Zeolitic Imidazolate Framework-8 Nanoparticles Research Articles

Enhancement of proton conductivity of crosslinked poly(vinyl alcohol) through introduction of zeolitic imidazolate framework-8 and imidazole

Proton exchange membranes from crosslinked poly(vinyl alcohol) using sulfosuccinic acid (SSA) and glutaraldehyde as double crosslinking agents were reported. The effect of SSA content on water uptake and proton conductivity was investigated. The most promising membrane was then formed into composites with zeolitic imidazolate framework-8 (ZIF-8). ZIF-8 was synthesized, and confirmed by Fourier transform infrared spectroscopy, X-ray diffraction analysis, and transmission electron microscopy. The effect of ZIF-8 loading (0–10%) on membrane properties was firstly reported. Relatively good dispersion of ZIF-8 nanoparticles was observed for composites with %loadings up to 5%. The enhancements in proton conductivity and mechanical strength were observed upon ZIF-8 addition, and the optimum loading was 5%. In an attempt to improve proton conductivity at low relative humidity, the composite was further doped with imidazole. Proton conductivity increased with increasing imidazole content and temperature, and reached a maximum of 2.3 × 10−4 S/cm at 80 °C under non-humidified condition.

Encapsulation of Enzymes in Metal-Phenolic Network Capsules for the Trigger of Intracellular Cascade Reactions.

Nanoengineered capsules encapsulated with functional cargos (e.g., enzymes) are of interest for various applications including catalysis, bioreactions, sensing, and drug delivery. Herein, we report a facile strategy to engineer enzyme-encapsulated metal-phenolic network (MPN) capsules using enzyme-loaded zeolitic imidazolate framework nanoparticles (ZIF-8 NPs) as templates, which can be removed in a mild condition (e.g., ethylenediaminetetraacetic acid (EDTA) solution). The capsule size (from 250 nm to 1 μm) and thickness (from 9.8 to 33.7 nm) are well controlled via varying the template size and coating time, respectively. Importantly, MPN capsules encapsulated with enzymes (i.e., glucose oxidase) can trigger the intracellular cascade reaction via the exhaustion of glucose to produce H2O2 and subsequently generate toxic hydroxyl radicals (•OH) based on the Fenton reaction via the reaction between H2O2 and iron ions in MPN coatings. The intracellular cascade reaction for the generation of •OH is efficient to inhibit cancer cell viability, which is promising for the application in chemodynamic therapy.

Mixed Solvent Method for Improving the Size Uniformity and Cargo-Loading Efficiency of ZIF-8 Nanoparticles.

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles with tunable diameters and a uniform morphology were constructed in dimethyl sulfoxide (DMSO)/H2O mixed solvents and were further decorated with dextran to improve their stability and biocompatibility. A series of reaction conditions, including the DMSO content in mixed solvents, molar ratio between precursors, growth time, and decoration of dextran, were systematically investigated. Most importantly, it was the union of DMSO and water that achieved the combined merits of both solvothermal and hydrothermal methods, namely, high uniformity and high efficiency, respectively. In addition, numerous properties of these ZIF-8 nanoparticles were subsequently studied, such as the crystal structure, surface properties, and porosity. Furthermore, composite ZIF-8 nanoparticles encapsulating various functional molecules were also successfully prepared in the same DMSO/H2O mixed solvents, thus laying the foundation for their application as nanocarriers in the biomedical field.

ZIF-8 Nanoparticles for Facile Processing into Useful Fabric Composites

Because of the importance of large-scale metal–organic framework (MOF) production and processing, the development of practical solutions to obtain commercially relevant MOF-based products is essential. Herein, we demonstrate a feasible pathway to construct functional zeolitic imidazolate framework-8 (ZIF-8)-coated fabric composite from commercially available precursors, through a scalable synthetic protocol to produce a large quantity of nanoscale ZIF-8, followed by a facile mean to drop-cast the powdered nanoparticles onto the fabric substrate. The ZIF-8/fabric composite shows enhanced organic dye adsorption capability and superior antibacterial property. This simple yet effective preparation process might be readily adopted for the large-scale production of useful MOF-based composite materials.

Selectivity Control in the Oxidative Ring-Opening of Dimethylfuran Mediated by Zeolitic-Imidazolate Framework-8 Nanoparticles

Selectivity Control in the Oxidative Ring-Opening of Dimethylfuran Mediated by Zeolitic-Imidazolate Framework-8 Nanoparticles

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.

Exploration of de novo‐ synthesized Zeolitic Imidazolate Framework‐8 (ZIF‐8) Nanoparticles as an Additive to Growth Media for Myoblasts

Skeletal muscle tissue engineering aims to repair a large area of damaged muscle caused by injuries or illness due to the difficulty of the cells naturally regenerating large tissue loss. Supplements help restore this loss via myoblast proliferation and maturation. Zinc excites the signal pathways for myogenesis, and as a supplement it should increase myoblast proliferation and maturation. The project goal was to synthesize nanoparticles that will stay suspended in cell media and allow the transfer of the zinc ion to increase muscle cell proliferation and maturation. Zeolitic imidazole framework-8 (ZIF-8) were created using a de novo synthesis, with the desired carboxaldehydes attached to the four imidazole rings surrounding a zinc ion core (Krishna et al. 2017). After synthesis, MP-AES, FT-IR, 13C-NMR, and 1H-NMR instruments were used to characterize the ZIF-8 nanoparticles. The synthesized product yields were 0.1098 g, 0.7400 g, and 0.1492 g, but the characterization data was inconsistent. 10 mg, 50 mg, and 100 mg of the synthesized products were then suspended in vials of 10 mL of phosphate buffered saline (PBS), sonicated for four, and six minutes with 20 seconds on and off, and the suspension time recorded. The 50 mg and 100 mg had the lowest suspension times (21 s to 162 s) while the 10 mg of product had higher suspension times (16 s to 384 s). In conclusion, the de novo ZIF-8 synthesis provided varying product yields; however, the suspendability times were too low. Ongoing research will focus on characterization, increasing the amount of zinc, and increasing the suspension time.

Hyaluronic acid coating on the surface of curcumin-loaded ZIF-8 nanoparticles for improved breast cancer therapy: An in vitro and in vivo study

Despite developments in surgery and chemotherapy, effective treatment of breast cancer is still an urgent problem owing to recurrence and metastasis. By combining the advantages of curcumin (Cur), zeolitic imidazolate framework-8 nanoparticles (ZIF-8), and hyaluronic acid (HA) in breast cancer therapy, Cur-loaded and HA-coated ZIF-8 (Cur@ZIF-8@HA) were synthesized using a method based on the pH-dependent solubility of Cur and the electrostatic interactions between zinc ions and carboxyl groups of HA. Cur@ZIF-8 were also prepared as a control group. Comprehensive comparisons of the physicochemical properties and anticancer activities of Cur@ZIF-8@HA and Cur@ZIF-8 were conducted. The results indicated that the degradation of Cur during the synthesis of Cur@ZIF-8 was negligible. The obtained Cur@ZIF-8 and Cur@ZIF-8@HA were truncated cubes with hydrodynamic diameters of 174 and 217 nm, respectively. Cur@ZIF-8@HA possessed better stability during storage in different media, a slower drug release rate under neutral and acidic conditions, and a greater inhibitory effect on breast cancer than Cur@ZIF-8. For 4T1 cells, treatment using Cur@ZIF-8@HA induced more cellular uptake and higher cytotoxicity, accompanied by higher lactate dehydrogenase release, cell cycle arrest in G2/M and S phases, production of reactive oxygen species, and apoptosis. In 4T1 tumor-bearing mice models, Cur@ZIF-8@HA showed a stronger inhibitory effect on tumor growth and pulmonary metastasis. Therefore, Cur@ZIF-8@HA might hold great potential as an agent for the effective therapy of breast cancer.

Zinc Metal-Organic Framework Growing on the Surface of Fruit Peels and Its Photocatalytic Activity.

The development of water treatment materials using environmentally friendly natural biomasses as substitutes plays an increasingly important role in environmental protection. Zeolitic imidazolate framework-8 (ZIF-8) is often used for the catalytic degradation of dye wastewater, but due to its small particle size, its disadvantage of easy agglomeration prevents it from being fully functional. Herein, we report an efficient method for synthesizing biomasses/ZIF-8 using four different fruit peels as carriers. ZIF-8 nanoparticles are in-situ grown uniformly on their surface. The Brunauer–Emmett–Teller surface area of shaddock peel/ZIF-8 was found to be 752.15 m2g–1. After catalytic activity comparison, the loose shaddock peel/ZIF-8 showed the fastest and most significant degradation efficiency of 94% in methylene blue aqueous solution and could be used multiple times through a simple washing process.

Poly(ethylene glycol)-Mediated Assembly of Vaccine Particles to Improve Stability and Immunogenicity.

We report the one-step assembly of vaccine particles by encapsulating ovalbumin (OVA) and cytosine-phosphate-guanine oligodeoxynucleotides (CpG) into poly(ethylene glycol) (PEG)-mediated zeolitic imidazolate framework-8 nanoparticles (OVA-CpG@ZIF-8 NPs), where PEG improves the stability and dispersity of ZIF-8 NPs and the NPs protect the encapsulated OVA and CpG to circumvent the cold chain issue. Compared with free OVA and OVA-encapsulated ZIF-8 (OVA@ZIF-8) NPs, OVA-CpG@ZIF-8 NPs can enhance antigen uptake, cross-presentation, dendritic cell (DC) maturation, production of specific antibody and cytokines, and CD4+ T and CD8+ T cell activation. More importantly, the vaccine particles retain their bioactivity against enzymatic degradation, elevated temperatures, and long-term storage at ambient temperature. The study highlights the importance of PEG-mediated ZIF-8 NPs as a vaccine delivery system for the promising application of effective and cold chain-independent vaccination against diseases.

Silica Capsules Templated from Metal-Organic Frameworks for Enzyme Immobilization and Catalysis.

Inspired by the unique biological microenvironments of eukaryotic cells, hollow capsules are promising to immobilize enzymes due to their advantages for physical protection and improved activity of enzymes. Herein, we report a facile method to fabricate silica (SiO2) capsules using zeolitic imidazole framework-8 nanoparticles (ZIF-8 NPs) as templates for enzyme immobilization and catalysis. Enzyme-encapsulated SiO2 capsules are obtained by encapsulation of enzymes in ZIF-8 NPs and subsequent coating of silica layers, followed by the removal of templates in a mild condition (i.e., ethylenediaminetetraacetic acid (EDTA) solution). The enzyme (i.e., horseradish peroxidase, HRP) activity in SiO2 capsules is improved more than 15 times compared to that of enzyme-loaded ZIF-8 NPs. Enzymes in SiO2 capsules maintain a high relative activity after being subjected to high temperature, enzymolysis, and recycling compared to free enzymes. In addition, multienzymes (e.g., glucose oxidase and HRP) can also be coencapsulated within SiO2 capsules to show a reaction with a high cascade catalytic efficacy. This work provides a versatile strategy for enzyme immobilization and protection with potential applications in biocatalysis.

Low doses of zeolitic imidazolate framework-8 nanoparticles alter the actin organization and contractility of vascular smooth muscle cells

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles have emerged as a promising platform for drug delivery and controlled release. Considering most ZIF-8 nanoparticle drug carriers are designed to be administered intravenously, and thus would directly contact vascular smooth muscle cells (VSMCs) in many circumstances, the potential interactions of ZIF-8 nanoparticles with VSMCs require investigation. Here, the effects of low doses of ZIF-8 nanoparticles on VSMC morphology, actin organization, and contractility are investigated. Two nanoscale imaging tools, atomic force microscopy, and direct stochastic optical reconstruction microscopy, show that even at the concentrations (12.5 and 25 µg/ml) that were deemed “safe” by conventional biochemical cell assays (MTT and LDH assays), ZIF-8 nanoparticles can still cause changes in cell morphology and actin cytoskeleton organization at the cell apical and basal surfaces. These cytoskeletal structural changes impair the contractility function of VSMCs in response to Angiotensin II, a classic vasoconstrictor. Based on intracellular zinc and actin polymerization assays, we conclude that the increased intracellular Zn2+ concentration due to the uptake and dissociation of ZIF-8 nanoparticles could cause the actin cytoskeleton dis-organization, as the elevated Zn2+ directly disrupts the actin assembly process, leading to altered actin organization such as branches and networks. Since the VSMC phenotype change and loss of contractility are fundamental to the development of atherosclerosis and related cardiovascular diseases, it is worth noting that these low doses of ZIF-8 nanoparticles administered intravenously could still be a safety concern in terms of cardiovascular risks. Moving forward, it is imperative to re-consider the “safe” nanoparticle dosages determined by biochemical cell assays alone, and take into account the impact of these nanoparticles on the biophysical characteristics of VSMCs, including changes in the actin cytoskeleton and cell morphology.

Zeolitic imidazolate framework nanoparticles loaded with gadolinium chelate as efficient T1 MRI contrast agent

Zeolitic imidazolate framework nanoparticles loaded with gadolinium chelate as efficient T1 MRI contrast agent

Zeolitic Imidazolate Framework-8 as promising nanoparticles for arsenic removal from aqueous solution

Removal of arsenic from water is an important task as it is harmful and toxic. In the current paper, Zeolitic Imidazolate Framework-8 nanoparticles were synthesised, and arsenic removal efficiency was examined from synthetic water. The optimum experiment value was developed by the Taguchi method, and the characterisation of nanoparticles was done by transmission electron microscope, which confirmed the particle. The result indicates that time was considered as an important factor in arsenic removal by ZIF-8 NPs followed by adsorbent dosage, stirring rate, temperature, and pH. The optimum conditions for arsenic removal by ZIF-8 NPs were found as time = 5 min, adsorbent dosage 0.06 g/l, Stirring = 400 RPM, temperature = 15°C, pH = 8. Regression analysis (R2 = 0.90) displayed a better outcome in predicted and experimental values. The outcome estimates that the adsorption of arsenic follows Langmuir isotherm for arsenic removal.

Biomineralized zeolitic imidazolate framework-8 nanoparticles enable polymerase/endonuclease synergetic amplification reaction in living cells for sensitive microRNA imaging.

In this work, we have implemented a polymerase and endonuclease synergetic amplification reaction in living cells for intracellular miRNA imaging by using biomineralized ZIF-8 NPs.

Rapid ultrasound-assisted synthesis of controllable Zn/Co-based zeolitic imidazolate framework nanoparticles for heterogeneous catalysis

While metal-organic frameworks (MOFs) exhibit excellent potential in extensive catalytic reactions, predictably synthesizing MOF nanoparticles (NPs) with desired and uniform sizes remains a great challenge. Here, a mild and efficient ultrasound-assisted synthetic method has been developed to prepare ZIF-8, ZIF-67, and Co/ZIF-8 with well-designed particle size and morphology. By adjusting the cobalt content doped into a heterometallic ZIF-8 structure, tunable particle sizes ranging from 35 nm to over 300 nm have been achieved, resulting from the differences in nucleation and growth rates of zinc and cobalt ZIFs. Impressively, this as-obtained bimetallic Zn/Co-ZIF shows hierarchical porous structure with modified physicochemical properties, leading to a change of nitrogen adsorption-desorption characteristics. In addition, when used as a heterogenous catalyst, the bimetallic Co-doped ZIF-8 is demonstrated to have both enhanced catalytic performance for the activation of peroxymonosulfate (PMS) in organic dye degradation compared to pure ZIF-8, as well as superior structural stability, when compared to monometallic ZIF-67. This work provides a novel strategy for the predictable design and controlled fabrication of bimetallic MOF nanostructures with desired structures and compositions.

Synthesis of nanoscale zeolitic imidazolate framework-8 (ZIF-8) using reverse micro-emulsion for Congo red adsorption

To enhance the removal of dyes from water, the adsorption capacity of an adsorbent can usually be increased via reducing its particle size and enlarging the specific area. To this end, a reverse micro-emulsion system was developed in this study using an ionic liquid ([C14MIm]Cl) to prepare nanoscale zeolitic imidazolate framework-8 (ZIF-8) material for Congo red (CR) anionic dye separation from water. The size and morphology of nano ZIF-8 synthesized under different conditions, including reaction time, the order of reactants addition, the molar ratio of water and [C14MIm]Cl and the concentration of reactants, were analyzed by dynamic light scattering (DLS) particle size analyzer and transmission electron microscope (TEM). The optimal synthesis conditions including reaction time of 60 min, the ratio of water and ionic liquid (ω0) of 60, and the concentrations of B1 and B2 solutions of 0.07 M and 0.28 M, were determined using the response surface method (RSM). Studies have shown that the reverse micro-emulsion system can effectively control the crystal size of ZIF-8 nanoparticles, with a uniform particle size distribution from 15 to 35 nm, smaller than that of the general ZIF-8 material prepared in the aqueous phase (100–200 nm). The specific surface area of the nano ZIF-8 particles synthesized under optimal synthesis conditions was 1477 m2/g. The synthesized nano ZIF-8 material removed Congo red (CR) dye from water efficiently by adsorption. Congo red adsorption on nano ZIF-8 was observed as a spontaneous endothermic adsorption process. The adsorption conformed to the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum predicted adsorption amount was 1339.8 mg/g at a temperature of 323 K. Analysis of adsorption mechanism shows that the adsorption of CR on nano ZIF-8 materials is mainly due to electrostatic interaction and physical attraction including hydrogen bonds and π-π bond interactions. This study further expands the application of reverse micro-emulsion method in nanoscale framework materials preparation.

Rationally designed rapamycin-encapsulated ZIF-8 nanosystem for overcoming chemotherapy resistance

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are widely reported as a pH-sensitive drug delivery carrier with high loading capacity for tumor therapy. However, the mechanism of intracellular corrosion of ZIF-8 and the corresponding biological effects especially for autophagy response have been rarely reported. Herein, the as-synthesized ZIF-8 was demonstrated to induce mTOR independent and pro-death autophagy. Interestingly, the autophagic process participated in the corrosion of ZIF-8. Subsequently, zinc ion release and the generation of reactive oxygen species due to its corrosion in the acidic compartments were directly responsible for tumor cell killing. In addition, ZIF-8 could sensitize tumor cells to chemotherapy by switching cytoprotective to death promoting autophagy induced by doxorubicin. The mTOR signaling pathway activation was demonstrated to restrict tumor chemotherapy efficiency. Hence, a combined platform rapamycin encapsulated zeolitic imidazolate frameworks (Rapa@ZIF-8) was constructed and demonstrated a more significant chemo-sensitized effect relative to ZIF-8 nanoparticles or rapamycin treatment alone. Lastly, the combined administration of Rapa@ZIF-8 and doxorubicin exhibited an outstanding synergistic antitumor effect without any obvious toxicity to the major organs of mice. Collectively, the optimized nanoplatform, Rapa@ZIF-8, provides a proof of concept for intentionally interfering mTOR pathway and utilizing the switch of survival-to death-promoting autophagy for adjunct chemotherapy.

ZIF-8-Modified Multifunctional Bone-Adhesive Hydrogels Promoting Angiogenesis and Osteogenesis for Bone Regeneration.

Designing bone adhesives with adhesiveness, antideformation, biocompatibility, and biofunctional effects has great practical significance for bone defect reconstructive treatment, especially for bone graft repair surgery. Here, we designed zeolitic imidazolate framework-8 nanoparticle (ZIF-8 NP)-modified catechol-chitosan (CA-CS) multifunctional hydrogels (CA-CS/Z) to stabilize the bone graft environment, ensure blood supply, promote osteogenic differentiation, and accelerate bone reconstruction. Characterizations confirmed the successful synthesis of CA-CS/Z hydrogels. Hydrogels exhibited advanced rheological properties, reliable mechanical strength, and excellent adhesion for clinical applications. Based on excellent biocompatibility, it could enhance paracrine of the vascular endothelial growth factor (VEGF) in rat bone marrow mesenchymal stem cells (rBMSCs) to ensure blood supply reconstruction in bone defect areas. Furthermore, the ZIF-8 NPs released from the hydrogels could also up-regulate the production and secretion of alkaline phosphatase, collagen 1, and osteocalcin, promoting the osteogenic differentiation of rBMSCs. In addition, the antibacterial properties of CA-CS/Z could also be observed. In vivo experiments further provided a powerful proof that CA-CS/Z promoted vascularized osteogenesis in wound areas by stabilizing bone graft materials and greatly accelerated the speed and healing of bone reconstruction. These results indicate the promising potential of CA-CS/Z hydrogels with promoting implantation stability, angiogenesis, and osteogenesis for bone regeneration applications.

Strengthening CO2 dissolution with zeolitic imidazolate framework-8 nanoparticles to improve microalgal growth in a horizontal tubular photobioreactor

Low dissolution of CO2 in closed tubular photobioreactors results in insufficient carbon source supply, and often limits microalgae growth. An optimized ZIF8-SE medium containing zeolitic imidazolate framework-8 (ZIF-8) nanoparticles was developed for strengthening CO2 mass transfer in the photobioreactor, which improved CO2 dissolution to increase microalgal biomass yield under 15% CO2. The CO2 mass transfer coefficient markedly increased from 1.82 to 3.85, leading to an increased dissolved inorganic carbon concentration. Meanwhile, microalgae biomass accumulation with 0.01 mmol/L ZIF-8 nanoparticles was 25.5% higher than that without ZIF-8 nanoparticles. Furthermore, the average cell size decreased from 2.61 to 2.38 μm and the cell fractal dimension increased from 1.38 to 1.56 when ZIF-8 nanoparticle concentration increased from 0 to 0.2 mmol/L, indicating that potential toxicity might occurred with excess ZIF-8 nanoparticles. Reutilization of ZIF-8 nanoparticles in the recycled culture medium improved microalgal growth by 23%, which was similar to the promotion of fresh ZIF8-SE medium. This new finding provides a new strategy to improve CO2 mass transfer in the horizontal tubular photobioreactor, which makes it a feasible platform for CO2 capture and utilization.