Zeolitic Imidazolate Framework-8 Structure Research Articles

Construction of enzyme-MOFs composite with carbon dots: A strategy to enhance the activity and increase the growth rate of the enzyme-ZIF-8 composite.

Encapsulating enzymes in metal-organic frameworks (MOFs) enhances enzyme protection and improves the accuracy of inhibitor recognition and screening. Zeolitic imidazolate framework-8 (ZIF-8) has been widely used as a host matrix for enzyme immobilization. However, challenges such as the microporous structure and hydrophobicity of ZIF-8, along with the protonation of 2-methylimidazole, hinder the maintenance of activity and the rapid formation of composite. Herein, a new strategy to synthesize novel enzyme-MOFs composite by encapsulating carbon dots (CDs)-modified enzyme and Fe3O4 nanoparticles within ZIF-8 is presented for the first time. The contribution of CDs in enzyme-MOFs composite was investigated. Characterizations reveal that the CDs-modified enzymes compete with imidazole for Zn ions, inducing mesoporous structures that alleviate diffusion limitations. Modification of enzyme with CDs also modulates enzyme-MOFs interfacial interactions, accelerating the formation of composite. Activity evaluation shows that enzyme-MOFs composite (THR@CDs/Fe3O4@ZIF-8) retains 81.76% enzyme activity under harsh conditions and maintains 66.0% of the initial enzyme activity after 10 reuse cycles. This synthesis strategy for the novel enzyme-MOFs composite was proven to be universal. The Km value of THR@CDs/Fe3O4@ZIF-8 (19.32μM) is lower than that of THR/Fe3O4@ZIF-8, indicating that modification with CDs significantly increases the affinity of enzyme. Furthermore, THR@CDs/Fe3O4@ZIF-8 was effectively utilized for enzyme inhibitor recognition and screening. These results demonstrate that the proposed method is a universal approach for rapidly and controllably fabricating enzyme-ZIF-8 composite with elevated activity and exceptional stability, offering promising potential for advanced drug recognition and screening platforms.

Hydrophilic Metal-Organic Frameworks Regulated by Biomineralized Protein for Enhanced Stability and Drug Delivery.

For bridging the gap between biological and synthetic materials, the fusion of Metal-Organic Frameworks (MOFs) with biological entities has emerged as a revolutionary strategy in functional materials. In this context, our study introduces a novel structure wherein Bovine Serum Albumin (BSA), a robust and versatile protein, encapsulates zeolitic imidazolate framework-8 (ZIF-8), forming a protein-caged MOF. Highlighting the advantages of this innovative design, the protein-encapsulation enhances the stability and dispersity of ZIF-8, and aids in the synthesis of smaller-sized nanoparticles, crucial for size-impact performance applications. Additionally, the BSA-caged ZIF-8 structure showcases potential in drug delivery applications, especially in the controlled delivery of chemotherapeutic drugs. The study thus elucidates the multifaceted applicability of this novel structure, marking a significant stride in the convergence of biological and synthetic materials.

A novel ZIF-8 mediated nanocomposite colorimetric sensor array for rapid identification of matcha grades, validated by density functional theory

The rapid and intelligent assessment of matcha grades remains crucial in quality control. This study proposed a colorimetric sensor array (CSA) mediated with zeolitic imidazolate framework-8 (ZIF-8) to identify matcha grades. The ZIF-8 mediated CSA was innovatively developed by encapsulating the pH indicator and metal porphyrin within the ZIF-8 structure, improving their stability and functionality. ZIF-8 mediated CSA exhibited significantly increased sensitivity towards matcha samples driven by the preconcentration of volatile organic compounds (VOCs) facilitated by ZIF-8. As a result, the response signal values of the CSA increased by 1.13–4.75 times after ZIF-8 mediation. Subsequently, qualitative models for identifying matcha grades were established using K-Nearest Neighbor and Artificial Neural Network (ANN). The ANN model showed the higher discrimination accuracy. Compared with common CSA, the ANN model based on ZIF-8 mediated CSA achieved a better identification rate of 95 %, and recognition accuracy was improved by 7.5 % in the model. These results indicated that the ZIF-8 mediated CSA with a porous structure demonstrated enhanced specificity in capturing VOCs. Ultimately, the density functional theory has confirmed that the ZIF-8-mediated CSA exhibits high selectivity towards matcha's characteristic VOCs. These results highlight the potential of this novel CSA for the rapid identification and grading of matcha.

Preparation of IL@ZIF-8 composite as a new adsorbent for preconcentration of Cd (II) and Co (II) ions from environmental samples with vortex-assisted dispersive solid phase microextraction

Ionic liquid (IL) was incorporated into a zeolitic imidazolate framework-8 (ZIF-8) under mild conditions. (1)-methylimidazole and 1-bromobutane were combined to form the IL inside the pore structure of ZIF-8 using the ship-in-bottle (SIB) method. The IL@ZIF-8 composite has been thoroughly characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller analysis (BET), and Fourier transform infrared spectroscopy (FTIR). IL@ZIF-8 composite was used as a new adsorbent For the preconcentration and measurement of Cd (II) and Co (II) ions in a variety of sample matrices, such as soil, vegetable juice, and water. This methodology was achieved by integrating vortex-assisted dispersive solid phase microextraction (VA-DSPME) and flame atomic absorption spectrometry (FAAS). Under optimal conditions, the method demonstrated a favorable linear dynamic range within the range of 0.001–2 and 0.008–10 µg mL−1, with a lower limit of detection values of 0. 33 and 2.42 µg/L for Cd (II) and Co (II) ions, respectively. Furthermore, the method preconcentration factor was 25 for both metal ions. The relative standard deviations (RSDs) of this work were found to be below 1.0 % for the concentration of 0.5 µg mL−1.

An investigation on the structural stability of ZIF-8 in water versus water-derived oxidative species in aqueous environment

The zeolitic-imidazolate-framework-8 (ZIF-8) is one of the extensively studied metal-organic frameworks (MOF) materials because of its unique structure. For its potential applicability in numerous fields, it becomes crucial to have detailed studies on the structural stability of ZIF-8, especially in aqueous environments. A number of studies have been conducted to investigate the breakdown process of the ZIF-8 structure in water; which is known as the hydrolysis of ZIF-8. However, those studies reported different opposing experimental observations on the role of water on the structural stability of ZIF-8, which created obscurity in understanding this phenomenon. This study explored the effects of different water-derived species on the structural stability of ZIF-8; specifically, examined the effects of only water and water with different oxidative species that may be generated by water molecules' dissociation under external energy or catalyst presence. To this effort, we experimentally probed the physical and chemical structural changes of ZIF-8 in DI water and three different solutions of hydrogen peroxides (H2O2); taking H2O2 as the source of oxidative species. To assess the changes in elemental compositions, chemical bonds, functional groups, crystal structure, and morphology, all the samples were analyzed by X-ray photoelectron spectroscopy (XPS), energy-dispersive x-ray (EDX) spectroscopy, Fourier Transform Infrared (FTIR) spectroscope, X-ray diffractometer (XRD), and scanning electron microscope (SEM). Significant structural changes in ZIF-8 occurred mainly in the presence of oxidative species in water. Notably, oxidative species’ concentration exceeding 1 M heightened the deformation of the ZIF-8 structure.

Targeted Elimination of Surface Defects in Carbon Fibers: Formation of a Hybrid Structure Combining Rigidity with Flexibility from Sonochemical-Induced Directional Growth of Nano-ZIF-8 and Subsequent Annealing.

Currently, the mechanical performance of carbon fibers (CFs) has yet to fully realize its theoretical potential. This is predominantly attributed to the significant constraints posed by surface defects, greatly impeding the widespread application of carbon fibers. In order to address this issue, we employed a sonochemical-induced approach in this study to achieve in situ growth of nanoscale zeolitic imidazolate framework-8 (ZIF-8) at the surface defects of carbon fibers. After high-temperature treatment, the structure of ZIF-8 decomposed into ZnO and inorganic carbon, reinforcing the carbon fiber structure from both flexible and rigid aspects. Our research indicates that when the temperature reaches 500 °C, a substantial portion of ZIF-8 undergoes thermal decomposition, giving rise to zinc oxide and inorganic carbon. The flexible inorganic carbon and rigid ZnO form a meshlike structure, which welds to the surface defects of carbon fibers, resulting in strong interactions and contributing to the delay of fiber fracture. Compared to unmodified carbon fibers, the mechanical performance increased by approximately 15.86%. Based on the aforementioned analysis, this method can be considered a direct and effective approach for reinforcing carbon fiber structures, presenting a novel approach for the precise elimination of surface defects on carbon fibers.

Individually Tailored Modular "Egg" Hydrogels Capable of Spatiotemporally Controlled Drug Release for Spinal Cord Injury Repair.

Controllable drug delivery systems (DDS) can overcome the disadvantages of conventional drug administration processes, such as high dosages or repeated administration. Herein, we deploy a smart DDS collagen hydrogel for spinal cord injury (SCI) repair based on modular designing of "egg" nanoparticles (NPs) that ingeniously accomplish controlled drug release via inducing a signaling cascade in response to external and internal stimuli. The "egg" NPs consist of a three-layered structure: tannic acid/Fe3+ /tetradecanol "eggshell," zeolitic imidazolate framework-8 (ZIF-8) "egg white," and paclitaxel "yolk". Then NPs served as a crosslinking epicenter, blending with collagen solutions to generate functional hydrogels. Remarkably, the "eggshell" efficiently converts near-infrared (NIR) irradiation into heat. Subsequently, tetradecanol can be triggered to disintegrate via heat, exposing the structure of ZIF-8. The Zn-imidazolium ion coordination bond of the "egg white" was susceptible to cleaving at the acidic SCI site, decomposing the skeleton to release paclitaxel on demand. As expected, the paclitaxel release rate upon NIR irradiation increased up to 3-folds on the seventh day, which matches endogenous neural stem/progenitor cell migration process. Taken together, the collagen hydrogels facilitated the neurogenesis and motor function recovery, demonstrating a revolutionary strategy for spatiotemporally controlled drug release and providing guidelines for the design of DDS. This article is protected by copyright. All rights reserved.

Efficient recovery of C2+ alkanes from natural gas using porous ZIF-8/iso-hexadecane slurry on laboratory and pilot-scale

The efficient recovery of C2+ alkanes from natural gas is of great significance since the C2+ alkanes are the essential petrochemical raw material. This paper presents the novel absorption-adsorption hybrid method to recover the C2+ alkanes components from natural gas using a flowable zeolitic imidazolate framework-8 (ZIF-8)/iso-hexadecane slurry. The ZIF-8 particles have an excellent dispersion in the iso-hexadecane solvent. The sorption capacity for C2H6 and C3H8 in the slurry is significantly higher than that for CH4. Moreover, in competitive adsorption, the slurry showed a significant advantage for C2H6 and C3H8 over CH4. In the experiments of recovering C2+ alkanes from natural gas, the recovery ratio can reach a staggering 91.59%. Besides, in the regeneration tests, 97.79% of the sorption capacity for C2H6 can be recovered by vacuuming without temperature swings, and the characteristic structure of the recycled ZIF-8 remains intact. More encouragingly, a continuous pilot separation plant was established, and the test results show that the recovery ratio for C2+ alkanes can reach 86.75%. The excellent selective recovery performance is comparable to the mature cryogenic separation process. To our knowledge, this is the first time to apply metal–organic frameworks (MOFs) to separate natural gas on pilot-scale. This work has thus furthered the industrial application of MOFs in gas separation.

Bioinspired aldehyde-free and durable coatings for antibacterial, UV-resistant and flame-retardant cotton fabrics by the covalent bonding and in-situ coprecipitation

The development of functional and durable coatings is an effective solution for obtaining the satisfactory properties of cotton fabrics. Herein, the aldehyde-free and durable cotton fabrics (CZIF-8@CF) with well antibacteria, UV-resistance and flame retardancy had been obtained via an interfacial reaction strategy, where the well-organized zeolitic imidazolate framework-8 (ZIF-8) was in-situ grew on cotton fabrics pre-modified with chitosan (CS) and Zn ion. CZIF-8@CF displayed excellent antibacterial performances with 99.99 % antibacterial rates for both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Besides, the resulted cotton fabrics exhibited less than 5 % UV transmittance. Flame behaviors tests proved that the multifunctional coatings acted as “physical barrier” to reduce the heat produce coming from the synergistic effect of catalytic charring and high residual protection under high temperature of CZIF-8, and “vacuum cleaner” to decrease the smoke release resulting from the self-porous structure of ZIF-8. Even after 50 washing cycles, the CZIF-8@CF still showed less than 5 % UV transmittance, 99.99 % and 93.67 % antibacterial rates of S. aureus and E. coli, respectively. It was demonstrated that the covalent bonding between CS and part of Zn2+ in ZIF-8 could promote the durable antibacteria, UV-resistance and flame retardancy of cotton fabrics.

A novel core-shell structured Fe@CeO2-ZIF-8 catalyst for the reduction of NO by CO

Zeolitic imidazolate framework-8 (ZIF-8) based catalysts are considered as promising candidates for the selective catalytic reduction of NO by CO (CO-SCR) reaction due to their large specific surface area. However, the structure of ZIF-8 will be damaged during the synthesis procedure of the catalyst, leading to a decrease in their physical properties, which in turn affects the catalytic performance of the catalyst. Herein, a CeO2-ZIF-8 core-shell structure was synthesized and doped with Fe, resulting in the formation of Fe@CeO2-ZIF-8, for CO-SCR reaction. Characterization results show that the Fe@CeO2-ZIF-8 core-shell catalyst has better morphology, thermal stability, and higher specific surface area than the FeCe co-impregnated ZIF-8 catalyst (FeCe@ZIF-8 (IM)). Moreover, the reducibility of the reactive Fe species in the Fe@CeO2-ZIF-8 core-shell catalyst is also enhanced. As a result, the Fe@CeO2-ZIF-8 core-shell catalyst exhibited higher low-temperature CO-SCR catalytic activity with its NO conversion reaching 99% at 250 °C versus the FeCe@ZIF-8 (IM) catalyst (89% at 250 °C). The experimental results were further verified by density functional theory (DFT) calculations including Electron Localization Function (ELF), Valence Charge Density Difference (VCDD), Projected Density of States (PDOS) and Bader charge analyses. The calculation results revealed that the core-shell configured Fe@CeO2-ZIF-8 catalyst has a stronger active metal-support charge transfer and better capacity for the adsorption of the reactants. The reaction mechanism over Fe@CeO2-ZIF-8 core-shell catalyst was investigated via in situ DRIFTS experiments, and results showed that the nitro compounds and formate species are critical intermediates in this reaction at a higher temperature range (300–350 °C). This work provides a new strategy for the synthesis of ZIF-8 based catalysts with better properties for CO-SCR reaction.

Electrodeposition of Ag/ZIF-8-Modified Membrane for Water Remediation.

Metal-organic framework (MOF)-based membranes have been widely used in gas and liquid separation due to their porous structures and tunable compositions. Depending on the guest components, heterostructured MOFs can exhibit multiple functions. In the present work, we report a facile and rapid preparation of zeolitic imidazolate framework-8 (ZIF-8) and silver nanoparticle incorporated ZIF-8 (Ag/ZIF-8)-based membranes on stainless-steel mesh (SSM) through a "green" electrodeposition method. The SSM was first coated with a Zn-plated layer which contains mainly zinc hydroxide nitrate (Zn5(OH)8(NO3)2·2H2O) with a "leaf-like" morphology, providing anchoring points for the deposition of ZIF-8 and Ag/ZIF-8. It takes only 10 min to prepare a uniform coating of Zn5(OH)8(NO3)2·2H2O in aqueous conditions without the use of a strong base; this is by far the most efficient way of making zinc hydroxide nitrate nanocrystals. Following a similar electrodeposition approach, ZIF-8 and Ag/ZIF-8-coated SSM can be prepared within 20 min by applying a small current. The encapsulation of Ag does not alter the chemical composition nor the crystal structure of ZIF-8. The resulting ZIF-8 and Ag/ZIF-8-coated SSM have been tested for their effectiveness for rhodamine B dye removal in a fast vacuum filtration setting. Additionally, growth of E. coli was significantly inhibited after overnight incubation with Ag/ZIF-8-coated SSM. Overall, we demonstrate a fast synthesis procedure to make ZIF-8 and Ag/ZIF-8-coated SSM membranes for organic dye removal with excellent antimicrobial activity.

Metal-organic-framework-based pyroptosis nanotuner with long blood circulation for augmented chemotherapy.

Pyroptosis is a proinflammatory form of cell death mediated by members of the gasdermin family, and is a powerful tool against cancer. Herein, a pH-responsive doxorubicin (DOX)-encapsulating zeolitic imidazolate framework-8 (ZIF-8) nanoparticle coated with a carboxybetaine-based zwitterionic polymer (DOX@ZIF-8@PCBMA) was prepared. Furthermore, decitabine (DAC) was loaded to obtain a pyroptosis nanotuner (DOX@ZIF-8@PCBMA-DAC). This nanotuner displayed extended blood circulation and enhanced tumor accumulation. In addition, the ZIF-8 structure and disulfide-crosslinked PCBMA coating endowed DOX@ZIF-8@PCBMA-DAC with acidic-pH- and glutathione-responsive degradation. The nanotuner could robustly activate caspase-3 to induce gasdermin E (GSDME)-dependent pyroptosis via the sustained release of DAC and DOX, contributing to excellent tumor suppression with negligible side effects, which may provide novel insights into traditional chemotherapy.

Zeolitic imidazolate framework-8 encapsulating gold nanoclusters and carbon dots for ratiometric fluorescent detection of adenosine triphosphate and cellular imaging

A novel nanoprobe was prepared by encapsulating carbon dots (CDs) and gold nanoclusters (AuNCs) into zeolitic imidazolate framework-8 (ZIF-8) for sensitive detecting adenosine triphosphate (ATP). Under excitation at 360 nm, the obtained CDs/AuNCs@ZIF-8 nanoprobe exhibits dual-emissions at 469 nm and 660 nm, respectively, corresponding to the fluorescence emission of CDs and the aggregation-induced emission enhancement (AIEE) of AuNCs. The framework of ZIF-8 in this probe can be degraded by ATP due to the coordination competition of ATP and 2-Methylimidazole towards zinc ion (Zn2+), resulting in the release of CDs and AuNCs. The following dispersion of CDs would improve efficiencies of the fluorescence excitation and the consequent emission of CDs. On the contrary, the AIEE of AuNCs would be decreased spontaneously after the AuNCs originally restricted in ZIF-8 were allowed to escape. The intensity ratio of fluorescence at 469 nm to that at 660 nm (I469/I660) was conveniently employed as the response signal for representing the amount of ATP. This nanoprobe exhibits excellent sensitivity and selectivity toward ATP, with a limit of detection (LOD) of 0.061 μM. Besides, low cytotoxicity of this nanoprobe facilitates its application as a fluorescent indicator in fluorescence imaging of living cells. Encapsulating two types of fluorescent nanomaterials by a degradable ZIF-8 structure makes the ratiometric fluorescence response of the nanocomposite probe towards the target analyte that destroys the ZIF-8 structure possible, and simplifies the application of the probe.

ZIF-8 and Its Magnetic Functionalization as Vehicle for the Transport and Release of Ciprofloxacin.

The use of nanomaterials for the controlled release of drugs aims to enhance their effectiveness, especially when poorly soluble in water, and achieve their rapid, localized, and effective administration. The present study focuses on the use of a Zeolitic Imidazolate Framework-8 (ZIF-8) as vehicle for the transport and controlled release of the antibiotic ciprofloxacin (CIP) as model due to its favorable physicochemical characteristics. The objective is to synthesize the ZIF-8 material loaded with CIP through encapsulation for subsequent release of the drug in neutral and acid physiological media. In addition, functionalization of the CIP/ZIF compound with magnetic nanoparticles (NP) was sought to increase its traceability through the possible use of magnetic fields. Characterizations by XRD, FT-IR, SEM-EDX, and TGA showed a satisfactory synthesis of both pure ZIF-8 and ciprofloxacin-loaded ZIF-8, with high crystallinity and thermal stability. The release profiles showed an abrupt initial release that stabilized over time. A much higher release (20-80% greater) was obtained in acid versus neutral pH in all cases, attributable to the collapse of the ZIF-8 structure in acid media. In addition, functionalization of the material with iron NPs did not affect the behavior of the system during drug release. Antimicrobial activity tests against E. coli and S. aureus showed that ZIF-8 per se exerts antimicrobial activity, while the compounds CIP/ZIF and magnetic CIP/ZIF increased the antimicrobial capacity of pure CIP by 10-20%. The ZIF-8 system has high potential as a drug carrier and release agent for the treatment of diseases, especially those that cause acidification of the cellular environment, achieving a rapid, localized, and targeted action with the possibility of achieving traceability of the system after its magnetic functionalization.

Exploring the Influence of the Reused Methanol Solution for the Structure and Properties of the Synthesized ZIF-8

The zeolitic imidazolate framework-8 (ZIF-8), as a kind of MOF, is widely used in sensors, gas storage/separation, drug delivery, and catalysis due to its adjustable porous structure, high surface area, and excellent chemistry tunability. ZIF-8 is constructed by Zn2+ and 2-methylimidazole and synthesized in the methanol solution. In this paper, we explored the influence of the reused methanol solution for the structure and properties of the synthesized ZIF-8. The as-synthesized ZIF-8 was characterized by an X-ray diffraction instrument (XRD), a scanning electron microscope (SEM), a specific surface area analyzer (BET), and Fourier transform infrared spectroscopy (FT-IR). The results show that the reused methanol solution does not change the phase, porous structure, and BET surface area of ZIF-8. However, the particle size of ZIF-8 increases from 50 nm to 5 um and the productive rate decreases to 7.4% when the methanol solution is reused four times. This work provides new insight into the reuse of dissolvents for the synthesis of MOFs.

Enhanced stability of Ti3C2Tx MXene enabled by continuous ZIF-8 coating

MXenes have recently attracted significant interest owing to their outstanding properties and performance. However, their hydrophilic and metastable surfaces make most MXenes prone to oxidation, which can greatly degrade their properties and hinder their practical applications. Here, we enhanced the stability of Ti3C2Tx MXene films by coating a continuous zeolitic imidazolate framework-8 (ZIF-8) layer. The high-density oxygen functional groups of MXene, which are crucial for inducing the nucleation of ZIF-8 crystals, were merged into a continuous layer on the MXene surface. 98% of the original electromagnetic interference shielding effectiveness of ZIF-8/Ti3C2Tx MXene was retained even after 4 days of harsh oxidation treatment at 85 °C and 85% RH. The enhanced stability could be attributed to the hydrophobic microporous structure of ZIF-8, which effectively hindered the permeation of water molecules in addition to terminating the dangling bonds of MXene with Zn ions.

Antibacterial Zeolite Imidazole Frameworks with Manganese Doping for Immunomodulation to Accelerate Infected Wound Healing.

Numerous nanomedicines currently emerge to reduce the dramatic threat in antibiotics resistance for antibacterial application against severe bacterial infections, while it is restricted by over-reacted immune response to pathogenic bacteria. Herein, enzymatic activity is introduced into the zeolitic imidazolate framework-8 (ZIF-8) to achieve sterilization by releasing Zn ions, as well as inflammation regulation through the variable valence of Mn ions that are uniformly doped into its framework. Within this simple metal organic framework (MOF) structure design, Mn-ZIF-8 possesses the co-existence of Mn2+ /Mn4+ to endow the nanocomposite with the anti-inflammatory capabilities, which can be adjusted through the redox environment. The enzymatic activity of Mn ions and superiority of pore structure of ZIF-8 are effectively combined to realize the substrate selection via reactant molecular size and high-efficiency internal catalytic performance. By such design, this nanocomposite would not only exhibit an excellent antibacterial performance against pathogenic bacteria, but also reshape the inflammatory immunity by regulating macrophage polarization to suppress over-reacted inflammation, leading to a favorably therapeutic efficiency on bacteria-infected wound healing in animal models. Taken together, this nanoplatform provides effective approach for accelerating infected wound healing via bacteria killing and inflammation modulation, and may be extended for the therapy of other severe bacteria-induced infections.

Cytotoxicity, oxidative stress, and apoptosis in human embryonic kidney (HEK293) and colon cancer (SW480) cell lines exposed to nanoscale zeolitic imidazolate framework 8 (ZIF-8).

Zinc (zeolitic) imidazolate framework 8 (ZIF-8) has been widely considered in the literature as an ideal candidate for drug delivery especially anti-cancer drugs. However, the available information on the biocompatibility and cytotoxicity of ZIF-8 nanoparticles is contradictory. Therefore, in the present study, the ZIF-8 particles were synthetized, characterized, and their potential toxicity on two eukaryotic cell lines including human embryonic kidney (HEK293) and human colon cancer (SW480) cells was investigated in vitro. The characterization of ZIF-8 particles by TEM, EDX, SEM, and DLS indicated the synthesis of the hexagonal crystals with mean diameter of 124.71±32.74 nm and the presence of the zinc element at 86.25% by weight (wt%) of the ZIF-8 structure. The results of the cytotoxicity assessment of ZIF-8 NPs showed that the viability of two different cell lines reduced significantly coincident with increasing exposure concentration from 0 to 500 μg mL-1 (P<0.05). The 24-h half-inhibitory concentration (IC50-24 h) values of ZIF-8 NPs for HEK293 and SW480 cell lines were 116.22 and 36.23 μg mL-1, respectively. We found that the viability of SW480 cells was significantly lower than the HEK293 cells in all exposure concentrations of ZIF-8 NPs except control. Exposure of both cells resulted in increasing of the intracellular reactive oxygen species (ROS) production and activation of apoptosis pathway. The apoptosis rate of cancer SW480 cells was higher than the normal HEK293 cells. These findings indicate that synthetized ZIF-8 NPs could be a candidate for cancer therapy, although their toxic effects on the normal cells also should be considered.

Enhancing osteoregenerative potential of biphasic calcium phosphates by using bioinspired ZIF8 coating

Biphasic calcium phosphate ceramics (BCPs) have been extensively used as a bone graft in dental clinics to reconstruct lost bone in the jaw and peri-implant hard tissue due to their good bone conduction and similar chemical structure to the teeth and bone. However, BCPs are not inherently osteoinductive and need additional modification and treatment to enhance their osteoinductivity. The present study aims to develop an innovative strategy to improve the osteoinductivity of BCPs using unique features of zeolitic imidazolate framework-8 (ZIF8). In this method, commercial BCPs (Osteon II) were pre-coated with a zeolitic imidazolate framework-8/polydopamine/polyethyleneimine (ZIF8/PDA/PEI) layer to form a uniform and compact thin film of ZIF8 on the surface of BCPs. The surface morphology and chemical structure of ZIF8 modified Osteon II (ZIF8-Osteon) were confirmed using various analytical techniques such as XRD, FTIR, SEM, and EDX. We evaluated the effect of ZIF8 coating on cell attachment, growth, and osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs). The results revealed that altering the surface chemistry and topography of Osteon II using ZIF8 can effectively promote cell attachment, proliferation, and bone regeneration in both in vitro and in vivo conditions. In conclusion, the method applied in this study is simple, low-cost, and time-efficient and can be used as a versatile approach for improving osteoinductivity and osteoconductivity of other types of alloplastic bone grafts.

Chiral Macroporous MOF Surfaces for Electroassisted Enantioselective Adsorption and Separation.

The development of surfaces with chiral features is a fascinating challenge for modern materials science, especially when they are used for chiral separation technologies. In this contribution, the design of hierarchically structured chiral macroporous zeolitic imidazolate framework-8 (ZIF-8) electrodes is presented. They are elaborated by an electrochemical deposition-dissolution technique based on the electrodeposition of metal through a colloidal crystal template, followed by controlled electrooxidation. This generates locally metal cations, which can interact with a chiral ligand present in the solution to form metal-organic frameworks (MOFs). The macroporous structure facilitates the access of the chiral recognition sites, located in the mesoporous MOF, and thus helps to overcome mass transport limitations. The efficiency of the designed functional materials for chiral adsorption and separation can be fine-tuned by applying an adjustable electric potential to the electrode surfaces. This hierarchical chiral ZIF-8 structure was deposited at the walls of a microfluidic device and used as a stationary phase for enantioselective separation. The potential-controlled interaction between the stationary phase and the chiral analytes allows baseline separation of two enantiomers. This opens up interesting perspectives for using hierarchically structured chiral MOFs as an efficient material for the selective adsorption and separation of chiral compounds.