Colloidal-sized zirconium porphyrin metal-organic frameworks with improved peroxidase-mimicking catalytic activity, stability and dispersity

Metal-Organic Framework for the Immobilization of Oxidoreductase Enzymes: Scopes and Perspectives

Oxidoreductases are a wide class of enzymes that can catalyze biological oxidation and reduction reactions. Nowadays, oxidoreductases play a vital part in most bioenergetic metabolic pathways, which have important applications in biodegradation, bioremediation, environmental applications, as well as biosensors. However, free oxidoreductases are not stable and hard to be recycled. In addition, cofactors are needed in most oxidoreductases catalyze reactions, which are so expensive and unstable that it hinders their industrial applications. Enzyme immobilization is a feasible strategy that can overcome these problems. Recently, metal-organic frameworks (MOFs) have shown great potential as support materials for immobilizing enzymes due to their unique properties, such as high surface-area-to-volume ratio, chemical stability, functional designability, and tunable pore size. This review discussed the application of MOFs and their composites as immobilized carriers of oxidoreductase, as well as the application of MOFs as catalysts and immobilized carriers in redox reactions in the perspective of the function of MOFs materials. The paper also focuses on the potential of MOF carrier-based oxidoreductase immobilization for designing an enzyme cascade reaction system.

The construction of Fe-porphyrin nanozymes with peroxidase-like activity for colorimetric detection of glucose

As a type of nanomaterials with enzyme-mimetic catalytic properties, nanozymes have attracted wide concern in biological detection. H₂O₂ was the characteristic product of diverse biological reactions, and the quantitative analysis for H₂O₂ was an important way to detect disease biomarkers, such as acetylcholine, cholesterol, uric acid and glucose. Therefore, there is of great significance for developing a simple and sensitive nanozyme to detect H₂O₂ and disease biomarkers by combining with corresponding enzyme. In this work, Fe-TCPP MOFs were successfully prepared by the coordination between iron ions and porphyrin ligands (TCPP). In addition, the peroxidase (POD) activity of Fe-TCPP was proved, in detail, Fe-TCPP could catalyze H₂O₂ to produce ·OH by Fenton reaction. Herein, glucose oxidase (GOx) was chosen as the model to build cascade reaction by combining Fe-TCPP to detect glucose. The results indicated glucose could be detected by this cascade system selectively and sensitively, and the limit of detection of glucose was achieved to 0.12 μM. Furthermore, a portable hydrogel (Fe-TCPP@GEL) was further established, which encapsulated Fe-TCPP MOFs, GOx and TMB in one system. This functional hydrogel could be applied for colorimetric detection of glucose by coupling with a smartphone easily.

Catalase-integrated metal-organic framework with synergetic catalytic activity for colorimetric sensing

As a platform for enzyme immobilization, metal-organic frameworks (MOFs) can protect enzyme activity from the interference of external adverse environment. Although these strategies have been proven to produce good results, little consideration has been given to the functional similarity of MOFs to the encapsulated enzyme. Here, catalase (CAT) was encapsulated in Fe-BTC with peroxidase-like activity to obtain a stable composite (CAT@Fe-BTC) with synergistic catalytic activity. Depending on the superior selectivity and high catalytic activity of CAT@Fe-BTC, colorimetric sensing for the detection of hydrogen peroxide and phenol was developed. This work demonstrates that the integration of functional MOFs with natural enzyme can be well applied to the construction of efficient catalysts.

Synergetic integration of catalase and Fe3O4 magnetic nanoparticles with metal organic framework for colorimetric detection of phenol

Toxic phenol pollutants pose a great threat to the environment, it is urgent to develop an efficient and recyclable method to monitor phenol. Herein, we reported the synthesis of catalase-Fe₃O₄@ZIF-8 (CAT-Fe₃O₄@ZIF-8) through a novel amino-acid-boosted one-pot embedding strategy that synergically integrated catalase and magnetic Fe₃O₄ nanoparticles with ZIF-8. As expected, CAT-Fe₃O₄@ZIF-8 exhibited enhanced catalytic activity compared with Fe₃O₄@ZIF-8, CAT@ZIF-8 and catalase. Depending on the satisfactory performance of CAT-Fe₃O₄@ZIF-8, a colorimetric detection platform for phenol based on CAT-Fe₃O₄@ZIF-8 was constructed. The corresponding detection limit was as low as 0.7 μM, and a wide linear range of 5-100 μM was obtained. Besides, CAT-Fe₃O₄@ZIF-8-based colorimetric detection platform has been verified to possess high stability and recyclability. The proposed method was proven to have potential practical applications in the field of water treatment, which would advance efficient, recyclable monitoring of water quality.

Ultra-sensitive detection of florfenicol by flow injection chemiluminescence immunoassay based on Nickel/Cobalt bimetallic metal-organic framework nanozymes

The emergence and progress of metal-organic frameworks (MOFs) with high stability, large surface area, and abundant unsaturated active sites, once again promote the development of nanozymes, making nanozymes more advantageous to replace natural enzymes and will increase the applications of chemiluminescence immunoassay. In this study, a flow injection chemiluminescence immunoassay based on Ni/Co metal-organic framework (Ni/Co-MOF) nanozymes was developed, which can quickly and highly sensitively detect florfenicol (FF) in animal-derived food residues. Ni/Co-MOF_0.75 nanospheres can not only form stable immune probes with antibodies but also act as nanozymes to efficiently catalyze H₂O₂ for amplifying the chemiluminescence signal of the luminol-H₂O₂ system. In addition, due to good biocompatibility and large specific surface area, carboxyl-modified resin beads are used as a suitable material for loading more coating antigens. Based on the principle of competitive immunity, FF standard solution will compete with coating antigen loaded on the carboxyl resin beads for the limited binding sites on the FF antibody. Under the best experimental conditions, the detection range of FF is 0.0001-1000 ng mL^-1, and the detection limit (LOD) is 0.033 pg mL^-1 (S/N = 3). Furthermore, this method has been successfully applied to the analysis of actual samples with satisfactory results, which will provide a certain reference for the detection of small molecules in food and environmental analysis.

Explaining chemical clues of metal organic framework-nanozyme nano-/micro-motors in targeted treatment of cancers: benchmarks and challenges

Nowadays, nano-/micro-motors are considered as powerful tools in different areas ranging from cleaning all types of contaminants, to development of Targeted drug delivery systems and diagnostic activities. Therefore, the development and application of nano-/micro-motors based on metal-organic frameworks with nanozyme activity (abbreviated as: MOF-NZs) in biomedical activities have received much interest recently. Therefore, after investigating the catalytic properties and applications of MOF-NZs in the treatment of cancer, this study intends to point out their key role in the production of biocompatible nano-/micro-motors. Since reducing the toxicity of MOF-NZ nano-/micro-motors can pave the way for medical activities, this article examines the methods of making biocompatible nanomotors to address the benefits and drawbacks of the required propellants. In the following, an analysis of the amplified directional motion of MOF-NZ nano-/micro-motors under physiological conditions is presented, which can improve the motor behaviors in the propulsion function, conductivity, targeting, drug release, and possible elimination. Meanwhile, by explaining the use of MOF-NZ nano-/micro-motors in the treatment of cancer through the possible synergy of nanomotors with different therapies, it was revealed that MOF-NZ nano-/micro-motors can be effective in the treatment of cancer. Ultimately, by analyzing the potential challenges of MOF-NZ nano-/micro-motors in the treatment of cancers, we hope to encourage researchers to develop MOF-NZs-based nanomotors, in addition to opening up new ideas to address ongoing problems.