Toxicological assessment of commercial monolayer tungsten disulfide nanomaterials aqueous suspensions using human A549 cells and the model fungus Saccharomyces cerevisiae

Trends and prospects of 2-D tungsten disulphide (WS2) hybrid nanosystems for environmental and biomedical applications

Recently, 2D layered transition metal dichalcogenides (TMDCs) with their ultrathin sheet nanostructure and diversified electronic structure have drawn attention for various advanced applications to achieve high-performance parameters. Unique 2D TMDCs mainly comprise transition metal and chalcogen element where chalcogen element layers sandwich the transition metal element layer. In such a case, various properties can be enhanced and controlled depending on the targeted application. Among manipulative 2D TMDCs, tungsten disulphide (WS2) is one of the emerging nano-system due to its fascinating properties in terms of direct band gap, higher mobility, strong photoluminescence, good thermal stability, and strong magnetic field interaction. The advancement in characterization techniques, especially scattering techniques, can help in study of opto-electronic properties of 2D TMDCs along with determination of layer variations and investigation of defect. In this review, the fabrication and applications are well summarized to optimize an appropriate WS2-TMDCs assembly according to focused field of research. Here, the scientific investigations on 2D WS2 are studied in terms of its structure, role of scattering techniques to study its properties, and synthesis routes followed by its potential applications for environmental remediation (e.g., photocatalytic degradation of pollutants, gas sensing, and wastewater treatment) and biomedical domain (e.g., drug delivery, photothermal therapy, biomedical imaging, and biosensing). Further, a special emphasis is given to the significance of 2D WS2 as a substrate for surface-enhanced Raman scattering (SERS). The discussion is further extended to commercial and industrial aspects, keeping in view major research gaps in existing research studies.

Effects of WS2 Nanosheets on N2-fixing Cyanobacteria: ROS overproduction, cell membrane damage, and cell metabolic reprogramming

The ecotoxicity of tungsten disulfide (WS₂) nanomaterials remains unclear so far. Here, the toxicity of WS₂ nanosheets on N₂-fixing cyanobacteria (Nostoc sphaeroides) was evaluated. Specifically, Nostoc were cultivated in media spiked with different concentrations of WS₂ nanosheets (0, 0.05, 0.1 and 0.5 mg/L) for 96 h. Relative to unexposed cells, WS₂ nanosheets at 0.5 mg/L significantly decreased cell density, content of total sugar and protein by 10.9 %, 0.43 %, and 6.1 %, respectively. Gas chromatography-mass spectrometry (GC-MS)-based metabolomics revealed that WS₂ nanosheets exposure altered the metabolite profile of Nostoc in a dose-dependent manner. Energy metabolism related pathways, including the Calvin-Benson-Bassham (CBB) cycle and tricarboxylic acid (TCA) cycle, were significantly inhibited. In addition, WS₂ nanosheets exposure resulted in downregulation (20-40 %) of S-containing amino acids (cystine, methionine, and cysteine) and sulfuric acid. Additionally, fatty acids and antioxidant-related compounds (formononetin, catechin, epigallocatechin, dehydroascorbic acid, and alpha-tocopherol) in Nostoc were drastically decreased by 4-50 % upon exposure to WS₂ nanosheets, which implies oxidative stress induced by the nanomaterials. Biochemical assays for reactive oxygen species (ROS) and malondialdehyde (MDA) confirmed that WS₂ nanosheets triggered ROS overproduction and induced lipid peroxidation. Taken together, WS₂ exposure perturbed carbon (C), nitrogen (N), and sulfate (S) metabolism of Nostoc, which may influence C, N, and S cycling, given the important roles of cyanobacteria in these processes. These results highlight the need for caution in the application and environmental release of WS₂ nanomaterials to prevent unintended environmental impacts due to their potential ecotoxicity.

Differential pulse voltammetry determination of salbutamol using disulfite tungsten/activated carbon modified glassy carbon electrode

In the present article, the disulfide tungsten/activated carbon derived from Eichhornia crassipes (WS₂/AC) was synthesized by the hydrothermal process. The received materials were examined by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray - mapping, and nitrogen adsorption/desorption isotherms. The morphology of WS₂/AC was tailored to have a micro/meso/macro structure that facilized large electric conductivity and quick ion diffusion. The WS₂/AC sample was used as an electrode modifier for developing an electrochemical sensor for salbutamol detection. WS₂/AC exhibited excellent oxidation toward salbutamol. Through some optimized conditions, the electrochemical signal of the proposed sensor varied linearly to the salbutamol concentration ranging from 1 to 210 μM with a low LOD (detection limit) of 0.52 μM. The developed sensor showed several merits: easy producing, convenient usage, fabulous selectivity, and good repeatability as well as reproducibility. Finally, the suggested technique can be applied to determine salbutamol in people's biological fluid with satisfactory recoveries of 98.5-104.4% and without statistics different from standard HPLC.

Toxicological effects of WS2 nanomaterials on rice plants and associated soil microbes

As an important member of transition-metal dichalcogenides family, tungsten disulfides nanomaterials (WS₂ NMs) have a wide range of applications. To date, their environmental risks remain largely unknown. In this study, rice plants were grown in soil amended with different concentrations (0, 10, and 100 mg/kg) of WS₂ NMs for 4 weeks. WS₂ NMs at 100 mg/kg significantly increased MDA (malondialdehyde) content and decreased total antioxidant capacities of leaves, indicating the oxidative response induced by WS₂ NMs. Meanwhile, WS₂ NMs at 100 mg/kg significantly decreased root biomass compared to control, indicating the negative impacts of WS₂ NMs on plant growth. While exposure to 100 mg/kg WS₂ NMs significantly increased soil bioavailable Cu, Fe, Zn, and Olsen-P, and increased the content of Cu, Fe, Zn, and P in rice leaves. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis showed that W was taken up by rice roots and translocated into leaves. The impact of WS₂ on soil microbial communities was evaluated by 16S rRNA gene sequencing. WS₂ NMs at 100 mg/kg significantly decreased soil microbial diversity, as indicated by decreased Shannon index. In addition, 100 mg/kg WS₂ shifted the soil microbial profile, the relative abundance of the phylum Acidobacteriota decreased, and Actinobacteriota increased. Taken together, the soil microbial community's diversity and composition have been altered upon exposure to 100 mg/kg WS₂ NMs. The results of this study provide some basic information regarding the environmental behavior and phytotoxicity of WS₂ NMs, which is valuable for safe use of WS₂ NMs.

Toxicological assessment of nanocrystalline metal alloys with potential applications in the aeronautical field

The development of new candidate alloys with outstanding characteristics for their use in the aeronautical field is one of the main priorities for the sector. In this context, nanocrystaline (nc) alloys are considered relevant materials due to their special features, such as their exceptional physical and mechanical properties. However, another important point that needs to be considered with newly developed alloys is the potential toxicological impact that these materials may have in humans and other living organisms. The aim of this work was to perform a preliminary toxicological evaluation of three nc metal alloys (WCu, WAl and TiAl) in powder form produced by mechanical alloying, applying different in vitro assays, including a mix of W-Cu powders with standard grain size in the experiments to stablish comparisons. The effects of the direct exposure to powder suspensions and/or to their derived leachates were analysed in three model organisms representative of human and environmental exposures (the adenocarcinomic human alveolar basal epithelial cell line A549, the yeast Saccharomyces cerevisiae and the Gram negative bacterium Vibrio fischeri). Altogether, the results obtained provide new insights about the potential harmful effects of the selected nc alloys, showing that, from a toxicological perspective, nc TiAl is the safest candidate in the model organisms and conditions tested.

Low Toxicological Impact of Commercial Pristine Multi-Walled Carbon Nanotubes on the Yeast Saccharomyces cerevisiae

Carbon nanotubes (CNTs) have attracted the attention of academy and industry due to their potential applications, being currently produced and commercialized at a mass scale, but their possible impact on different biological systems remains unclear. In the present work, an assessment to understand the toxicity of commercial pristine multi-walled carbon nanotubes (MWCNTs) on the unicellular fungal model Saccharomyces cerevisiae is presented. Firstly, the nanomaterial was physico-chemically characterized, to obtain insights concerning its morphological features and elemental composition. Afterwards, a toxicology assessment was carried out, where it could be observed that cell proliferation was negatively affected only in the presence of 800 mg L^-1 for 24 h, while oxidative stress was induced at a lower concentration (160 mg L^-1) after a short exposure period (2 h). Finally, to identify possible toxicity pathways induced by the selected MWCNTs, the transcriptome of S. cerevisiae exposed to 160 and 800 mg L^-1, for two hours, was studied. In contrast to a previous study, reporting massive transcriptional changes when yeast cells were exposed to graphene nanoplatelets in the same exposure conditions, only a small number of genes (130) showed significant transcriptional changes in the presence of MWCNTs, in the higher concentration tested (800 mg L^-1), and most of them were found to be downregulated, indicating a limited biological response of the yeast cells exposed to the selected pristine commercial CNTs.