Yifei Zhang

Bio: Yifei Zhang is an academic researcher from Columbia University. The author has contributed to research in topics: Lipase & Candida antarctica. The author has an hindex of 18, co-authored 40 publications receiving 1966 citations. Previous affiliations of Yifei Zhang include Beijing University of Chemical Technology & Tsinghua University.

One-Pot Synthesis of Protein-Embedded Metal–Organic Frameworks with Enhanced Biological Activities

Abstract: Protein molecules were directly embedded in metal–organic frameworks (MOFs) by a coprecipitation method. The protein molecules majorly embedded on the surface region of MOFs display high biological activities. As a demonstration of the power of such materials, the resulting Cyt c embedded in ZIF-8 showed a 10-fold increase in peroxidase activity compared to free Cyt c in solution and thus gave convenient, fast, and highly sensitive detection of trace amounts of explosive organic peroxides in solution.

Enhanced Activity of Immobilized or Chemically Modified Enzymes

Abstract: Re-engineering enzymes with high activities in the given environments different from the physiological one has been constantly pursued for application of enzymatic catalysis in industrial biocatalytic processes, pharmaceutical industry, biosensing, etc. Re-engineering enzyme catalysts by chemical approaches, including immobilization and chemical modification, represents a simple but effective route. The unusual phenomenon that immobilized or chemically modified enzymes display higher activities than native enzymes has been observed in both single- and multiple-enzyme systems. Recent achievements in enhancing enzymatic activities in both single-and multiple-enzyme systems by chemical approaches are summarized in this review. We propose that these enhanced enzymatic activities can be attributed to the well-designed specific interactions between immobilization carriers (or chemical modifiers) and enzymes, substrates, or reaction media. In addition to this mechanism, which is applicable for both single- and m...

Proximity does not contribute to activity enhancement in the glucose oxidase-horseradish peroxidase cascade.

Abstract: A proximity effect has been invoked to explain the enhanced activity of enzyme cascades on DNA scaffolds. Using the cascade reaction carried out by glucose oxidase and horseradish peroxidase as a model system, here we study the kinetics of the cascade reaction when the enzymes are free in solution, when they are conjugated to each other and when a competing enzyme is present. No proximity effect is found, which is in agreement with models predicting that the rapidly diffusing hydrogen peroxide intermediate is well mixed. We suggest that the reason for the activity enhancement of enzymes localized by DNA scaffolds is that the pH near the surface of the negatively charged DNA nanostructures is lower than that in the bulk solution, creating a more optimal pH environment for the anchored enzymes. Our findings challenge the notion of a proximity effect and provide new insights into the role of DNA scaffolds.

Toward Rational Design of High-efficiency Enzyme Cascades

Abstract: The construction of an enzyme cascade with enhanced activity is desirable in biocatalysis, synthetic biology and other fields. Although many researchers have found that immobilization of enzyme cascades on scaffolds leads to an enhanced activity, the underlying mechanisms still remain controversial. In this Viewpoint, we describe and discuss the frequently used strategies to achieve activity enhancement. We first reiterate that the proximity does not contribute to the increased overall activity of the sequential nor coenzyme regenerating cascade, and suggest that the reported observed enhancements in the majority of publications were caused by the influence of the scaffolds. Then we discuss the benefits and limitations of other strategies including bridging the enzymes, co-immobilization, compartmentalization. Finally, we highlight that balancing the stoichiometry, improving the individual activity, overlapping the operating temperature and pH maximum are necessary for achieving a high-efficiency enzyme c...

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Abstract: Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Metal–organic frameworks meet metal nanoparticles: synergistic effect for enhanced catalysis

Abstract: Metal–organic frameworks (MOFs), established as a relatively new class of crystalline porous materials with high surface area, structural diversity, and tailorability, attract extensive interest and exhibit a variety of applications, especially in catalysis. Their permanent porosity enables their inherent superiority in confining guest species, particularly small metal nanoparticles (MNPs), for improved catalytic performance and/or the expansion of reaction scope. This is a rapidly developing interdisciplinary research field. In this review, we provide an overview of significant progress in the development of MNP/MOF composites, including various preparation strategies and characterization methods as well as catalytic applications. Special emphasis is placed on synergistic effects between the two components that result in an enhanced performance in heterogeneous catalysis. Finally, the prospects of MNP/MOF composites in catalysis and remaining issues in this field have been indicated.

Biomimetic mineralization of metal-organic frameworks as protective coatings for biomacromolecules.

Abstract: Robust biomacromolecules could be used for a wide range of biotechnological applications. Here the authors report a biomimetic mineralization process, in which biomolecules are encapsulated within metal-organic frameworks, and their stability is subsequently increased without significant bioactivity loss.

One-pot Synthesis of Metal-Organic Frameworks with Encapsulated Target Molecules and Their Applications for Controlled Drug Delivery.

Abstract: Many medical and chemical applications require target molecules to be delivered in a controlled manner at precise locations. Metal-organic frameworks (MOFs) have high porosity, large surface area, and tunable functionality and are promising carriers for such purposes. Current approaches for incorporating target molecules are based on multistep postfunctionalization. Here, we report a novel approach that combines MOF synthesis and molecule encapsulation in a one-pot process. We demonstrate that large drug and dye molecules can be encapsulated in zeolitic imidazolate framework (ZIF) crystals. The molecules are homogeneously distributed within the crystals, and their loadings can be tuned. We show that ZIF-8 crystals loaded with the anticancer drug doxorubicin (DOX) are efficient drug delivery vehicles in cancer therapy using pH-responsive release. Their efficacy on breast cancer cell lines is higher than that of free DOX. Our one-pot process opens new possibilities to construct multifunctional delivery systems for a wide range of applications.

Enzyme–MOF (metal–organic framework) composites

Abstract: The ex vivo application of enzymes in various processes, especially via enzyme immobilization techniques, has been extensively studied in recent years in order to enhance the recyclability of enzymes, to minimize enzyme contamination in the product, and to explore novel horizons for enzymes in biomedical applications. Possessing remarkable amenability in structural design of the frameworks as well as almost unparalelled surface tunability, Metal–Organic Frameworks (MOFs) have been gaining popularity as candidates for enzyme immobilization platforms. Many MOF–enzyme composites have achieved unprecedented results, far outperforming free enzymes in many aspects. This review summarizes recent developments of MOF–enzyme composites with special emphasis on preparative techniques and the synergistic effects of enzymes and MOFs. The applications of MOF–enzyme composites, primarily in transferation, catalysis and sensing, are presented as well. The enhancement of enzymatic activity of the composites over free enzymes in biologically incompatible conditions is emphasized in many cases.