Toxicity and photosynthetic inhibition of metal-organic framework MOF-199 to pea seedlings

Effects of zeolite imidazole frameworks on rice seedlings (Oryza sativa L.): Phytotoxicity, transformation, and bioaccumulation

Zeolite imidazole frameworks (ZIFs), a class of the metal organic framework, have been extensively studied in environmental applications. However, their environmental fate and potential ecological impact on plants remain unknown. Here, we investigated the phytotoxicity, transformation, and bioaccumulation processes of two typical ZIFs (ZIF-8 and ZIF-67) in rice (Oryza sativa L.) under hydroponic conditions. ZIF-8 and ZIF-67 in the concentration of 50 mg/L decreased root and shoot dry weight maximally by 55.2% and 27.5%, 53.5% and 37.5%, respectively. The scanning electron microscopy (SEM) imaging combined with X-ray diffraction (XRD) patterns revealed that ZIFs on the root surface gradually collapsed and transformed into nanosheets with increasing cultivation time. The fluorescein isothiocyanate (FITC) labeled ZIFs were applied to trace the uptake and translocation of ZIFs in rice. The results demonstrated that the transformed ZIFs were mainly distributed in the intercellular spaces of rice root, while they cannot be transported to culms and leaves. Even so, the Co and Zn contents of rice roots and shoots in the ZIFs treated groups were increased by 1145% and 1259%, 145% and 259%, respectively, compared with the control groups. These findings suggested that the phytotoxicity of ZIFs are primarily attributed to the transformed ZIFs and to a less extent, the metal ions and their ligands, and they were internalized by rice root and increased the Co and Zn contents of shoots. This study reported the transformation of ZIFs and their biological effectiveness in rice, highlighting the potential environmental hazards and risks of ZIFs to crop plants.

Harnessing plant-beneficial bacterial encapsulation: A sustainable strategy for facilitating cadmium bioaccumulation in Medicago sativa

Plant-beneficial bacteria (PBB) have emerged as a promising approach for assisting phytoremediation of heavy metal (HM)-contaminated soils. However, their colonization efficiency is often challenged by complex soil environments. In this study, we screened one rhizobacterium (Klebsiella variicola Y38) and one endophytic bacterium (Serratia surfactantfaciens Y15) isolated from HM-contaminated soils and plants for their high resistance to Cd and strong growth-promoting abilities. These strains were encapsulated individually or in combination with alginate and applied with Medicago sativa in Cd-contaminated soil pot experiments. The effectiveness of different bacterial formulations in promoting plant growth and enhancing Cd bioconcentration in M. sativa was evaluated. Results showed that PBB application enhanced plant growth and antioxidant capacity while reducing oxidative damage. Encapsulated formulations outperformed unencapsulated ones, with combined formulations yielding superior results to individual applications. Quantitative PCR indicated enhanced PBB colonization in Cd-contaminated soils with alginate encapsulation, potentially explaining the higher efficacy of alginate-encapsulated PBB. Additionally, the bacterial agents modified Cd speciation in soils, resulting in increased Cd bioaccumulation in M. sativa by 217-337 %. The alginate-encapsulated mixed bacterial agent demonstrated optimal effectiveness, increasing the Cd transfer coefficient by 3.2-fold. Structural equation modeling and correlation analysis elucidated that K. variicola Y38 promoted Cd bioaccumulation in M. sativa roots by reducing oxidative damage and enhancing root growth, while S. surfactantfaciens Y15 facilitated Cd translocation to shoots, promoting shoot growth. The combined application of these bacteria leveraged the benefits of both strains. These findings contribute to diversifying strategies for effectively and sustainably remediating Cd-contaminated soils, while laying a foundation for future investigations into bacteria-assisted phytoremediation.

Raman spectroscopic quantification of graphene oxide in soil: Transport, surficial enrichment and environmental effects

The transport and retention data in environmental media are indispensable for the hazard evaluations of graphene materials. Due to the complexity of soil, the transport of graphene is hard to quantify without isotope labeling. Herein, we developed 2D Raman mapping as a label-free technique to quantify graphene oxide (GO) in soil. After pre-treatment by hydrazine hydrate to quench its fluorescence, the quantification of GO in soil was achieved in the range of 0.1-1000 mg/L by measuring the average G-band intensity. In column transport experiment, the transport and retention of GO in soil depended on the solution chemistry. Lower pH and higher ionic strength hindered the transport of GO. In particular, Ca2+ showed the most obvious retardation on the transport of GO. GO enriched in the surficial soil layer by several folds of the initial concentrations, and higher GO concentration led to more surficial enrichment. The sowing manner of seeds affected the soil enrichment of GO, too. The surficial enrichment of GO reduced its direct contact with seedling roots, resulting in the alleviation of GO toxicity. Our results provided a facile method to study the environmental behaviors of graphene and highlighted the crucial impacts of environmental media on the graphene toxicity.

Reduced graphene oxide promotes the biodegradation of sulfamethoxazole by white-rot fungus Phanerochaete chrysosporium under cadmium stress

The biodegradation of antibiotics in aquatic environment is consistently impeded by the widespread presence of heavy metals, necessitating urgent measures to mitigate or eliminate this environmental stress. This work investigated the degradation of sulfamethoxazole (SMX) by the white-rot fungus Phanerochaete chrysosporium (WRF) under heavy metal cadmium ion (Cd2+) stress, with a focus on the protective effects of reduced graphene oxide (RGO). The pseudo-first-order rate constant and removal efficiency of 5 mg/L SMX in 48 h by WRF decrease from 0.208 h-1 and 55.6% to 0.08 h-1 and 28.6% at 16 mg/L of Cd2+, while these values recover to 0.297 h-1 and 72.8% by supplementing RGO. The results demonstrate that RGO, possessing excellent biocompatibility, effectively safeguard the mycelial structure of WRF against Cd2+ stress and provide protection against oxidative damage to WRF. Simultaneously, the production of manganese peroxidase (MnP) by WRF decreases to 38.285 U/L in the presence of 24 mg/L Cd2+, whereas it recovers to 328.51 U/L upon the supplement of RGO. RGO can induce oxidative stress in WRF, thereby stimulating the secretion of laccase (Lac) and MnP to enhance the SMX degradation. The mechanism discovered in this study provides a new strategy to mitigate heavy metal stress encountered by WRF during antibiotic degradation.

Dose-Dependent Effect on Plant Growth of Exposure to Metal-Organic Framework MIL-101(Cr)

With the increasing use of metal-organic frameworks (MOFs), they will inevitably enter the environment intentionally or unintentionally. However, the effects of MOFs on plant growth are poorly understood. Here, we investigated the effects of exposure of the rhizosphere to MOFs on plant growth. MIL-101(Cr) was selected as a research model due to its commercial availability and wide use. Soybean plants at the two-leaf stage were subjected to various durations (1-7 days) and concentrations (0-1000 mg/L) of exposure in hydroculture with a control group treated with ultrapure water. We found that MIL-101(Cr) had a positive effect on soybean growth at a lower dose (i.e., 200 mg/L); however, at higher doses (i.e., 500 and 1000 mg/L), it exhibited significant toxicity to plant growth, which is evidenced by leaf damage. To investigate the mechanism of this effect, we used Cr as an indicator to quantify, track, and image MIL-101(Cr) in the plant with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Results indicated that MIL-101(Cr) primarily accumulated in the cortex of roots (up to 40 times higher than that in stems), with limited translocation to stems and negligible presence in leaves and cotyledons. In addition, metabolomic analysis of soybeans indicated that low-dose MIL-101(Cr) could increase the sucrose content of soybean roots to promote plant growth, while a high dose could induce lipid oxidation in roots. This study provides valuable insights into the ecological toxicology of MOFs and underscores the importance of assessing their environmental impact for sustainable agricultural practices.

Phytotoxicity of metal-organic framework MOF-74(Co) nanoparticles to pea seedlings

Metal-organic framework (MOF) materials have unique structure and fantastic properties for wide-ranging applications. Pilot studies highlighted the toxicity and potential threats of MOF materials to the environment. In this study, we revealed the phytotoxicity of MOF-74(Co) nanoparticles (NPs) and their inhibitory effects on the photosynthesis of pea seedlings (Pisum sativum L.). MOF-74(Co) NPs have limited influences on the germination of pea seeds, but distinct environmental effects of MOF-74(Co) NPs were found in pea seedlings. The root length of pea seedlings, fresh weight and dry weight decreased by 50.0%, 29.2% and 36.4%, respectively, compared with the control group, when the material concentration was greater than 100 mg L-1. The net photosynthetic rate decreased by 48% and the intercellular CO2 concentration increased by 183% upon exposure to MOF-74(Co) NPs. Mechanistically, MOF-74(Co) exposure led to Co uptake in pea seedlings; the increases were 223% for the root, 267% for the stem and 6562% for the leaves, respectively, when the MOF-74(Co) NP concentration was 10 mg L-1. The released Co ions from MOF-74(Co) NPs caused oxidative damage to leaves and induced damage to the acceptor side of photosynthesis system II. Our results indicated that the environmental toxicity of MOF materials was largely regulated by the metal centers. MOF materials with nontoxic metal elements are desirable for future applications.

Effect of HKUST-1 metal-organic framework in root and shoot systems, as well as seed germination

The seed germination, as well as root and shoot growth effect of HKUST-1 MOF, and its derived linear polymer ([Cu2(OH)(BTC)(H2O)]n·2nH2O) were herein examined. These effects were studied for seven higher plant species: sweet corn (Zea mays L.), black bean (Phaseolus vulgaris L.), tomato (Solanum lycopersicum L.), lettuce (Lactuca sativa L.), celosia (Celosia argentea L.), Aztec marigold (Tagetes erecta L.), and gypsophila (Gypsophila paniculata L.). The studied concentrations of MOFs were 10, 100, 500, or 1000 mg/L, enhancing the percentage of germination and growth of plants in most species. In general, the growth of the root is lower compared to the controls due to the capacity of the MOF to adsorb water and provide micronutrients such as C, O, and Cu, acting as a reserve for the plant. Shoot system growths are more pronounced with HKUST-1 compared with control, and linear polymer, due to the 3D structure adsorbs major water contents. It was found that all studied species are tolerant not only to Cu released from the material, but more evident to Cu structured in MOFs, and this occurs at high concentrations compared to many other systems. Finally, copper fixation was not present, studied by EDX mapping, banning the possibility of metallic phytotoxicity to the tested cultivars.

Orange peel-derived carbon dots/Cu-MOF nanohybrid for fluorescence determination of l-ascorbic acid and Fe3. Anal Chim Acta 2024;1287:342066. [PMID: 38182373 DOI: 10.1016/j.aca.2023.342066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Recycling and reuse of biomass waste in synthesis of nanomaterials have recently received much attention as an effective solution for environmental protection and sustainable development. Herein, nitrogen-doped carbon dots (N-CDs) with blue emission were synthesized from the orange peels as a precursor through a simple hydrothermal method and then, modified with ethylenediamine tetraacetic acid (N-CD@EDTA). The N-CD@EDTA was embedded as a fluorophore in Cu-based metal-organic framework (MOF-199) structure (N-CD@EDTA/MOF-199) to construct fluorescence sensor toward l-ascorbic acid (L-AA) determination. The N-CD@EDTA/MOF-199 nanohybrid significantly and selectively turned on toward L-AA determination during the fluorimetric experiments. Under optimal conditions, the probe showed a suitable linear response in the concentration range of 10 nM-100 μM with a low limit of detection (LOD) of 8.6 nM and high sensitivity of 0.201 μM-1. The possible mechanism of recognition and adsorption, including the reduction of Cu 2+ nodes in the MOF-199 structure in the presence of L-AA and the release of trapped N-CD@EDTA into the solution, was explored. Moreover, the N-CD@EDTA/MOF-199/L-AA (100 μM) system was further applied as a fluorescent "on-off" sensor for Fe3+ determination with a LOD of 1.15 μM. The proposed probe was successfully used in orange juice and water samples to determine L-AA and Fe3+ with satisfactory recovery, which displays the promising capability of sensor in real samples. The recoveries obtained by suggested method are consistent with that obtained from high performance liquid chromatography (HPLC) and atomic absorption spectroscopy which confirm the favorable characteristic of the sensor for accurate determination of L-AA and Fe3+ in practical applications.

Enhanced Thermal Decomposition and Safety of Spherical CL-20@MOF-199 Composites via Micro-Nanostructured Self-Assembly Regulation

The characteristics of high burning rate, high energy output, and low pressure exponent have always been the focus of development in the field of composite solid rocket propellants. In this paper, a metal-organic framework (MOF-199) compound is introduced to prepare micro-nanospherical CL-20@MOF-199 composites via the spray-drying self-assembly technique to reach the above goals. MOF-199, which acts as an attractive combustion catalyst and a safety regulator, is uniformly coated on the surface of CL-20 with close interface contact between particles, effectively accelerating the thermal decomposition of CL-20 and ensuring safety performance. The average noncovalent interaction (aNCI) analysis illustrates that there are strong C-H···O hydrogen bonds and van der Waals interaction between CL-20 and MOF-199 molecules, greatly enhancing the effect of interparticle assembly. The effects of different contents of MOF-199 on the thermal, safety, and energy properties of CL-20 were discussed. The thermal analysis demonstrates that MOF-199 has a significant thermal catalytic effect on CL-20, with an advanced peak temperature of thermal decomposition of 14.2 °C and a reduced activation energy barrier of 34.2 kJ·mol-1, mainly benefitting from more exposed catalytic active sites and close interface contact. In addition, CL-20@MOF-199 composites exhibit decreased mechanical sensitivity (IS: 21-40 cm, FS: 80-240 N) and excellent energy performance. This work clearly demonstrates that MOF-199 is both a superior combustion catalyst and a good safety buffer for CL-20, and it opens new potential for further applications of CL-20 in composite solid propellants.

Determination of Lincomycin in Milk Using Cu-Based Metal-Organic Framework Adsorbent and Liquid Chromatography-Tandem Mass Spectrometry

Antibiotic drug residues can adversely affect the human body. Lincomycin is a common veterinary drug that can form residues in foods of animal origin. However, the detection of trace residue levels of lincomycin residues in real samples is challenging. Here, a simple solid phase extraction (SPE) method was developed for the enrichment of lincomycin from cow milk samples before its detection by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The adsorbent used in the SPE was a Cu-based metal-organic framework (Cu-MOF) prepared by the solvothermal synthesis approach. The prepared MOFs were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential thermogravimetric analysis (TG-DTA), and N2 adsorption-desorption experiments. The adsorption capacity (adsorption equilibrium, extraction time, pH), and elution solvent parameters were investigated. Under the optimized conditions of the HPLC-MS/MS method, lincomycin was detected in the linear range of 10-200 g/L with a detection limit of 0.013 ng/mL. Commercial milk samples were spiked with lincomycin, and a recovery rate between 92.3% and 97.2% was achieved. Therefore, the current method can be successfully applied for the enrichment and determination of lincomycin from milk samples.

Organic ligands regulate the environmental impacts of metal-organic frameworks on nitrogen-fixing bacterium Azotobacter vinelandii

Metal-organic frameworks (MOFs) are rapidly developed materials with fantastic properties and wide applications. The increasing studies highlighted the potential threats of MOF materials to the environment. Comparing to the limited species of metal elements, the organic ligands have much higher diversity, but the influence of organic ligands on the environmental impacts of MOFs has not been revealed. Herein, we synthesized three Cu-MOFs with different organic ligands, namely Cu-BDC (1,4-terephthalic acid), Cu-IM (imidazole) and Cu-TATB (2,4,6-tris(4-carboxyphenyl)- 1,3,5-triazine), and evaluated their environmental toxicity to the nitrogen-fixing bacterium Azotobacter vinelandii. Cu-BDC inhibited the bacterial growth at lower concentrations than Cu-IM and Cu-TATB. The transcriptomes suggested the changes of membrane components by Cu-MOFs, consistent with the membrane leakage and cell wall damages. Cu-MOFs inhibited the nitrogen fixation activity through energy metabolism disturbance according to Gene Ontology functional annotation of ATP binding, Ca²⁺Mg²⁺-ATPase activity and ATP content. Only Cu-IM lowered the nitrogen fixation related nif genes, and affected the ribosome, purine metabolism and oxidative phosphorylation pathways. Otherwise, Cu-BDC and Cu-TATB mainly affected the flagellar assemblies and bacterial chemotaxis pathways. Our results collectively indicated that organic ligands regulated the environmental toxicity of MOFs through different metabolism pathways.

Nano-based smart formulations: A potential solution to the hazardous effects of pesticide on the environment

Inefficient usage, overdose, and post-application losses of conventional pesticides have resulted in severe ecological and environmental issues, such as pesticide resistance, environmental contamination, and soil degradation. Advances in nano-based smart formulations are promising novel methods to decrease the hazardous impacts of pesticide on the environment. In light of the lack of a systematic and critical summary of these aspects, this work has been structured to critically assess the roles and specific mechanisms of smart nanoformulations (NFs) in mitigating the adverse impacts of pesticide on the environment, along with an evaluation of their final environmental fate, safety, and application prospects. Our study provides a novel perspective for a better understanding of the potential functions of smart NFs in reducing environmental pollution. Additionally, this study offers meaningful information for the safe and effective use of these nanoproducts in field applications in the near future.

The accumulation and toxicity of ZIF-8 nanoparticles in Corbicula fluminea

Metal-organic frameworks (MOFs) are promising new materials that have been intensively studied and possibly applied to various environmental remediation. However, little is known about the fate and risk of MOFs to living organisms in the water environment. Here, the toxic effects of ZIF-8 nanoparticles (NPs) on benthic organisms were confirmed by sub-chronic toxicity experiments (7 and 14 days) using Corbicula fluminea as the model organism. With exposure doses ranging from 0 to 50 mg/L, ZIF-8 NPs induced oxidative stress behaviors similar to the hormesis effect in the tissues of C. fluminea. The oxidative stress induced by ZIF-8 NPs and the released Zn²⁺ was the crucial cause of the toxic effects. Besides, we also found that the ZIF-8 NPs and dissolved Zn²⁺ may result in different mechanisms of toxicity and accumulation depending on the dosages. The Zn²⁺ release rate of ZIF-8 NPs was high at low dosages, leading to a higher proportion of Zn²⁺ taken up by C. fluminea than the particulate ZIF-8. Conversely, at high dosages, C. fluminea mainly ingested the ZIF-8 NPs and resulted in increased mortality. The results have important implications for understanding the fate and biological effects of ZIF-8 in natural aquatic environments.

Factors affecting the toxicity and oxidative stress of layered double hydroxide-based nanomaterials in freshwater algae

Layered double hydroxide (LDH) nanomaterials are utilized extensively in numerous fields because of their distinctive structural properties. It is critical to understand the environmental behavior and toxicological effects of LDHs to address potential concerns caused by their release into the environment. In this work, the toxicological effects of two typical LDHs (Mg-Al-LDH and Zn-Al-LDH) on freshwater green algae (Scenedesmus obliquus) and the main affecting factors were examined. The Zn-Al-LDH exhibited a stronger growth inhibition toxicity than the Mg-Al-LDH in terms of median effect concentration. This toxicity difference was connected to the stability of particle dispersion in water and the metallic composition of LDHs. The contribution of the dissolved metal ions to the overall toxicity of the LDHs was lower than that of their particulate forms. Moreover, the joint toxic action of different dissolved metal ions in each LDH belonged to additive effects. The Mg-Al-LDH induced a stronger oxidative stress effect in algal cells than the Zn-Al-LDH, and mitochondrion was the main site of LDH-induced production of reactive oxygen species. Scanning electron microscope observation indicated that both LDHs caused severe damage to the algal cell surface. At environmentally relevant concentrations, the LDHs exhibited joint toxic actions with two co-occurring contaminants (oxytetracycline and nano-titanium dioxide) on S. obliquus in an additive manner mainly. These findings emphasize the impacts of the intrinsic nature of LDHs, the aqueous stability of LDHs, and other environmental contaminants on their ecotoxicological effects.

Constructing functional metal-organic frameworks by ligand design for environmental applications

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

Synthesis and potential applications of cyclodextrin-based metal-organic frameworks: a review

Metal-organic frameworks are porous polymeric materials formed by linking metal ions with organic bridging ligands. Metal-organic frameworks are used as sensors, catalysts for organic transformations, biomass conversion, photovoltaics, electrochemical applications, gas storage and separation, and photocatalysis. Nonetheless, many actual metal-organic frameworks present limitations such as toxicity of preparation reagents and components, which make frameworks unusable for food and pharmaceutical applications. Here, we review the structure, synthesis and properties of cyclodextrin-based metal-organic frameworks that could be used in bioapplications. Synthetic methods include vapor diffusion, microwave-assisted, hydro/solvothermal, and ultrasound techniques. The vapor diffusion method can produce cyclodextrin-based metal-organic framework crystals with particle sizes ranging from 200 nm to 400 μm. Applications comprise food packaging, drug delivery, sensors, adsorbents, gas separation, and membranes. Cyclodextrin-based metal-organic frameworks showed loading efficacy of the bioactive compounds ranging from 3.29 to 97.80%.

Low Toxicity of Metal-Organic Framework MOF-74(Co) Nano-Particles In Vitro and In Vivo

With the rapid development of metal-organic frameworks (MOF), the toxicity and environmental safety of MOF materials should be thoroughly investigated. The behaviors and bio-effects of MOF materials after oral exposure are largely unknown. In this study, we performed a pilot toxicity evaluation of MOF-74(Co) nanoparticles (NPs) both in vitro and in vivo. The cell viability and cell cycle were monitored after LO2 cells were incubated with MOF-74(Co). The Co contents, bodyweight, serum biochemistry, histopathological changes, and oxidative stress parameters were measured after oral exposure to MOF-74(Co) NPs in mice. LO2 cells showed viability loss at 100 mg/L. The cell cycle arrest was more sensitive, which was observed even at 12.5 mg/L. MOF-74(Co) NPs led to a significant accumulation of Co in the liver and kidneys. No bodyweight loss was observed and the serum biochemical index was mainly unchanged. Except for slight inflammation, the histopathological images of the liver and kidneys after oral exposure to MOF-74(Co) NPs were normal compared to the control. Meaningful oxidative stress was found in the liver and kidneys. The results collectively indicated the low toxicity of MOF-74(Co) NPs after oral exposure in mice.

Phytotoxicity of VO2 nanoparticles with different sizes to pea seedlings

Vanadium dioxide nanoparticles (VO2 NPs) have been massively produced due to their excellent metal-insulator transition characteristics for various applications. Pilot studies indicated the toxicity of VO2 NPs to bacteria and mammalian cells, but the environmental hazards of VO2 NPs to plants have been unrevealed to date. In this study, we reported the inhibitive effects of VO2 NPs to the growth and photosynthesis of pea seedlings. Laboratory synthesized monoclinic VO2 NPs (N-VO2), commercial nanosized VO2 NPs (S-VO2), and commercial microsized VO2 particles (M-VO2) were carefully characterized for environmental toxicity evaluations. VO2 particles were supplemented to culture medium for seed germination and seedling growth. All three VO2 samples did not affect the germination rates of pee seeds, while serious growth inhibition of pea seedlings was observed at 10 mg/L for S-VO2 and N-VO2, and 100 mg/L for M-VO2. VO2 particles had no impact on the chlorophyll contents, but the photosynthesis of leaf was significantly decreased following the consequence of N-VO2 > S-VO2 > M-VO2. The inhibition of photosynthesis was attributed to the damage of acceptor side of photosystem II by VO2 particles at high concentrations. Abundant bioaccumulations of vanadium in roots aroused oxidative damage and changed the root structure. Our results collectively indicated that the phytotoxicity of VO2 NPs was related to the concentration, size and crystalline degree.

Toxicity and activity inhibition of metal-organic framework MOF-199 to nitrogen-fixing bacterium Azotobacter vinelandii

Metal-organic framework (MOF) materials with fantastic properties have found important applications in various areas. Learning the lessons from plastics and microplastics, it is urgent to investigate the environmental impacts of emerging materials to avoid potential pollution. However, the environmental toxicity and risks of MOF materials are seldom reported. Herein, we studied the toxicity and activity inhibition of MOF-199 to nitrogen-fixing bacterium Azotobacter vinelandii. MOF-199 significantly suppressed the growth of A. vinelandii and led to cell death at 40 mg/L. MOF-199 penetrated the cell wall and induced the shrinking of bacterial cells. MOF-199 reduced the nitrogen fixation activity of A. vinelandii at 40 mg/L by decreasing the gene nifH levels and inhibiting the Ca²⁺Mg²⁺-ATPase activity, which was further confirmed by the changes in oxidative phosphorylation related genes. Complete growth inhibition and activity loss of A. vinelandii occurred at 60 mg/L of MOF-199. The toxicological mechanism of MOF-199 to A. vinelandii was assigned to the oxidative stress, which occurred at 20 mg/L and higher. Both Cu²⁺ release and particulates themselves contributed to the toxicity of MOF-199 to A. vinelandii. These findings highlighted the environmental hazards and risks of MOF materials to nitrogen-fixing bacteria and nitrogen fixation in the biogeochemical cycle.

Environmental decomposition and remodeled phytotoxicity of framework-based nanomaterials

Zeolitic imidazole frameworks (ZIFs) have attracted a considerable amount of attention for use in environmental applications (e.g., pollutant adsorption and photocatalysis in water treatments). The environmental stability and toxicity of ZIFs are key prerequisites for their practical applications, but information about these factors is largely lacking. The present work finds that pristine ZIFs (ZIF-8 and ZIF-67) photodegrade from frame structures into two-dimensional nanosheets and are oxidized to zinc carbonate (ZIF-8) and Co₃O₄ (ZIF-67) under visible-light irradiation. The photoinduced electrons, holes and free radicals promote dissolution of the metal cores and organic ligands, leading to collapse of the frame structure. The photodegradation of ZIF-8 alleviates developmental inhibition, oxidative stress, plasmolysis, and photosynthetic toxicity, while the photodegradation of ZIF-67 aggravates nanotoxicity. The integration of metabolomics and transcriptomics analysis reveals that unsaturated fatty acid biosynthesis and metal ion-binding transcription contribute to the altered toxicity of ZIF photodegradation. These findings highlight the roles of photodegradation in structural transformation and alteration of the toxicity of ZIFs, alarming the study of pristine metal-organic frameworks (MOFs).

Facile synthesis of Cu N-lauroyl sarcosinate nanozymes with laccase-mimicking activity and identification of toxicity effects for C. elegans

Toxicity assessment of Caenorhabditis elegans Cu-Ls Nz with laccase-like activity.

Preparation of chitosan crosslinked with metal-organic framework (MOF-199)@aminated graphene oxide aerogel for the adsorption of formaldehyde gas and methyl orange

Chitosan crosslinked with metal-organic framework (MOF-199)@aminated graphene oxide aerogel (MOF-199@AFGO/CS) were prepared to adsorb formaldehyde and methyl orange. The prepared MOF-199@AFGO/CS aerogel was well characterized via SEM, EDX, FT-IR, XRD and XPS to reveal the microstructure and composition. Besides, the mechanical property and the stability of MOF-199@AFGO/CS aerogel were investigated. The results showed that MOF-199@AFGO/CS aerogel had good stability in water, compression resilience and thermostability. The study on the ability to adsorb formaldehyde gas and methyl orange showed that the adsorption capacity of MOF-199@AFGO/CS aerogel was related to the pore size and the surface functional groups of MOF-199@AFGO/CS aerogel. When the pore size is moderate, as the amino group and MOF-199 on the aerogel increased, the adsorption capacity of formaldehyde gas (197.89 mg/g) and methyl orange (412 mg/g) can reach the maximum. Furthermore, the adsorption process at equilibrium followed the Freundlich isotherm model. The kinetic behavior was well fitted by the pseudo-second-order model, indicating chemisorption as the rate-determining step. This work can provide a reliable basis for the adsorbent to remove pollutants in different forms at the same time, and has potential application in simultaneously adsorbing liquid pollutants and gas pollutants.

Persistence and Recovery of ZIF-8 and ZIF-67 Phytotoxicity

Zeolitic imidazolate frameworks (ZIFs) have been developed quickly and have attracted considerable attention for use in the detection and removal of various pollutants. Understanding the environmental risks of ZIFs is a prerequisite to their safe application by industry and new chemical registration by governments; however, the persistence and recovery of toxicity induced by ZIFs remain largely unclear. This study finds that typical ZIFs (e.g., ZIF-8 and ZIF-67) at a concentration of 0.01-1 mg/L induce significant algal growth inhibition, plasmolysis, membrane permeability, chloroplast damage, and chlorophyll biosynthesis, and the above alterations are recoverable. Unexpectedly, a persistent decrease in reactive oxygen species (ROS) is observed due to the quenching of hydroxyl free radicals. The adverse effects of ZIF-8 are weak and easily alleviated compared with those of ZIF-67. ZIF-8 is internalized mainly by caveolae-mediated endocytosis, while ZIF-67 is internalized mainly by clathrin-mediated endocytosis. Omics studies reveal that the downregulation of mRNA associated with oxidative phosphorylation and the inhibition of chlorophyll and adenosine triphosphate (ATP) synthesis in mitochondria are related to the persistence of phytotoxicity. These findings highlight the phenomena and mechanisms of the persistence and recovery of phytotoxicity, indicating the need to reconsider the environmental risk assessments of ZIFs.

A molecularly imprinted polymer based on MOF and deep eutectic solvent for selective recognition and adsorption of bovine hemoglobin

In this study, a novel kind of imprinted polymers based on metal-organic frameworks (MOF@DES-MIPs) was prepared, using bovine hemoglobin (BHb) as template molecules and deep eutectic solvents (DES) as functional monomers for selective recognition and adsorption of BHb. MOF were used as the substrates to improve the accessibility of imprinted sites and DES as the functional monomers to produce different forces for BHb to help the formation of imprinted sites. Imprinted polymer films were taken to provide analyte selectivity. The MOF@DES-MIPs prepared were characterized and evaluated by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectrometer. We also investigated the influences of BHb concentration and adsorption time on the performance of MOF@DES-MIPs. The maximal adsorption capacity of MOF@DES-MIPs to BHb reached 151.28 mg g^-1, and the MOF@DES-MIPs showed good selectivity and fast adsorption equilibrium, which might offer a novel method for the preparation and research of molecularly imprinted polymers of biomacromolecules. In addition, MOF@DES-MIPs were successfully applied in the selective recognition of BHb from a real bovine blood sample. Graphical abstract.