Fe-Loaded MOF-545(Fe): Peroxidase-Like Activity for Dye Degradation Dyes and High Adsorption for the Removal of Dyes from Wastewater

Recent Progress and Prospect of Metal-Organic Framework-Based Nanozymes in Biomedical Application

A nanozyme is a nanoscale material having enzyme-like properties. It exhibits several superior properties, including low preparation cost, robust catalytic activity, and long-term storage at ambient temperatures. Moreover, high stability enables repetitive use in multiple catalytic reactions. Hence, it is considered a potential replacement for natural enzymes. Enormous research interest in nanozymes in the past two decades has made it imperative to look for better enzyme-mimicking materials for biomedical applications. Given this, research on metal-organic frameworks (MOFs) as a potential nanozyme material has gained momentum. MOFs are advanced hybrid materials made of inorganic metal ions and organic ligands. Their distinct composition, adaptable pore size, structural diversity, and ease in the tunability of physicochemical properties enable MOFs to mimic enzyme-like activities and act as promising nanozyme candidates. This review aims to discuss recent advances in the development of MOF-based nanozymes (MOF-NZs) and highlight their applications in the field of biomedicine. Firstly, different enzyme-mimetic activities exhibited by MOFs are discussed, and insights are given into various strategies to achieve them. Modification and functionalization strategies are deliberated to obtain MOF-NZs with enhanced catalytic activity. Subsequently, applications of MOF-NZs in the biosensing and therapeutics domain are discussed. Finally, the review is concluded by giving insights into the challenges encountered with MOF-NZs and possible directions to overcome them in the future. With this review, we aim to encourage consolidated efforts across enzyme engineering, nanotechnology, materials science, and biomedicine disciplines to inspire exciting innovations in this emerging yet promising field.

Advances in metal-organic frameworks for water remediation applications

Rapid industrialization and agricultural development have resulted in the accumulation of a variety of harmful contaminants in water resources. Thus, various approaches such as adsorption, photocatalytic degradation and methods for sensing water contaminants have been developed to solve the problem of water pollution. Metal-organic frameworks (MOFs) are a class of coordination networks comprising organic-inorganic hybrid porous materials having organic ligands attached to inorganic metal ions/clusters via coordination bonds. MOFs represent an emerging class of materials for application in water remediation owing to their versatile structural and chemical characteristics, such as well-ordered porous structures, large specific surface area, structural diversity, and tunable sites. The present review is focused on recent advances in various MOFs for application in water remediation via the adsorption and photocatalytic degradation of water contaminants. The sensing of water pollutants using MOFs via different approaches, such as luminescence, electrochemical, colorimetric, and surface-enhanced Raman spectroscopic techniques, is also discussed. The high porosity and chemical tunability of MOFs are the main driving forces for their widespread applications, which have huge potential for their commercial use.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Nanozyme-based pollutant sensing and environmental treatment: Trends, challenges, and perspectives

Nanozymes are defined as nanomaterials exhibiting enzyme-like properties, and they possess both catalytic functions and nanomaterial's unique physicochemical characteristics. Due to the excellent stability and improved catalytic activity in comparison to natural enzymes, nanozymes have established a wide base for applications in environmental pollutants monitoring and remediation. Nanozymes have been applied in the detection of heavy metal ions, molecules, and organic compounds, both quantitatively and qualitatively. Additionally, within the natural environment, nanozymes can be employed for the degradation of organic and persistent pollutants such as antibiotics, phenols, and textile dyes. Further, the potential sphere of applications for nanozymes traverses from indoor air purification to anti-biofouling agents, and even they show promise in combatting pathogenic bacteria. However, nanozymes may have inherent toxicity, which can restrict their widespread utility. Thus, it is important to evaluate and monitor the interaction and transformation of nanozymes towards biosphere damage when employed within the natural environment in a cradle-to-grave manner, to assure their utmost safety. In this context, various studies have concluded that the green synthesis of nanozymes can efficiently overcome the toxicity limitations in real life applications, and nanozymes can be well utilized in the sensing and degradation of several toxic pollutants including metal ions, pesticides, and chemical warfare agents. In this seminal review, we have explored the great potential of nanozymes, whilst addressing a range of concerns, which have often been overlooked and currently restrict widespread applications and commercialization of nanozymes.

Substantial increase in adsorption efficiency of local clay-alginate beads toward methylene blue impregnated with SDS

In the current research work, local clay-alginate beads loaded with sodium dodecyl sulfate (SDS) surfactant were prepared for efficient adsorption of methylene blue (MB). FTIR, SEM-EDX, and TGA instruments were used to examine the surface functional groups, morphology, elemental analysis, and thermal stability of beads, respectively. The adsorption efficiency of native clay for MB increases from 124.78 to 247.94 mg/g when loaded in alginate and SDS in beads form. The impacts of adsorbent dosage, initial pH, contact time, initial MB concentration, and temperature were investigated and optimized. The maximum adsorption capacity of beads for MB was 1468.5 mg/g. The process followed a pseudosecond order kinetic and Freundlich adsorption isotherm model. Thermodynamic study confirmed that MB adsorption on beads is endothermic and spontaneous in nature. The beads were recycled and reused for five times. According to the findings, local clay-alginate beads impregnated with SDS proved to be a promising and efficient adsorbent for extracting MB from aqueous solution.

In Situ Generated UiO-66/Cotton Fabric Easily Recyclable for Reactive Dye Adsorption

In view of the environmental pollution caused by the widespread use of reactive dyes in the printing and dyeing industry, the modified cotton fabric was loaded with the extremely stable metal-organic frame (MOF) material UiO-66 for removing reactive dyes from colored wastewater. UiO-66/cotton fabric was prepared by in situ synthesis, and its surface morphology and structure were analyzed by XRD, SEM, BET, and XPS. The adsorption performance of UiO-66/cotton fabric on reactive dyes was investigated by adsorbent dosage, adsorption time and temperature, dye concentration, pH, and so on. The results indicated that the adsorption equilibrium time of UiO-66/cotton fabric on reactive orange 16 was 120 min, and the removal rate was about 98%. The adsorption process belongs to simple molecular layer chemisorption and can be regarded as a spontaneous heat absorption reaction, which was consistent with the proposed secondary kinetic model and Langmuir isothermal adsorption model. In addition, the reactive dyes with a higher molecular weight of each sulfonic acid group are more hydrophobic, and the dyes are more likely to aggregate and deposit on the adsorbent surface by electrostatic attraction, hydrogen bonding, and π-π accumulation. Therefore, this work provides a potential UiO-66/cotton fabric application for the effective adsorption of reactive dyes in textile wastewater.

Controlled Thermal Release of L-Menthol with Cellulose-Acetate-Fiber-Shelled Metal-Organic Framework

Fragrances have been widely used in many customer products to improve the sensory quality and cover flavor defects. The key to the successful application of fragrance is to realize controlled fragrance release, which relies on the use of an appropriate carrier for fragrance. An ideal fragrance carrier helps to achieve the stable storage and controlled release of fragrance. In this work, a novel composite fragrance carrier with MIL-101 (Cr) as the fragrance host and cellulose acetate fiber (CAF) as the protective shell was developed. The encapsulation effect of MIL-101 (Cr) and the protective function of the CAF shell significantly improved the storage stability of L-menthol (LM). Only 5 wt % of LM was lost after 40 days of storage at room temperature. Encapsulated LM could also be effectively released upon heating due to the thermal responsiveness of CAF. In addition, the composite carrier was highly stable with neglectable Cr leaching under different conditions. The results of this work showed that the developed composite carrier could be a promising carrier for the thermally triggered release of fragrance.

Dimensionality reduction boosts the peroxidase-like activity of bimetallic MOFs for enhanced multidrug-resistant bacteria eradication

The antibacterial strategy using cutting-edge metal-organic framework (MOF)-based nanozymes can effectively solve the problem caused by antibiotic resistance to protect human health and the environment; however it has been significantly limited by the complicated modification method and non-ideal catalytic activity. Herein, we report a facile dimensionality-reduction strategy to improve the catalytic activity of MOF-based nanozymes. By reducing the dimensionality of two-dimensional Co-TCPP(Fe) (Co-Fe NSs) to zero-dimensional Co-TCPP(Fe) (Co-Fe NDs), the peroxidase-like activity of the prepared bimetallic Co-Fe NDs was almost tripled. Consequently, the bimetallic Co-Fe NDs can highly efficiently catalyze the lower-concentration H₂O₂ into reactive oxygen species (ROS), resulting in a favorable antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA). Meanwhile, Co-Fe NDs can effectively promote wound healing and water environment disinfection with good biocompatibility. This work reveals the potential of a zero-dimensional bimetallic MOF-based nanozyme in resisting drug-resistant bacteria and holds great promise for future clinical and environmental applications.

Metal organic framework-based antibacterial agents and their underlying mechanisms

Bacteria, as the most abundant living organisms, have always been a threat to human life until the development of antibiotics. However, with the wide use of antibiotics over a long time, bacteria have gradually gained tolerance to antibiotics, further aggravating threat to human beings and environmental safety significantly. In recent decades, new bacteria-killing methods based on metal ions, hyperthermia, free radicals, physical pricks, and the coordination of several multi-mechanisms have attracted increasing attention. Consequently, multiple types of new antibacterial agents have been developed. Among them, metal organic frameworks (MOFs) appear to play an increasingly important role. The unique characteristics of MOFs make them suitable multiple-functional platforms. By selecting the appropriate metastable coordination bonds, MOFs can act as reservoirs and release antibacterial metal ions or organic linkers; by constructing a porous structure, MOFs can act as carriers for multiple types of agents and achieve slow and sustained release; and by designing their composition and the pore structure precisely, MOFs can be endowed with properties to produce heat and free radicals under stimulation. Importantly, in combination with other materials, MOFs can act as a platform to kill bacteria effectively through the synergistic effect of multiple types of mechanisms. In this review, we focus on the recent development of MOF-based antibacterial agents, which are classified according to their antibacterial mechanisms.

Biotechnological and Technical Challenges Related to Cultured Meat Production

The constant growth of the population has pushed researchers to find novel protein sources. A possible solution to this problem has been found in cellular agriculture, specifically in the production of cultured meat. In the following review, the key steps for the production of in vitro meat are identified, as well as the most important challenges. The main biological and technical approaches are taken into account and discussed, such as the choice of animal, animal-free alternatives to fetal bovine serum (FBS), cell biomaterial interactions, and the implementation of scalable and sustainable biofabrication and culturing systems. In the light of the findings, as promising as cultured meat production is, most of the discussed challenges are in an initial stage. Hence, research must overcome these challenges to ensure efficient large-scale production.

Astragalus polysaccharide: a review of its immunomodulatory effect

The Astragalus polysaccharide is an important bioactive component derived from the dry root of Astragalus membranaceus. This review aims to provide a comprehensive overview of the research progress on the immunomodulatory effect of Astragalus polysaccharide and provide valuable reference information. We review the immunomodulatory effect of Astragalus polysaccharide on central and peripheral immune organs, including bone marrow, thymus, lymph nodes, spleen, and mucosal tissues. Furthermore, the immunomodulatory effect of Astragalus polysaccharide on a variety of immune cells is summarized. Studies have shown that Astragalus polysaccharide can promote the activities of macrophages, natural killer cells, dendritic cells, T lymphocytes, B lymphocytes and microglia and induce the expression of a variety of cytokines and chemokines. The immunomodulatory effect of Astragalus polysaccharide makes it promising for the treatment of many diseases, including cancer, infection, type 1 diabetes, asthma, and autoimmune disease. Among them, the anticancer effect is the most prominent. In short, Astragalus polysaccharide is a valuable immunomodulatory medicine, but further high-quality studies are warranted to corroborate its clinical efficacy.

Multi-activity cobalt ferrite/MXene nanoenzymes for drug-free phototherapy in bacterial infection treatment

Drug-free antibacterial strategies are of great significance for pathogenic bacterial infection treatment in clinical practice. Phototherapy with antibacterial function plays a vital role in mainstream germicidal research. However, phototherapy could lead to residual heat and excess reactive oxygen species (ROS), which are the main side-effects during antibacterial treatment. Unique CoFe2O4/MXene (CM) nanoenzymes, which were fabricated with electrostatic interactions, have been designed to conquer those challenges caused by side-effects of phototherapy in our research. The CM nanoenzymes possess many promising properties including photothermal and photodynamic induced phototherapy and mimic peroxidase (POD), glutathione oxidase (GSHOx), and catalase (CAT). Upon treatment with near-infrared (NIR) light, CM nanoenzymes can create a local high-temperature circumstance as well as raise bacterial membrane permeability. Furthermore, the photodynamic process and multi-enzyme-mimicking activities of CM enzymes boost the interbacterial ROS level. Herein, bacteria can hardly survive in synergistic phototherapy and multi-enzyme-mimicking catalytic therapy in vitro and in vivo. Meanwhile, the CM nanoenzymes exhibit excellent biocompatibility in vitro and in vivo. Overall, this research establishes a strong foundation for effectively employing nanoenzymes, leading to a new way to cure bacterial infections.

An Integrative Approach to Study Bacterial Enzymatic Degradation of Toxic Dyes

Synthetic dyes pose a large threat to the environment and consequently to human health. Various dyes are used in textile, cosmetics, and pharmaceutical industries, and are released into the environment without any treatment, thus adversely affecting both the environment and neighboring human populations. Several existing physical and chemical methods for dye degradation are effective but have many drawbacks. Biological methods over the years have gained importance in the decolorization and degradation of dye and have also overcome the disadvantages of physiochemical methods. Furthermore, biological methods are eco-friendly and lead to complete decolorization. The mechanism of decolorization and degradation by several bacterial enzymes are discussed in detail. For the identification of ecologically sustainable strains and their application at the field level, we have focused on bioaugmentation aspects. Furthermore, in silico studies such as molecular docking of bacterial enzymes with dyes can give a new insight into biological studies and provide an easy way to understand the interaction at the molecular level. This review mainly focuses on an integrative approach and its importance for the effective treatment and decolorization of dyes.

A two-dimensional thin Co-MOF nanosheet as a nanozyme with high oxidase-like activity for GSH detection

A two-dimensional thin Co-MOF (ZIF-67) nanosheet with high oxidase-like activity was applied for sensitive visual GSH detection.

Multi-functional metal-organic frameworks for detection and removal of water pollutions

Water pollutions have caused serious threats to the aquatic environment and human health, it is of great significance to monitor and control their contents in water. Compared with the traditional...

Synthesis of a 2D copper(II)-carboxylate framework having ultrafast adsorption of organic dyes

Two-dimensional (2D) coordination polymers are very interesting materials for their attractive applications. A novel 2D metal-organic framework (MOF) was derived from copper(II) and amino benzoic acid under both room temperature and solvothermal reaction conditions using different solvents. From both of the synthesis methods, an identical MOF was crystalized with monoclinic crystal system having P2₁/c space group. Hirshfeld surface analysis is carried out to explore the non-covalent interactions obtained from single crystal XRD investigation in terms of percentage contribution of each interatomic contact involved in packing of molecules into MOF structure. The microstructure analysis and surface morphology studies revealed the 2D layered regular pattern of rhombus disks of ~5 μm thickness throng together via clustering of these rhombic shaped flakes as flowers (ranging 50-100 μm in size) having uniform elemental composition. This 2D MOF efficiently adsorbed organic dyes (methylene blue, methyl orange, and methyl red) from their aqueous solutions. The 2D copper-carboxylate framework (1.2 g/L) exhibited high adsorption rates for organic dyes (0.15-0.19 mM), and >90% of these dyes could be captured as soon as they are exposed to MOF suspension (1 min) in each case. The dye removal efficiency is credited to synergy among structure, ionic strength, shapes and dimensions of dyes with respect to MOF structure. The microstructure of MOF along with electronic interactions like electrostatic, hydrogen bonding, π-π interactions and coordination to open metal sites, might contribute to the ultrafast dye adsorption process by MOF. The adsorption phenomenon is spontaneous and followed the pseudo-second order kinetic mechanism. DFT calculations revealed important electronic parameters of the dyes and model MOF systems, and novel insights with respect to possible dye-MOF interactions. The MOF remained quite stable during the dye adsorption and was regenerated easily for the successful subsequent use.

Blood-Brain Barrier Dysfunction in the Pathogenesis of Major Depressive Disorder

Major depression represents a complex and prevalent psychological disease that is characterized by persistent depressed mood, impaired cognitive function and complicated pathophysiological and neuroendocrine alterations. Despite the multifactorial etiology of depression, one of the most recent factors to be identified as playing a critical role in the development of depression is blood-brain barrier (BBB) disruption. The occurrence of BBB integrity disruption contributes to the disturbance of brain homeostasis and leads to complications of neurological diseases, such as stroke, chronic neurodegenerative disorders, neuroinflammatory disorders. Recently, BBB associated tight junction disruption has been shown to implicate in the pathophysiology of depression and contribute to increased susceptibility to depression. However, the underlying mechanisms and importance of BBB damage in depression remains largely unknown. This review highlights how BBB disruption regulates the depression process and the possible molecular mechanisms involved in development of depression-induced BBB dysfunction. Moreover, insight on promising therapeutic targets for treatment of depression with associated BBB dysfunctions are also discussed.

Recent Improvement Strategies on Metal-Organic Frameworks as Adsorbent, Catalyst, and Membrane for Wastewater Treatment

The accumulation of pollutants in water is dangerous for the environment and human lives. Some of them are considered as persistent organic pollutants (POPs) that cannot be eliminated from wastewater effluent. Thus, many researchers have devoted their efforts to improving the existing technology or providing an alternative strategy to solve this environmental problem. One of the attractive materials for this purpose are metal-organic frameworks (MOFs) due to their superior high surface area, high porosity, and the tunable features of their structures and function. This review provides an up-to-date and comprehensive description of MOFs and their crucial role as adsorbent, catalyst, and membrane in wastewater treatment. This study also highlighted several strategies to improve their capability to remove pollutants from water effluent.

Metal Organic Frameworks Derived Fe-N-C Nanostructures as High-Performance Electrodes for Sodium Ion Batteries and Electromagnetic Interference (EMI) Shielding

Metal organic framework (MOF)-derived carbon nanostructures (MDC) synthesized by either calcinations or carbonization or pyrolysis are emerging as attractive materials for a wide range of applications like batteries, super-capacitors, sensors, water treatment, etc. But the process of transformation of MOFs into MDCs is time-consuming, with reactions requiring inert atmospheres and reaction time typically running into hours. In this manuscript, we report the transformation of 1,4-diazabicyclo[2.2.2]octane, (DABCO)-based MOFs into iron nitride nanoparticles embedded in nitrogen-doped carbon nanotubes by simple, fast and facile microwave pyrolysis. By using graphene oxide and carbon fiber as microwave susceptible surfaces, three-dimensional nitrogen-doped carbon nanotubes vertically grown on reduced graphene oxide (MDNCNT@rGO) and carbon fibers (MDCNT@CF), respectively, were obtained, whose utility as anode material in sodium-ion batteries (MDNCNT@rGO) and for EMI (electromagnetic interference) shielding material (MDCNT@CF) is reported.

Optimization of theoretical maximal quantity of cells to immobilize on solid supports in the rational design of immobilized derivatives strategy

Current worldwide challenges are to increase the food production and decrease the environmental contamination by industrial emissions. For this, bacteria can produce plant growth promoter phytohormones and mediate the bioremediation of sewage by heavy metals removal. We developed a Rational Design of Immobilized Derivatives (RDID) strategy, applicable for protein, spore and cell immobilization and implemented in the RDID_1.0 software. In this work, we propose new algorithms to optimize the theoretical maximal quantity of cells to immobilize (tMQ_Cell) on solid supports, implemented in the RDID_Cell software. The main modifications to the preexisting algorithms are related to the sphere packing theory and exclusive immobilization on the support surface. We experimentally validated the new tMQ_Cell parameter by electrostatic immobilization of ten microbial strains on AMBERJET^® 4200 Cl^- porous solid support. All predicted tMQ_Cell match the practical maximal quantity of cells to immobilize with a 10% confidence. The values predicted by the RDID_Cell software are more accurate than the values predicted by the RDID_1.0 software. 3-indolacetic acid (IAA) production by one bacterial immobilized derivative was higher (~ 2.6 μg IAA-like indoles/10⁸ cells) than that of the cell suspension (1.5 μg IAA-like indoles/10⁸ cells), and higher than the tryptophan amount added as indole precursor. Another bacterial immobilized derivative was more active (22 μg Cr(III)/10⁸ cells) than the resuspended cells (14.5 μg Cr(III)/10⁸ cells) in bioconversion of Cr(VI) to Cr(III). Optimized RDID strategy can be used to synthesize bacterial immobilized derivatives with useful biotechnological applications.

Mesoporous Mn-Doped Fe Nanoparticle-Modified Reduced Graphene Oxide for Ethyl Violet Elimination: Modeling and Optimization Using Artificial Intelligence

Mesoporous Mn-doped Fe nanoparticle-modified reduced graphene oxide (Mn-doped Fe/rGO) was prepared through a one-step co-precipitation method, which was then used to eliminate ethyl violet (EV) in wastewater. The prepared Mn-doped Fe/rGO was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, N2-sorption, small angle X-ray diffraction and superconducting quantum interference device. The Brunauer–Emmett–Teller specific surface area of Mn-doped Fe/rGO composites was 104.088 m2/g. The EV elimination by Mn-doped Fe/rGO was modeled and optimized by artificial intelligence (AI) models (i.e., radial basis function network, random forest, artificial neural network genetic algorithm (ANN-GA) and particle swarm optimization). Among these AI models, ANN-GA is considered as the best model for predicting the removal efficiency of EV by Mn-doped Fe/rGO. The evaluation of variables shows that dosage gives the maximum importance to Mn-doped Fe/rGO removal of EV. The experimental data were fitted to kinetics and adsorption isotherm models. The results indicated that the process of EV removal by Mn-doped Fe/rGO obeyed the pseudo-second-order kinetics model and Langmuir isotherm, and the maximum adsorption capacity was 1000.00 mg/g. This study provides a possibility for synthesis of Mn-doped Fe/rGO by co-precipitation as an excellent material for EV removal from the aqueous phase.