DNA-directed enzyme immobilization on Fe3O4 modified with nitrogen-doped graphene quantum dots as a highly efficient and stable multi-catalyst system
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The exploration of new tactics for manufacturing artificial immobilized multi-enzyme systems based on enzyme cascades has recently attracted considerable interest because of the urgent need for multi-enzyme catalysts and the high cost of free enzymes. Because of the inevitable limitations of native enzymes such as instability and storage issues, the development of nanozyme–enzyme cascades is needed. A versatile strategy was developed for fabricating an efficient multi-catalyst system by immobilizing glucose oxidase (GOx) on ferriferous oxide nanocomposites functionalized with nitrogen-doped graphene quantum dots (Fe3O4@N-GQDs) through DNA-directed immobilization. The Fe3O4@N-GQDs acted as a carrier for the natural enzyme and showed high peroxidase activity which enabled an enzyme cascade that included GOx to be set up. This multi-catalyst system showed great catalytic activity, reversibility and operational stability. The surfaces of GOx-targeted magnetic nanoparticles were regenerated by mild dehybridization of DNA. The Michaelis constant (Km) and maximum initial velocity (Vmax) of the multi-catalyst system were 1.069 mM and 11.2 × 10−8 M s−1, respectively, which are considerably better than the corresponding values for adsorbed and free bienzyme combinations. The increased bioactivity of the multi-catalyst system is ascribed to the satisfactory peroxidase-like activity of Fe3O4@N-GQDs, the enzyme–promoting effect of the QDs and enhancement by DNA-directed immobilization. Because of the diverse range of possible nanozyme–enzyme combinations and high efficiency of this approach, this work provides a novel pathway for the manufacturing of synthetic enzyme catalyst systems, which have great potential in the field of biotechnology.
This work was supported by the National Natural Science Foundation of China (Grant No. 21675008) and the National Key Research and Development Program of China: Studies and applications of NQI technologies of graphene and related materials (No. 2016YFF0204303).
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Conflict of interest
The authors declare no competing financial interest.
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