of a Four-Enzyme Magnetic Nanobiocatalyst for Multi-Step Cascade Reactions

“…Specifically, we varied the mass ratio of CelDZ1, bgl, GOx and HRP from 1:1:1:1 to 1:1:1:3, respectively. It was indicated that the use of excess HRP concentration during the immobilization process, enhanced the final step of the studied cascade process, a result that is in accordance with other studies that reported that the increase in the initial amount of HRP is essential in the development of robust bi-enzymatic systems comprising of GOx and HRP [28,29]. Glutaraldehyde, acting as a bifunctional cross-linker, reacts with the amino groups of both the enzymes and the MNPs, directly affecting enzyme loading, activity recovery and operational stability of the prepared nanobiocatalyst [30].…”

Multi‐enzyme Cascade Reactions in Metal‐organic Frameworks

“…[34,35,48] Moreover, by selecting the appropriate MOF materials for immobilization, multi-enzyme cascade reactions can be accurately controlled by the spatially positioned and orientated enzymes in nanoscale-precision. [39,49,50] In addition, to endow multi-enzyme catalysis with the smart and stimuli-responsive property, compartmentalization of enzymes sometimes is required to provide a separated space for different enzymes, which is helpful to regulate enzymes and enhance their whole catalytic performance. [41,55,56] More excitingly, with the merits of compartmentalization strategy and communication capability of MOFs, some chemically incompatible enzymes (e. g. protease and glucose oxidase) can be coupled together to function cooperatively for chemical synthesis.…”

“…Notably, with satisfying advantages, multi-enzyme cascade reactions in MOFs have been exploited in several field. For example, with multi-enzyme encapsulated in MOFs, the multi-enzyme@MOF systems highlight new possibilities in biosensors, which enable a series of biomarkers detection such as glucose, [34,35,42,49,53] cholesterol, [37] uric acid, [42] lactose, [53] and so on. Furthermore, due to the high enzyme loading capacity, biodegradability, and high biocompatibility in vitro and in vivo, multi-enzyme@MOF systems have also shown considerable promise in catalytic nanomedicine applications, such as glucose oxidase (GOx) and horseradish peroxidase (HRP) or chloroperoxidase (CPO) co-encapsulated in MOFs induced high toxic reactive oxygen species (ROS) generation for tumor cell therapy, [44,45] and GOx and catalase co-immobilized within MOFs enabled smart drug delivery with negligible cytotoxicity.…”

Recent Advances in Preparation and Applications of Magnetic Framework Composites

“…The seed crystal method has also been successfully applied to the preparation of Fe 3 O 4 @HKUST‐1 . Fe 3 O 4 @Cu 2+ @H 3 BTC was obtained by dispersing the citric acid‐coated Fe 3 O 4 nanoparticles into copper(II) acetate and H 3 BTC respectively, and then under hydrothermal conditions as a seed crystal to prepared Fe 3 O 4 @HKUST‐1.…”