User-Tailored Metal-Organic Frameworks as Supports for Carbonic Anhydrase

Investigation of biosensing properties in magnetron sputtered metallized UV-curable polymer microneedle electrodes

Direct management and assessment of metal film properties applied to polymer microneedle (MN) biosensors remains difficult due to constraints inherent to their morphology. By simplifying the three-dimensional structure of MNs and adjusting the deposition time, different thicknesses of Au films were deposited on the UV-cured polymer planar and MN substrates. Several properties relevant to the biosensing of the Au films grown on the polymer surfaces were investigated. The results demonstrate the successful deposition of pure and stable Au nanoparticles onto the surface of UV-curable polymer materials. Initially, Au islands formed within the first minute of deposition; however, as the sputtering time extended, these islands transformed into Au nanoparticle films and disappeared. The hydrophilicity of the surface remains unchanged, while the surface resistance of the thin film decreases with increasing thickness, and the adhesion to the substrate decreases as the thickness increases. In short, a sputtering time of 5-6 min results in Au films with a thickness of 100-200 nm, which exhibit exceptional comprehensive biosensing performance. Additionally, MNs made of Au/UV-curable polymers and produced using magnetron sputtering maintain their original shape, enhance their mechanical characteristics, and gain new functionalities. The Au/UV-curable polymer MNs exhibited remarkable electrode performance despite being soaked in a 37 °C PBS solution for 14 days. These discoveries have important implications in terms of decreasing the dependence on valuable metals in MN biosensors, lowering production expenses, and providing guidance for the choice and design of materials for UV-curable polymer MN metallization films.

Carbonic anhydrase as a tool to mitigate global warming

The global average temperature breaks the record every year, and this unprecedented speed at which it is unfolding is causing serious climate change which in turn impacts the lives of humans and other living organisms. Thus, it is imperative to take immediate action to limit global warming. Increased CO2 emission from the industrial sector that relies on fossil fuels is the major culprit. Mitigating global warming is an uphill battle that involves an integration of technologies such as switching to renewable energy, increasing the carbon sink capacity, and implementing carbon capture and sequestration (CCS) on major sources of CO2 emissions. Among all these methods, CCS is globally accepted as a potential technology to address this climate change. CCS using carbonic anhydrase (CA) is gaining momentum due to its advantages over other conventional CCS technologies. CA is a metalloenzyme that catalyses a fundamental reaction for life, i.e. the interconversion of bicarbonate and protons from carbon dioxide and water. The practical application of CA requires stable CAs operating under harsh operational conditions. CAs from extremophilic microbes are the potential candidates for the sequestration of CO2 and conversion into useful by-products. The soluble free form of CA is expensive, unstable, and non-reusable in an industrial setup. Immobilization of CA on various support materials can provide a better alternative for application in the sequestration of CO2. The present review provides insight into several types of CAs, their distinctive characteristics, sources, and recent developments in CA immobilization strategies for application in CO2 sequestration.

Carbonic Anhydrase-Embedded ZIF-8 Electrospun PVA Fibers as an Excellent Biocatalyst Candidate

There is a growing concern that the increasing concentration of CO₂ in the atmosphere contributes to a potential negative impact on global climate change. To deal with this problem, developing a set of innovative, practical technologies is essential. In the present study, maximizing the CO₂ utilization and precipitation as CaCO₃ was evaluated. In this manner, bovine carbonic anhydrase (BCA) was embedded into the microporous zeolite imidazolate framework, ZIF-8, via physical absorption and encapsulation. Running as crystal seeds, these nanocomposites (enzyme-embedded MOFs) were in situ grown on the cross-linked electrospun polyvinyl alcohol (CPVA). The prepared composites displayed much higher stability against denaturants, high temperatures, and acidic media than free BCA, and BCA immobilized into or on ZIF-8. During 37 days of storage period study, BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA maintained more than 99 and 75% of their initial activity, respectively. The composition of BCA@ZIF-8 and BCA/ZIF-8 with CPVA improved stability for consecutive usage in recovery reactions, recycling easiness, and greater control over the catalytic process. The amounts of calcium carbonate obtained by one mg each of fresh BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA were 55.45 and 49.15 mg, respectively. The precipitated calcium carbonate by BCA@ZIF-8/CPVA reached 64.8% of the initial run, while this amount was 43.6% for BCA/ZIF-8/CPVA after eight cycles. These results indicated that the BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA fibers could be efficiently applied to CO₂ sequestration.

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.

Strategies to improve the mass transfer in the CO2 capture process using immobilized carbonic anhydrase

High carbon dioxide (CO₂) concentration in the atmosphere urgently requires eco-friendly mitigation strategies. Carbonic anhydrase (CA) is a high-quality enzyme protein, available from a wide range of sources, which has an extremely high catalytic efficiency for the hydration of CO₂ compared with other catalytic CO₂ conversion systems. While free CA is costly and weakly stable, CA immobilization can significantly improve its stability and allow enzyme recycling. However, gaseous CO₂ is significantly different from traditional liquid substrates. Additionally, due to the presence of enzyme carriers, there is limited mass transfer between CO₂ and the active center of immobilized CA. Most of the available reviews provide an overview of the improvement in catalytic activity and stability of CA by different immobilization methods and substrates. However, they do not address the limited mass transfer between CO₂ and the active center of immobilized CA. Therefore, by focusing on the mass transfer process, this review presents CA immobilization strategies that are more efficient and of greater environmental tolerance by categorizing the methods of enhancing the mass transfer process at each stage of the enzymatic CO₂ capture reaction. Such improvements in this green and environmentally friendly biological carbon capture process can increase its efficiency for industrial applications.

Assessment of Enzyme Functionality at Metal-Organic Framework Interfaces Developed through Molecular Simulations

The catalytic efficiency and unrivaled selectivity with which enzymes convert substrates to products have been tapped for widespread chemical transformations within biomedical technology, biofuel production, gas sensing, and the upgrading of commodity chemicals, just to name a few. However, the feasibility of enzymes implementation is challenged by the lack of reusability and loss of native catalytic activity due to the irreversible biocatalyst denaturation at high temperatures and in the presence of industrial solvents. Enzyme immobilization, a prerequisite for enzyme reusability, offers controllable strategies for increased functional viability of the biocatalyst in a synthetic environment. Herein we used molecular dynamics (MD) simulations and probed the noncovalent interactions between model enzymes of technological interest, i.e., carbonic anhydrase (CA) and myeloperoxidase (MPO), with selected metal-organic frameworks (MOFs; MIL-160 and ZIF-8) of proven industrial implementation. We found that the CA and MPO can bind to MIL-160 at optimal binding energies of 201 and 501 kJ mol^-1, respectively, that are strongly influenced by the increased incidence of hydrogen bonding between enzymes and the frameworks. The free energy of binding of enzymes to ZIF-8, on the other hand, was found to be less strongly influenced by hydrogen bonding networks relative to the occurrence of hydrophobic-hydrophobic interactions that yielded 106 kJ mol^-1 for CA and 201 kJ mol^-1 for MPO.

Microbial carbonic anhydrase mediated carbon capture, sequestration & utilization: A sustainable approach to delivering bio-renewables

In the recent scenario, anthropogenic interventions have alarmingly disrupted climatic conditions. The persistent change in the climate necessitates carbon neutrality. Efficient ways of carbon capture and sequestration could be employed for sustainable product generation. Carbonic anhydrase (CA) is an enzyme that reversibly catalyzes the conversion of carbon dioxide to bicarbonate ions, further utilized by cells for metabolic processes. Hence, utilizing CA from microbial sources for carbon sequestration and the corresponding delivery of bio-renewables could be the eco-friendly approach. Consequently, the microbial CA and amine-based carbon capture chemicals are synergistically applied to enhance carbon capture efficiency and eventual utilization. This review comprehends recent developments coupled with engineering techniques, especially in microbial CA, to create integrated systems for CO₂ sequestration. It envisages developing sustainable approaches towards mitigating environmental CO₂ from industries and fossil fuels to generate bio-renewables and other value-added chemicals.

Enzyme-immobilized metal-organic frameworks: From preparation to application

As a class of widely used biocatalysts, enzymes possess advantages including high catalytic efficiency, strong specificity and mild reaction condition. However, most free enzymes have high requirements on the reaction environment and are easy to deactivate. Immobilization of enzymes on nanomaterial-based substrates is a good way to solve this problem. Metal-organic framework (MOFs), with ultra-high specific surface area and adjustable porosity, can provide a large space to carry enzymes. And the tightly surrounded protective layer of MOFs can stabilize the enzyme structure to a great extent. In addition, the unique porous network structure enables selective mass transfer of substrates and facilitates catalytic processes. Therefore, these enzyme-immobilized MOFs have been widely used in various research fields, such as molecule/biomolecule sensing and imaging, disease treatment, energy and environment protection. In this review, the preparation strategies and applications of enzymes-immobilized MOFs are illustrated and the prospects and current challenges are discussed.

Confining enzymes in porous organic frameworks: from synthetic strategy and characterization to healthcare applications

Enzymes are a class of natural catalysts with high efficiency, specificity, and selectivity unmatched by their synthetic counterparts and dictate a myriad of reactions that constitute various cascades in living cells. The development of suitable supports is significant for the immobilization of structurally flexible enzymes, enabling biomimetic transformation in the extracellular environment. Accordingly, porous organic frameworks, including metal organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), have emerged as ideal supports for the immobilization of enzymes because of their structural features including ultrahigh surface area, tailorable porosity, and versatile framework compositions. Specially, organic framework-encased enzymes have shown significant enhancement in stability and reusability, and their tailorable pore opening provides a gatekeeper-like effect for guest sieving, which is beneficial for mimicking intracellular biocatalysis processes. This immobilization technique brings new insight into the development of next-generation enzyme materials and shows huge potential in healthcare applications, such as biomarker diagnosis, biostorage, and cancer and antibacterial therapies. In this review, we describe the state-of-the-art strategies for the structural immobilization of enzymes using the well-explored MOFs and burgeoning COFs and HOFs as scaffolds, with special emphasis on how these porous framework-confined technologies can provide a favorable microenvironment for mimicking natural biocatalysis. Subsequently, advanced characterization techniques for enzyme conformation, the effect of the confined microenvironment on the activity of enzymes, and the emerging healthcare applications will be surveyed.

Diverse Applications of Biomass-Derived 5-Hydroxymethylfurfural and Derivatives as Renewable Starting Materials

This Review summarizes recent efforts to capitalize on 5-hydroxymethylfurfural (HMF) and related furans as emerging building blocks for the synthesis of fine chemicals and materials, with a focus on advanced applications within medicinal and polymer chemistry, as well as nanomaterials. As with all chemical industries, these fields have historically relied heavily on petroleum-derived starting materials, an unsustainable and polluting feedstock. Encouragingly, the emergent chemical versatility of biomass-derived furans has been shown to facilitate derivatization towards valuable targets. Continued work on the synthetic manipulation of HMF, and related derivatives, for access to a wide range of target compounds and materials is crucial for further development. Increasingly, biomass-derived furans are being utilized for a wide range of chemical applications, the continuation of which is paramount to accelerate the paradigm shift towards a sustainable chemical industry.

Metal-based micro-composite of L-arabinose isomerase and L-ribose isomerase for the sustainable synthesis of L-ribose and D-talose

The biocatalysts are broadly explored in the biological transformation processes. The enzyme cascade catalysis involves various catalytic activities in a sequential process to produce the desired product including the formation of reaction intermediates. Enzyme immobilization is a method in which enzymes are confined within a support or matrix either physically or chemically to enhance their relative stability and catalytic activity in the enzyme cascade catalysis. In view of this, L-arabinose isomerase (L-AI) and L-ribose isomerase (L-RI) were immobilized on zeolite based metal framework as a micro-composite construct (DEMC@L-AI+L-RI) using linker, and metal ions. Such immobilization could be of great significance and provide several advantages like mesoporous surface for enzyme adsorption, desirable functionality in the production of products in enzyme cascade reaction, high storage stability and enhanced recyclability. The developed DEMC@L-AI+L-RI was characterized using SEM, FTIR, CLSM and TGA. The immobilization yield was 32% and loading of enzyme was 22% on the surface of micro-composite. The DEMC@L-AI+L-RI showed relatively stable catalytic activity at pH 5-6 and temperature 40 °C. The catalytic efficiency (k_cat/K_m) of both the enzymes was increased by 1.5-fold after immobilization. With the immobilized biocatalyst, bioconversion of L-arabinose to L-ribose was 22.6% and D-galactose to D-talose was 15.2%. The reusability of developed biocatalyst for more than six cycles was observed for more than 50% yield of the sugars. The conversion of biomass sugars from beetroot and onion waste residues was 20% and 14% to produce ribose and talose, respectively.

Immobilization of carbonic anhydrase for CO2 capture and utilization

Carbonic anhydrase (CA) is an excellent candidate for novel biocatalytic processes based on the capture and utilization of CO₂. The setup of efficient methods for enzyme immobilization makes CA utilization in continuous bioreactors increasingly attractive and opens up new opportunities for the industrial use of CA. The development of efficient processes for CO₂ capture and utilization (CCU) is one of the most challenging targets of modern chemical reaction engineering. In the general frame of CCU processes, the interest in the utilization of immobilized CA as a biocatalyst for augmentation of CO₂ reactive absorption has grown consistently over the last decade. The present mini-review surveys and discusses key methodologies for CA immobilization aimed at the development of heterogeneous biocatalysts for CCU. Advantages and drawbacks of covalent attachment on fine granular solids, immobilization as cross-linked enzyme aggregates, and "in vivo" immobilization methods are presented. In particular, criteria for optimal selection of CA-biocatalyst and design of CO₂ absorption units are presented and discussed to highlight the most effective solutions. Perspectives on biocatalytic CCU processes that can include the use of CA in an enzymatic reactive CO₂ absorption step are eventually presented with a special focus on two examples of CO₂ fixation pathways: hybrid enzyme-microalgae process and enzyme cascade for the production of carboxylic acids. KEY POINTS: • Covalent immobilization techniques applied to CA are effective for CO₂ ERA. • Biocatalyst type and morphology must be selected considering CO₂ ERA conditions. • Immobilized CA can offer novel routes to CO₂ capture and direct utilization.

Emerging 3D Printing Strategies for Enzyme Immobilization: Materials, Methods, and Applications

As the strategies of enzyme immobilization possess attractive advantages that contribute to realizing recovery or reuse of enzymes and improving their stability, they have become one of the most desirable techniques in industrial catalysis, biosensing, and biomedicine. Among them, 3D printing is the emerging and most potential enzyme immobilization strategy. The main advantages of 3D printing strategies for enzyme immobilization are that they can directly produce complex channel structures at low cost, and the printed scaffolds with immobilized enzymes can be completely modified just by changing the original design graphics. In this review, a comprehensive set of developments in the fields of 3D printing techniques, materials, and strategies for enzyme immobilization and the potential applications in industry and biomedicine are summarized. In addition, we put forward some challenges and possible solutions for the development of this field and some possible development directions in the future.

Metal-Organic Frameworks as a Versatile Materials Platform for Unlocking New Potentials in Biocatalysis

Biocatalysts immobilization with nanomaterials has promoted the development of biocatalysis significantly and made it an indispensable part of catalysis industries nowadays. Metal-organic frameworks (MOFs), constructed from organic linkers and metal ions or clusters, have raised significant interests for biocatalysts immobilization in recent years. The diversity of building units, molecular-scale tunability, and modular synthetic routes of MOFs greatly expand its ability as the host to integrate with biocatalysts. In this review, the general synthetic strategies of MOFs with biocatalysts are first summarized. Then, the recent progress of MOFs as a versatile host for a series of biocatalysts, including natural enzymes, nanozymes, and organism-based biocatalysts, followed by the introduction of MOFs themselves as biocatalysts, is discussed. Furthermore, the stimuli-responsive properties of MOFs themselves or the additional functionalization of protein, polymer, and peptide within/on MOF that enable the biocatalysts with the controllable and tunable behavior are also summarized, which could unlock new potentials in biocatalysis. Finally, a perspective of the upcoming challenges, potential impacts, and future directions of biocatalytic MOFs is provided.

MIL-160 as an Adsorbent for Atmospheric Water Harvesting

Nowadays, the rapidly growing population, climate change, and environment pollution put heavy pressure on fresh water resources. The atmosphere is the immense worldwide and available water source. The Adsorptive Water Harvesting from the Atmosphere (AWHA) method is considered a promising alternative to desalination technologies for remote arid regions. The development of novel adsorbents with advanced water-adsorption properties is a prerequisite for practical realization of this method. Metal–organic frameworks (MOFs) are a novel class of porous crystalline solids that bring a great potential for AWHA due to their extremely high specific surface area, porosity, and tailored adsorption properties. This work addresses MIL-160 as a water adsorbent for AWHA. The water-adsorption equilibrium of MIL-160 was studied by volumetric method, the isosteric heat of adsorption was calculated, and finally, the potential of MIL-160 for AWHA was evaluated for climatic conditions of the deserts of Saudi Arabia, Mongolia, the Sahara, Atacama, and Mojave as reference arid regions. MIL-160 was shown to ensure a maximum specific water productivity of 0.31–0.33 gH2O/gads per cycle. High fractions of water extracted (0.90–0.98) and collected (0.48–0.97) could be achieved at a regeneration temperature of 80 °C with natural cooling of the condenser by ambient air. The specific energy consumption for water production varied from 3.5 to 6.8 kJ/g, which is acceptable if solar heat is used to drive the desorption. The AWHA method employing MIL-160 is a promising way to achieve a fresh water supply in remote arid areas.

Thin Films of Metal-Organic Framework Interfaces Obtained by Laser Evaporation

Properties such as large surface area, high pore volume, high chemical and thermal stability, and structural flexibility render zeolitic imidazolate frameworks (ZIFs) well-suited materials for gas separation, chemical sensors, and optical and electrical devices. For such applications, film processing is a prerequisite. Herein, matrix-assisted pulsed laser evaporation (MAPLE) was successfully used as a single-step deposition process to fabricate ZIF-8 films. By correlating laser fluency and controlling the specific transfer of lab-synthesized ZIF-8, films with user-controlled physical and chemical properties were obtained. Films' characteristics were evaluated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The analysis showed that frameworks of ZIF-8 can be deposited successfully and controllably to yield polycrystalline films. The deposited films maintained the integrity of the individual ZIF-8 framework, while undergoing minor crystalline and surface chemistry changes. No significant changes in particle size were observed. Our study demonstrated control over both the MAPLE deposition conditions and the outcome, as well as the suitability of the listed deposition method to create composite architectures that could potentially be used in applications ranging from selective membranes to gas sensors.

Active Nanointerfaces Based on Enzyme Carbonic Anhydrase and Metal-Organic Framework for Carbon Dioxide Reduction

Carbonic anhydrases are enzymes capable of transforming carbon dioxide into bicarbonate to maintain functionality of biological systems. Synthetic isolation and implementation of carbonic anhydrases into membrane have recently raised hopes for emerging and efficient strategies that could reduce greenhouse emission and the footprint of anthropogenic activities. However, implementation of such enzymes is currently challenged by the resulting membrane’s wetting capability, overall membrane performance for gas sensing, adsorption and transformation, and by the low solubility of carbon dioxide in water, the required medium for enzyme functionality. We developed the next generation of enzyme-based interfaces capable to efficiently adsorb and reduce carbon dioxide at room temperature. For this, we integrated carbonic anhydrase with a hydrophilic, user-synthesized metal–organic framework; we showed how the framework’s porosity and controlled morphology contribute to viable enzyme binding to create functional surfaces for the adsorption and reduction of carbon dioxide. Our analysis based on electron and atomic microscopy, infrared spectroscopy, and colorimetric assays demonstrated the functionality of such interfaces, while Brunauer–Emmett–Teller analysis and gas chromatography analysis allowed additional evaluation of the efficiency of carbon dioxide adsorption and reduction. Our study is expected to impact the design and development of active interfaces based on enzymes to be used as green approaches for carbon dioxide transformation and mitigation of global anthropogenic activities.

Lysozyme Adsorption on Porous Organic Cages: A Molecular Simulation Study

Recently, porous organic cages (POCs) have emerged as a novel porous material with many merits and are widely utilized in many application fields. In this work, for the first time, molecular dynamics simulations were performed to investigate the mechanism of lysozyme adsorption onto the CC3 crystal, a kind of widely studied POC material. The simulation results show that lysozyme adsorbs onto the surface of CC3 with "top end-on," "back-on," or "side-on" orientations. It is found that the van der Waals interaction is the primary contribution to the binding; the conformation of the lysozyme is well preserved during the adsorption process. This provides some evidence for its biocompatibility and feasibility in biorelated applications. Arginine plays an important role in mediating the adsorption through nonpolar aliphatic chains. More importantly, the distribution and structure of the water layer on the POC surface has a significant impact on adsorption. This study provides insights into the development of POC materials with defined morphologies for the adsorption of biomolecules and may help the rational design of biorelated systems.

Electrostatic Effect of Functional Surfaces on the Activity of Adsorbed Enzymes: Simulations and Experiments

The efficient immobilization of haloalkane dehalogenase (DhaA) on carriers with retaining of its catalytic activity is essential for its application in environmental remediation. In this work, adsorption orientation and conformation of DhaA on different functional surfaces were investigated by computer simulations; meanwhile, the mechanism of varying the catalytic activity was also probed. The corresponding experiments were then carried out to verify the simulation results. (The simulations of DhaA on SAMs provided parallel insights into DhaA adsorption in carriers. Then, the theory-guided experiments were carried out to screen the best surface functional groups for DhaA immobilization.) The electrostatic interaction was considered as the main impact factor for the regulation of enzyme orientation, conformation, and enzyme bioactivity during DhaA adsorption. The synergy of overall conformation, enzyme substrate tunnel structural parameters, and distance between catalytic active sites and surfaces codetermined the catalytic activity of DhaA. Specifically, it was found that the positively charged surface with suitable surface charge density was helpful for the adsorption of DhaA and retaining its conformation and catalytic activity and was favorable for higher enzymatic catalysis efficiency in haloalkane decomposition and environmental remediation. The neutral, negatively charged surfaces and positively charged surfaces with high surface charge density always caused relatively larger DhaA conformation change and decreased catalytic activity. This study develops a strategy using a combination of simulation and experiment, which can be essential for guiding the rational design of the functionalization of carriers for enzyme adsorption, and provides a practical tool to rationally screen functional groups for the optimization of adsorbed enzyme functions on carriers. More importantly, the strategy is general and can be applied to control behaviors of different enzymes on functional carrier materials.

Fast Immobilization of Human Carbonic Anhydrase II on Ni-Based Metal-Organic Framework Nanorods with High Catalytic Performance

Carbonic anhydrase (CA) has received considerable attention for its ability to capture carbon dioxide efficiently. This study reports a simple strategy for immobilizing recombinant carbonic anhydrase II from human (hCA II) on Ni-based MOFs (Ni-BTC) nanorods, which was readily achieved in a one-pot immobilization of His-tagged hCA II (His-hCA II). Consequently, His-hCA II from cell lysate could obtain an activity recovery of 99% under optimal conditions. After storing for 10 days, the immobilized His-hCA II maintained 40% activity while the free enzyme lost 91% activity. Furthermore, during the hydrolysis of p-nitrophenyl acetic acid, immobilized His-hCA II exhibited excellent reusability and still retained more than 65% of the original activity after eight cycles. In addition, we also found that Ni-BTC had no fixation effect on proteins without histidine-tag. These results show that the Ni-BTC MOFs have a great potential with high efficiency for and specific binding of immobilized enzymes.

Toxicity screening of two prevalent metal organic frameworks for therapeutic use in human lung epithelial cells

INTRODUCTION

The flexibility and tunability of metal organic frameworks (MOFs), crystalline porous materials composed of a network of metal ions coordinated by organic ligands, confer their variety of applications as drug delivery systems or as sensing and imaging agents. However, such properties also add to the difficulty in ensuring their safe implementation when interaction with biological systems is considered.

METHODS

In the current study, we used real-time sensorial strategies and cellular-based approaches to allow for fast and effective screening of two MOFs of prevalent use, namely, MIL-160 representative of a hydrophilic and ZIF-8 representative of a hydrophobic framework. The two MOFs were synthesized "in house" and exposed to human bronchial epithelial (BEAS-2B) cells, a pertinent toxicological screening model.

RESULTS

Analysis allowed evaluation and differentiation of particle-induced cellular effects as well identification of different degrees and routes of toxicity, all in a high-throughput manner. Our results show the importance of performing screening toxicity assessments before introducing MOFs to biomedical applications.

DISCUSSION

Our proposed screening assays could be extended to a wider variety of cell lines to allow for identification of any deleterious effects of MOFs, with the range of toxic mechanisms to be differentiated based on cell viability, morphology and cell-substrate interactions, respectively.

CONCLUSION

Our analysis highlights the importance of considering the physicochemical properties of MOFs when recommending a MOF-based therapeutic option or MOFs implementation in biomedical applications.

Metal-Organic Framework-Based Composite for Photocatalytic Detection of Prevalent Pollutant

Photocatalytic properties of 2,5-furandicarboxylic acid (FDCA), a model organic molecule used for biopolymer production, are reported for the first time. Further integration of FDCA into metal-organic framework (MOF) structures and subsequent silver-based photoactivation leads to the next generation of hybrids with controlled morphologies, capable of forming sensorial platforms for prevalent phenol contaminant detection. The mechanisms that allow photocatalytic functionality are driven by the charge carrier generation in the organic molecule (either in its alone or integrated form) and depend on sample's physical and chemical properties as confirmed by scanning and transmission electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. Electrochemical analysis using cyclic voltammetry confirmed high sensitivity for p-nitrophenol (p-NP) detection as dictated by the selective electron migration at a user-controlled electrode interface. Considering the wide usage of p-NP and its increased discharge shown to lead to harmful effects on both the environment and biosystems, this new detection method is envisioned to allow effective control and regulation of such compound release, all under low-cost and environmentally friendly conditions.