Size-dependent acute toxicity and oxidative damage caused by cobalt-based framework (ZIF-67) to Photobacterium phosphoreum

Unleashing the antibacterial potential of ZIFs and their derivatives: mechanistic insights

Antibiotic resistance presents an alarming threat to global health, with bacterial infections now ranking among the leading causes of mortality. To address this escalating challenge, strategies such as antibiotic stewardship, development of antimicrobial therapies, and exploration of alternative treatment modalities are imperative. Metal-organic frameworks (MOFs), acclaimed for their outstanding biocompatibility and in vivo biodegradability, are promising avenues for the synthesis of novel antibiotic agents under mild conditions. Among these, zeolitic imidazolate frameworks (ZIFs), a remarkable subclass of MOFs, have emerged as potent antibacterial materials; the efficacy of which stems from their porous structure, metal ion content, and tunable functionalized groups. This could be further enhanced by incorporating or encapsulating metal ions, such as Cu, Fe, Ti, Ag, and others. This perspective aims to underscore the potential of ZIFs as antibacterial agents and their underlying mechanisms including the release of metal ions, generation of reactive oxygen species (ROS), disruption of bacterial cell walls, and synergistic interactions with other antibacterial agents. These attributes position ZIFs as promising candidates for advanced applications in combating bacterial infections. Furthermore, we propose a novel approach for synthesizing ZIFs and their derivatives, demonstrating exceptional antibacterial efficacy against Escherichia coli and Staphylococcus aureus. By highlighting the benefits of ZIFs and their derivatives as antibacterial agents, this perspective emphasizes their potential to address the critical challenge of antibiotic resistance.

Highly sensitive and selective detection of SARS-CoV-2 spike protein S1 using optically-active nanocomposite-coated melt-blown masks

Detection of viruses, including coronavirus (SARS-CoV-2), via facile, fast, and optical methods is highly important to control pandemics. In this regard, optically-active nanomaterials and nanoparticles (NPs) are a wise choice due to their long-term stability, ease of functionalization, and modifications. In this work, a nanocomposite based on NiFe layered double hydroxide (LDH) and ZIF-67 metal-organic framework (MOF) was designed and synthesized, and decorated on the surface of the melt-blown mask. The developed nanocomposite has a fluorescence emission at 625 nm. The selectivity of the nanocomposite towards the SARS-CoV-2 spike protein S1 was increased by adding CuO NPs. The limit of detection (LOD) of 1.5 nM and 24.5 nM against SARS-CoV-2 spike protein S1 was recorded by NiFe LDH@ZIF-67@CuO nanocomposite, and NiFe LDH@ZIF-67@CuO decorated on the surface of melt-blown. Also, in the presence of potential competitors and other types of pathogens, including Influenza virus types A and B, Staphylococcus aureus bacteria, and even cations/macromolecules, the fluorescence intensity changes had more than 40 % difference.

Revealing the synergistic impacts of ZIF-8 and copper co-exposure on zebrafish behavior, tissue damage, and intestine microbial community

The application of metal-organic frameworks (MOFs) has garnered significant attention in contemporary research. However, the impacts of MOFs on aquatic environments remain largely unclear. This study revealed that the water stability of ZIF-8 is influenced by its concentration, with lower concentrations resulting in higher percentages of Zn2+ release. At 10 mg/L, ZIF-8 significantly reduced zebrafish locomotor activity, with total swimming distance decreasing by approximately 40.5%. Oxidative stress and neurotoxicity markers, reactive oxygen species (ROS), and acetylcholinesterase (AChE) levels increased by 2.18-2.24-fold and 1.92-2.24-fold, respectively. Zebrafish ingestion of ZIF-8 was observed, with further analysis showing severe vacuolization and necrosis in tissues, as well as a significant increase in the relative abundance of Proteobacteria in the gut microbiota. Additionally, the study examined the toxicity of co-exposure to ZIF-8 and other pollutants. When ZIF-8 and copper (Cu) were simultaneously introduced, zebrafish survival rates dropped significantly to 79.2%. Co-exposure caused more severe behavioral impairments, with swimming distance reduced by approximately 53.0%, compared to individual exposures to ZIF-8 or Cu. ROS and AChE levels rose by 2.68-3.37-fold and 2.93-3.77-fold, respectively, while tissue vacuolization and necrosis became more pronounced. The relative abundance of Proteobacteria increased to 92.2%. This study provides critical insights into the environmental and ecological impacts of MOFs, emphasizing the necessity of considering these effects for their sustainable application.

Dose-responsive phytotoxicity and oxidative stress induced by metal-organic framework PCN-224 in Arabidopsis thaliana seedlings

Metal-organic frameworks (MOFs) are advanced porous materials composed of metal ions and organic ligands, known for their unique structures and fascinating physio-chemical properties. To ensure their safe production and applications, it is crucial to thoroughly investigate their toxicity and environmental hazards. However, the potential risks of MOFs, particularly their impact on plants remained underexplored. Herein, we systematically assessed the phytotoxicity of PCN-224 on Arabidopsis thaliana (A. thaliana) due to its commercial availability and widespread use. To achieve this goal, A. thaliana seedlings were subjected to PCN-224 concentrations (10-300 µg/mL) and durations (1-12 days) in agar media, with a control group. PCN-224 slightly accelerated seed germination across all concentrations without altering the total germination rate. Exposure to a higher concentration of PCN-224 (300 µg/mL) significantly impaired A. thaliana development, reducing fresh weight (54.0 %) and root length (82.3 %) compared with control; however, lower exposure (10 µg/mL) showed minimal growth inhibition. Fluorescence microscopy showed that PI-labeled PCN-224 particles adhered to root surfaces and internalized in a concentration- and time-dependent manner, with notable xylem accumulation after 2 h. The net photosynthetic rate, transpiration rate, and stomatal conductance decreased by 54.25 %, 62.37 % and 38.53 %, respectively, compared with control, when the material concentration exceeded 100 µg/mL. Regarding the oxidative damage, higher PCN-224 exposure reduced antioxidant levels and downregulation of antioxidant-related genes resulted in a diminished oxidative stress response. Overall, our study highlights the potential risk of MOFs for plant growth and emphasizes the need to assess their environmental impact for sustainable agricultural practices.

Adsorption behavior of ZIF-67 to bisphenol compounds affects combined toxicity on Photobacterium phosphoreum

ZIF-67, as a typical MOF material, is considered a new type of high-potential adsorbent due to its ample surface area and tunable surface chemistry, which has the potential to interact with other contaminants in unforeseen ways, resulting in combined toxicity. To further elucidate this possibility, we chose typical bisphenol compound (BP) which is widely used in commercial manufacturing, to explore the combined toxicity with MOF. MOF showed a high adsorption capacity for BPAF (> 80 %) and the weakest adsorption capacity for BPA (< 10 %), and DFT confirmed the different interaction strengths of MOF for BPs. The difference in adsorption capacity for BPs resulted in different amounts of free BPs, contributing to combined toxicity. Based on flow cytometry and TEM, the results showed that membrane damage was reduced and the ability of ZIF-67 to enter the cell was decreased in the low-concentration ZIF-67 mixing group, and the ability of ZIF-67 to enter the cell was increased in the high-concentration ZIF-67 mixing group, and the membranes were severely damaged. RT-PCR and biochemical indicators measurements helped to explain the underlying toxicity mechanism. This study is of practical significance for the development of environmental guidelines for mixed contaminant effects and accurate risk assessments.

Integrated design and application of stimuli-responsive metal-organic frameworks in biomedicine: current status and future perspectives

In recent years, metal-organic frameworks (MOFs) have garnered widespread attention due to their distinctive attributes, such as high surface area, tunable properties, biodegradability, extremely low density, high loading capacity, diverse chemical functionalities, thermal stability, well-defined pore sizes, and molecular dimensions. Increasingly, biomedical researchers have turned their focus towards their multifaceted development. Among these, stimuli-responsive MOFs, with their unique advantages, have captured greater interest from researchers. This review will delve into the merits and drawbacks of both endogenous and exogenous stimuli-responsive MOFs, along with their application directions. Furthermore, it will outline the characteristics of different synthesis routes of MOFs, exploring various design schemes and modification strategies and their impacts on the properties of MOF products, as well as how to control them. Additionally, we will survey different types of stimuli-responsive MOFs, discussing the significance of various MOF products reported in biomedical applications. We will categorically summarize different strategies such as anticancer therapy, antibacterial treatment, tissue repair, and biomedical imaging, as well as insights into the development of novel MOFs nanomaterials in the future. Finally, this review will conclude by summarizing the challenges in the development of stimuli-responsive MOFs in the field of biomedicine and providing prospects for future research endeavors.

Insight into the mechanisms of combined toxicity of cadmium and flotation agents in luminescent bacteria: Role of micro/nano particles

Currently, risk assessment and pollution management in mines primarily focus on toxic metals, with the flotation agents being overlooked. However, the combined effects of metals and flotation agents in mines remain largely unknown. Therefore, this study aimed to evaluate the combined effects of Cd and two organic flotation agents (ethyl xanthate (EX) and diethyldithiocarbamate (DDTC)), and the associated mechanisms. The results showed that Cd + EX and Cd + DDTC exhibited synergistic toxicity. The EC50 values for luminescent bacteria were 1.6 mg/L and 1.0 mg/L at toxicity unit ratios of 0.3 and 1, respectively. The synergistic effects were closely related with the formation of Cd(EX)2 and Cd(DDTC)2 micro/nano particles, with nano-particles exhibiting higher toxicity. We observed severe cell membrane damage and cell shrinkage of the luminescent bacteria, which were probably caused by secondary harm to cells through the released CS2 during their decomposition inside cells. In addition, these particles induced toxicity by altering cellular levels of biochemical markers and the transcriptional levels of transport proteins and lipoproteins, leading to cell membrane impairment and DNA damage. This study has demonstrated that particulates formed by Cd and flotation agents contribute to the majority of the toxicity of the binary mixture. This study helps to better understand the complex ecological risk of inorganic metals and organic flotation agents in realistic mining environments.

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.

Functional groups effect on the toxicity of modified ZIF-90 to Photobacterium phosphoreum

Zeolitic imidazolate framework (ZIF) is of wide interest in biomedical applications due to its extraordinary properties such as high storage capacity, functionality and favorable biocompatibility. However, more comprehensive safety assessments are still essential before ZIF is broadly used in biomedicine. Using the characteristic that aldehyde groups on the surface of ZIF-90 can be modified with other functional groups, a series of ZIF-90s modified with different functional groups (oxime group, carboxyl group, amino group and sulfhydryl group) were synthesized to investigate the effect of functionalization on the toxicity of ZIF-90. ZIF-90 series showed concentration-dependent toxic effects on Photobacterium phosphoreum T3 and the functionalized ZIF-90s are more toxic than pristine ZIF-90, with the ZIF-90 modified with amino group (ZIF-90-NH2) showing the strongest toxicity (IC50 = 23.06 mg/L). Based on the results of the cellular assay and stability exploration, we concluded that corresponding imidazole-ligand release and the property of positively charged are responsible for the elevated toxicity of ZIF-90-NH2. Cell membrane damage, oxidative damage and luminescence damage are the main contributors to the toxic effects of ZIF-90 series. This study explored the effect of surface functionalization on the toxicity of ZIF and proposed mechanistic clues for the safety application of ZIF.

Recent advances in metal-organic frameworks: Synthesis, application and toxicity

Metal-organic frameworks (MOFs) are a new class of crystalline porous hybrid materials with high porosity, large specific surface area and adjustable channel structure and biocompatibility, which are being investigated with increasing interest for energy storage and conversion, gas adsorption/separation, catalysis, sensing and biomedicine. However, the practical applications of MOFs make them release into the environment inevitable, posing a threat to humans and organisms. In this article, we cover advances in the currently available MOFs synthesis methods and the emerging applications of MOFs, especially in the biomedical field (therapeutic agents and bioimaging). Additionally, after evaluating the current status of main exposure routes and affecting factors in the field of MOFs-toxicity, the molecular mechanism is also clarified and identified. Knowledge gaps are identified from such a summarization and frontier development are explored for MOFs. Afterwards, we also present the limitations, challenges, and future perspectives in the study of the entire life cycle of MOFs. This review emphasizes the need for a more targeted discussion of the latest, widely used and effective versatile material class in order to exploit the full potential of high-performance and non-toxicity MOFs in the future.

Mitigating Metal-Organic Framework (MOF) Toxicity for Biomedical Applications

Metal-organic frameworks (MOFs) are a novel class of crystalline porous materials, consisting of metal ions and organic linkers. These hybrid materials possess exceptional porosity and specific surface area, which have recently garnered significant interest due to their potential applications in gas separation and storage, energy storage, biomedical imaging, and drug delivery. As MOFs are being explored for biomedical applications, it is essential to comprehensively assess their toxicity. Although nearly ninety thousand MOFs have been investigated, evaluating and optimizing their physico-chemical properties in relevant biological systems remain critical for their clinical translation. In this review article, we first provide a brief classification of MOFs based on their chemical structures. We then conduct a comprehensive evaluation of in vitro and in vivo studies that assess the biocompatibility of MOFs. Additionally, we discuss various approaches to mitigate the critical factors associated with MOF toxicity. To this end, the effects of chemistry, particle size, morphology, and particle aggregation are examined. To better understand MOFs' potential toxicity to living organisms, we also delve into the toxicity mechanisms of nanoparticles (NPs). Furthermore, we introduce and evaluate strategies such as surface modification to reduce the inherent toxicity of MOFs. Finally, we discuss current challenges, the path to clinical trials, and new research directions.

Effectively facilitating the degradation of chloramphenicol by the synergism of Shewanella oneidensis MR-1 and the metal-organic framework

Electroactive bacteria (EAB) and metal oxides are capable of synergistically removing chloramphenicol (CAP). However, the effects of redox-active metal-organic frameworks (MOFs) on CAP degradation with EAB are not yet known. This study investigated the synergism of iron-based MOFs (Fe-MIL-101) and Shewanella oneidensis MR-1 on CAP degradation. 0.5 g/L Fe-MIL-101 with more possible active sites led to a three-fold higher CAP removal rate in the synergistic system with MR-1 (initial bacterial concentration of 0.2 at OD₆₀₀), and showed a superior catalytic effect than exogenously added Fe(III)/Fe(II) or magnetite. Mass spectrometry revealed that CAP was transformed into smaller molecular weight and less toxic metabolites in cultures. Transcriptomic analysis showed that Fe-MIL-101 enhanced the expression of genes related to nitro and chlorinated contaminants degradation. Additionally, genes encoding hydrogenases and c-type cytochromes associated with extracellular electron transfer were significantly upregulated, which may contribute to the simultaneous bioreduction of CAP both intracellularly and extracellularly. These results indicated that Fe-MIL-101 can be used as a catalyst to synergize with EAB to effectively facilitate CAP degradation, which might shed new light on the application in the in situ bioremediation of antibiotic-contaminated environments.

Metal-Organic Framework-Based Colloidal Particle Synthesis, Assembly, and Application

Metal-organic frameworks (MOFs) assembled from metal nodes and organic ligands have received significant attention over the past two decades for their fascinating porous properties and broad applications. Colloidal MOFs (CMOFs) not only inherit the intrinsic properties of MOFs, but can also serve as building blocks for self-assembly to make functional materials. Compared to bulk MOFs, the colloidal size of CMOFs facilitates further manipulation of CMOF particles in a single or collective state in a liquid medium. The resulting crystalline order obtained by self-assembly in position and orientation can effectively improve performance. In this review, we summarize the latest developments of CMOFs in synthesis strategies, self-assembly methods, and related applications. Finally, we discuss future challenges and opportunities of CMOFs in synthesis and assembly, by which we hope that CMOFs can be further developed into new areas for a wider range of applications.