MoS2 2D materials induce spinal cord neuroinflammation and neurotoxicity affecting locomotor performance in zebrafish.

MoS2 nanosheets belong to an emerging family of nanomaterials named bidimensional transition metal dichalcogenides (2D TMDCs). The use of such promising materials, featuring outstanding chemical and physical properties, is expected to increase in several fields of science and technology, with an enhanced risk of environmental dispersion and associated wildlife and human exposures. In this framework, the assessment of MoS2 nanosheets toxicity is instrumental to safe industrial developments. Currently, the impact of the nanomaterial on the nervous tissue is unexplored. In this work, we use as in vivo experimental model the early-stage zebrafish, to investigate whether mechano-chemically exfoliated MoS2 nanosheets reach and affect, when added in the behavioral ambient, the nervous system. By high throughput screening of zebrafish larvae locomotor behavioral changes upon exposure to MoS2 nanosheets and whole organism live imaging of spinal neuronal and glial cell calcium activity, we report that sub-acute and prolonged ambient exposures to MoS2 nanosheets elicit locomotor abnormalities, dependent on dose and observation time. While 25 µg mL-1 concentration treatments exerted transient effects, 50 µg mL-1 ones induced long-lasting changes, correlated to neuroinflammation-driven alterations in the spinal cord, such as astrogliosis, glial intracellular calcium dysregulation, neuronal hyperactivity and motor axons retraction. By combining integrated technological approaches to zebrafish, we described that MoS2 2D nanomaterials can reach, upon water (i.e. ambient) exposure, the nervous system of larvae, resulting in a direct neurological damage.

The use of LA-ICP-MS as an auxiliary tool to assess the pulmonary toxicity of molybdenum(IV) sulfide (MoS2) nano- and microparticles.

OBJECTIVES: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has considerable applicative potential for both qualitative and quantitative analyses of elemental spatial distribution and concentration. It provides high resolutions at pg-level detection limits. These qualities make it very useful for analyzing biological samples. The present study responds to the growing demand for adequate analytical methods which would allow to assess the distribution of nanostructured molybdenum(IV) disulfide (MoS2) in organs. It was also motivated by an apparent lack of literature on the biological effects of MoS2 in living organisms. The study was aimed at using LA-ICP-MS for comparing micro- and nanosized MoS2 ditribution in selected rat tissue samples (lung, liver, brain and spleen tissues) after the intratracheal instillation (7 administrations) of MoS2 nano- and microparticles vs. controls. MATERIAL AND METHODS: The experimental study, approved by the Ethics Committee for Animal Experiments was performed using albino Wistar rats. This was performed at 2-week intervals at a dose of 5 mg/kg b.w., followed by an analysis after 90 days of exposure. The MoS2 levels in control tissues were determined with the laser ablation system at optimized operating conditions. The parameter optimization process for the LA system was conducted using The National Institute of Standards and Technology (NIST) glass standard reference materials. RESULTS: Instrument parameters were optimized. The study found that molybdenum (Mo) levels in the lungs of microparticle-exposed rats were higher compared to nanoparticle-exposed rats. The opposite results were found for liver and spleen tissues. Brain Mo concentrations were below the detection limit. CONCLUSIONS: The LA-ICP-MS technique may be used as an important tool for visualizing the distribution of Mo on the surface of soft samples through quantitative and qualitative elemental mapping. Int J Occup Med Environ Health. 2024;37(1):18-33.

Controlled decoration of nanoceria on the surface of MoS2nanoflowers to improve the biodegradability and biocompatibility inDrosophila melanogastermodel.

In recent years, nanozymes based on two-dimensional (2D) nanomaterials have been receiving great interest for cancer photothermal therapy. 2D materials decorated with nanoparticles (NPs) on their surface are advantageous over conventional NPs and 2D material based systems because of their ability to synergistically improve the unique properties of both NPs and 2D materials. In this work, we report a nanozyme based on flower-like MoS2nanoflakes (NFs) by decorating their flower petals with NCeO2using polyethylenimine (PEI) as a linker molecule. A detailed investigation on toxicity, biocompatibility and degradation behavior of fabricated nanozymes in wild-typeDrosophila melanogastermodel revealed that there were no significant effects on the larval size, morphology, larval length, breadth and no time delay in changing larvae to the third instar stage at 7-10 d for MoS2NFs before and after NCeO2decoration. The muscle contraction and locomotion behavior of third instar larvae exhibited high distance coverage for NCeO2decorated MoS2NFs when compared to bare MoS2NFs and control groups. Notably, the MoS2and NCeO2-PEI-MoS2NFs treated groups at 100µg ml-1covered a distance of 38.2 mm (19.4% increase when compared with control) and 49.88 mm (no change when compared with control), respectively. High-resolution transmission electron microscopy investigations on the new born fly gut showed that the NCeO2decoration improved the degradation rate of MoS2NFs. Hence, nanozymes reported here have huge potential in various fields ranging from biosensing, cancer therapy and theranostics to tissue engineering and the treatment of Alzheimer's disease and retinal therapy.

Probing Variations of Reduction Activity at the Plasma Membrane Using a Targeted Ratiometric FRET Probe.

Plasma membrane (PM) is the turntable of various reactions that regulate essential functionalities of cells. Among these reactions, the thiol disulfide exchange (TDE) reaction plays an important role in cellular processes. We herein designed a selective probe, called membrane reduction probe (MRP), that is able to report TDE activity at the PM. MRP is based on a green emitting BODIPY PM probe connected to rhodamine through a disulfide bond. MRP is fluorogenic as it is turned off in aqueous media due to aggregation-caused quenching, and once inserted in the PM, it displays a bright red signal due to an efficient fluorescence energy resonance transfer (FRET) between the BODIPY donor and the rhodamine acceptor. In the PM model, the MRP can undergo TDE reaction with external reductive agents as well as with thiolated lipids embedded in the bilayer. Upon TDE reaction, the FRET is turned off and a bright green signal appears allowing a ratiometric readout of this reaction. In cells, the MRP quickly labeled the PM and was able to probe variations of TDE activity using ratiometric imaging. With this tool in hand, we were able to monitor variations of TDE activity at the PM under stress conditions, and we showed that cancer cell lines presented a reduced TDE activity at the PM compared to noncancer cells.

Sulfur vacancies affect the environmental fate, corona formation, and microalgae toxicity of molybdenum disulfide nanoflakes.

Sulfur vacancy (SV) defects have been engineered in two-dimensional (2D) transition metal dichalcogenides (TMDs) for high performance applications in various fields involving environmental protection. Understanding the influence of SVs on the environmental fate and toxicity of TMDs is critical for evaluating their risk. Our work discovered that SVs (with S/Mo ratios of 1.65 and 1.32) reduced the dispersibility and promoted aggregation of 2H phase molybdenum disulfide (2H-MoS2, a hot TMD) in aqueous solution. The generation capability of •O2- and •OH was increased and the dissolution of 2H-MoS2 was significantly accelerated after SVs formation. Different with pristine form, S-vacant 2H-MoS2 preferentially harvested proteins (i.e., forming protein corona) involved in antioxidation, photosynthetic electron transport, and the cytoskeleton structure of microalgae. These proteins contain a higher relative number of thiol groups, which exhibited stronger affinity to S-vacant than pristine 2H-MoS2, as elucidated by density functional theory calculations. Notably, SVs aggravated algal growth inhibition, oxidative damage, photosynthetic efficiency and cell membrane permeability reduction induced by 2H-MoS2 due to increased free radical yield and the specific binding of functional proteins. Our findings provide insights into the roles of SVs on the risk of MoS2 while highlighting the importance of rational design for TMDs application.

Aptamer-PROTAC Conjugates (APCs) for Tumor-Specific Targeting in Breast Cancer.

Development of proteolysis targeting chimeras (PROTACs) is emerging as a promising strategy for targeted protein degradation. However, the drug development using the heterobifunctional PROTAC molecules is generally limited by poor membrane permeability, low in vivo efficacy and indiscriminate distribution. Herein an aptamer-PROTAC conjugation approach was developed as a novel strategy to improve the tumor-specific targeting ability and in vivo antitumor potency of conventional PROTACs. As proof of concept, the first aptamer-PROTAC conjugate (APC) was designed by conjugating a BET-targeting PROTAC to the nucleic acid aptamer AS1411 (AS) via a cleavable linker. Compared with the unmodified BET PROTAC, the designed molecule (APR) showed improved tumor targeting ability in a MCF-7 xenograft model, leading to enhanced in vivo BET degradation and antitumor potency and decreased toxicity. Thus, the APC strategy may pave the way for the design of tumor-specific targeting PROTACs and have broad applications in the development of PROTAC-based drugs.

Synergistic Photodynamic and Photothermal Antibacterial Activity of In Situ Grown Bacterial Cellulose/MoS2-Chitosan Nanocomposite Materials with Visible Light Illumination.

Owing to the rise in prevalence of multidrug-resistant pathogens attributed to the overuse of antibiotics, infectious diseases caused by the transmission of microbes from contaminated surfaces to new hosts are an ever-increasing threat to public health. Thus, novel materials that can stem this crisis, while also functioning via multiple antimicrobial mechanisms so that pathogens are unable to develop resistance to them, are in urgent need. Toward this goal, in this work, we developed in situ grown bacterial cellulose/MoS2-chitosan nanocomposite materials (termed BC/MoS2-CS) that utilize synergistic membrane disruption and photodynamic and photothermal antibacterial activities to achieve more efficient bactericidal activity. The BC/MoS2-CS nanocomposite exhibited excellent antibacterial efficacy, achieving 99.998% (4.7 log units) and 99.988% (3.9 log units) photoinactivation of Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, respectively, under visible-light illumination (xenon lamp, 500 W, λ ≥ 420 nm, and 30 min). Mechanistic studies revealed that the use of cationic chitosan likely facilitated bacterial membrane disruption and/or permeability, with hyperthermia (photothermal) and reactive oxygen species (photodynamic) leading to synergistic pathogen inactivation upon visible-light illumination. No mammalian cell cytotoxicity was observed for the BC/MoS2-CS membrane, suggesting that such composite nanomaterials are attractive as functional materials for infection control applications.

Facile synthesis of porous MoS2nanofibers for efficient drug delivery and cancer treatment.

Porous MoS2nanofibers were synthesized by electroplating and post-annealing and applied in a responsive drug delivery system. The one-dimensional (1D) MoS2nanofibers displayed a high specific surface area, controllable morphology, and uniform size, serving as a promising drug carrier for chemotherapy. After surface modification with polyethylene glycol (PEG) through PEGylation, the MoS2/PEG composite displayed excellent physical/chemical stability and biocompatibility. More importantly, MoS2/PEG loaded with doxorubicin (DOX) exhibited a controllable release responsive to pH and near-infrared (NIR) irradiation and demonstrated precise DOX dose release. Such remarkable anticancer effects were mainly attributed to outstanding photothermal performance and stability of porous MoS2nanofibers. This work offered a new opportunity of employing porous MoS2nanofibers as drug carriers for effective cancer chemotherapy.

Enhanced antimicrobial activity of konjac glucomannan nanocomposite films for food packaging.

This paper aims at providing a new strategy for developing konjac glucomannan-based antibacterial films with excellent performances. Here, novel nanocomposite films based on photodynamic and photothermal synergism strategy were developed by incorporating graphite carbon nitride nanosheets/MoS2 nanodots (CNMo) into konjac glucomannan (KGM) matrix. Scanning electron microscope, transmission electron microscope, high resolution transmission, high angle annular dark field and element mapping confirmed the successful fabrication of CNMo. The steady and dynamic rheological behavior as well as the good stability of film-forming solution showed that the intermolecular hydrogen bonding was formed. The influences of CNMo content on the structural, mechanical and thermal properties as well as hydrophobicity of KGM films were investigated. This film has a broad-spectrum antibacterial activity. It could prolong the shelf life of cherry tomatoes. Moreover, hemolysis and cells experiment confirm that this film is safe. This strategy is expected to broaden the application of antibacterial packaging.

Augmented cytotoxicity using the physical adsorption of Poloxamer 188 on allicin-loaded gelatin nanoparticles.

OBJECTIVES: The aim of this work was to study the effect of the physically adsorbed Poloxamer 188 coating polymer on the cytotoxic activity of allicin-loaded gelatin nanoparticles. METHODS: The double desolvation method was utilised to prepare the nanoparticles which were characterised for particle size (PS), polydispersity index (PDI) and zeta potential and visualised using transmission electron microscopy. The coating density of the used polymer was determined using 1H-nuclear magnetic resonance (1H-NMR); 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to evaluate the cytotoxicity on HepG-2 cell lines. KEY FINDINGS: The particles were spherical possessing a PS of 714 ± 25.21 nm and a PDI of 0.663 ± 0.143. These results together with the 1H-NMR results analysis confirmed the efficient coating of Poloxamer 188. The coating of particles rendered them more cytotoxic, scoring an IC50 of 6.736 µm (2-folds lower than the uncoated counter parts and 4-folds lesser than the allicin solution), and apt for cancer-targeting. Moreover, the prepared nanoparticles were stable to gamma-sterilisation and to a storage of 12 months. CONCLUSIONS: Augmented cytotoxicity on HepG-2 cell lines was obtained using the physical adsorption of an abundant and relatively cheap material, Poloxamer 188, on allicin-loaded gelatin nanoparticles.

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

The utilization of tungsten disulfide (WS2) nanomaterials in distinct applications is raising due to their unique physico-chemical properties, such as low friction coefficient and high strength, which highlights the necessity to study their potential toxicological effects, due to the potential increase of environmental and human exposure. The aim of this work was to analyze commercially available aqueous dispersions of monolayer tungsten disulfide (2D WS2) nanomaterials with distinct lateral size employing a portfolio of physico-chemical and toxicological evaluations. The structure and stoichiometry of monolayer tungsten disulfide (WS2-ACS-M) and nano size monolayer tungsten disulfide (WS2-ACS-N) was analyzed by Raman spectroscopy, whereas a more quantitative approach to study the nature of formed oxidized species was undertaken employing X-ray photoelectron spectroscopy. Adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the ecotoxicology model Saccharomyces cerevisiae were selected as unicellular eukaryotic systems to assess the cytotoxicity of the nanomaterials. Cell viability and reactive oxygen species (ROS) determinations demonstrated different toxicity levels depending on the cellular model used. While both 2D WS2 suspensions showed very low toxicity towards the A549 cells, a comparable concentration (160 mg L-1) reduced the viability of yeast cells. The toxicity of a nano size 2D WS2 commercialized in dry form from the same provider was also assessed, showing ability to reduce yeast cells viability as well. Overall, the presented data reveal the physico-chemical properties and the potential toxicity of commercial 2D WS2 aqueous suspensions when interacting with distinct eukaryotic organisms, showing differences in function of the biological system exposed.

Persistence and ingestion characteristics of phytochemical volatiles as bio-fumigants in Sitophilus oryzae adults.

Fumigant toxicity of phytochemical volatiles has been widely reported against stored product insect pests. Such volatiles are considered as natural fumigants and bio-fumigants in post-harvest food protection research. In the present study, persistence and ingestion of diallyl disulfide, citral, eucalyptol, eugenol and menthol were investigated in Sitophilus oryzae adults in comparison with fumigant toxicity and microstructural impact in elytra. The fumigant toxicity bioassay was performed with increasing concentrations of phytochemical volatiles at 25, 125, 250 and 500 µL/L air against S. oryzae adults in 50 mL glass vials. The phytochemical residues were examined from the treated adults by Gas Chromatography coupled with Flame Ionization Detector (GC-FID) and their pathological impacts on the elytral surface was observed under Scanning Electron Microscopy (SEM). After 72 h of fumigation, diallyl disulfide and eucalyptol were identified as potential fumigants with 5.24 and 8.30 µL/L air LC50 values, respectively. GC-FID analyses showed that diallyl disulfide and eucalyptol molecules persistence (1.29 and 2.60 ppb persistence with 0.94 and 0.90 r2 values respectively at 72 h exposure) on the body surface of weevil was positively correlated with the fumigation exposure and toxicity. Whereas, phytochemical molecules ingestion into the body of weevils was not directly linked with the insect mortalities. The SEM observations indicated that diallyl disulfide and eucalyptol molecules caused severe microstructural impacts on the elytra of weevils compared to other molecules. As a result, the present study suggested that phytochemical fumigants are persisted on the body surface and caused insecticidal toxicities in S. oryzae adults. In addition, it was predicted that persisted molecules might be entered into the body of weevils via cuticular penetration.

Multi-Encapsulation Combination of O/W/O Emulsions with Polyurea Microcapsules for Controlled Release and Safe Application of Dimethyl Disulfide.

Dimethyl disulfide (DMDS), a promising alternative fumigant, has been highly desirable for excellent management of soil pests and diseases. However, high volatility and moderate toxicity of this sulfide limit its application. To address these issues, a novel controlled release formulation of DMDS was proposed employing multiple emulsions and polyurea microcapsules (DMDS@MEs-MCs). The successful combination of the two technologies was revealed by confocal laser scanning microscopy, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared. According to the multiple encapsulation structure, the encapsulation efficiency decreased by only 3.13% after thermal storage, compared with a 15.21% decrease of microcapsules made with only a monolayer film. DMDS@MEs-MCs could effectively control the release of active ingredient, which increased applicator and environmental safety during application. Moreover, it could be facilely used by spraying and drip irrigation instead of a special fumigation device. The innovative formulation exhibited better control efficacy on soil pathogens (Fusarium spp. and Phytophthora spp.) and root-knot nematodes (Meloidogyne spp.) than DMDS technical concentration (DMDS TC). In addition, it did not inhibit seed germination after 10 days when the plastic film was removed from the fumigated soil. This method appears to be of broad interest for the development of safe and handy fumigant application.

Physiological and molecular responses in halotolerant Dunaliella salina exposed to molybdenum disulfide nanoparticles.

Molybdenum disulfide nanoparticles (MoS2 NPs) has emerged as the promising nanomaterial with a wide array of applications in the biomedical, industrial and environmental field. However, the potential effect of MoS2 NPs on marine organisms has yet to be reported. In this study, the effect of MoS2 NPs on the physiological index, subcellular morphology, transcriptomic profiles of the marine microalgae Dunaliella salina was investigated for the first time. exhibited "doping-like" effects on marine microalgae; Growth stimulation was 193.55%, and chlorophyll content increased 1.61-fold upon the addition of 50 µg/L MoS2 NPs. Additionally, exposure to MoS2 NPs significantly increased the protein and carbohydrate content by 2.03- and 1.56-fold, respectively. The antioxidant system was activated as well to eliminate the adverse influence of reactive oxygen species (ROS). Transcriptomic analysis revealed that genes involved in porphyrin synthesis, glycolysis/gluconeogenesis, tricarboxylic acid cycle and DNA replication were upregulated upon MoS2 NPs exposure, which supports the mechanistic role of MoS2 NPs in improving cellular growth and photosynthesis. The "doping-like" effects on marine algae suggest that the low concentration of MoS2 NPs might change the rudimentary ecological composition in the ocean.

Surface atomic arrangement of nanomaterials affects nanotoxicity.

Understanding the roles of the properties of nanomaterials in biological interactions is a key issue in their safe applications, but the surface atomic arrangement, as an important property of engineered nanomaterials (ENMs), remains largely unknown. Herein, the interfacial interactions (affinity sites and intensity) between monolayer MoS2 and zebrafish embryos mediated by 1 T phase surface atomic arrangement (octahedral coordination) and the 2H phase surface atomic arrangement (triangular prism coordination) MoS2 nanosheets were studied. 1 T-MoS2 first bound to phosphate and then proteins on the chorion, while the adhesion of 2H-MoS2 occurred in the opposite order. The binding affinity of 2H-MoS2 with embryos was higher than that of 1 T-MoS2, and the former material changed the protein structure from ß-sheets to turns and bends and random coils. Compared to 1 T-MoS2, 2H-MoS2 more readily entered embryos, which was facilitated by caveolae-mediated endocytosis, and caused higher developmental toxicity. Furthermore, metabolic pathways related to amino acid and protein biosynthesis and energy metabolism were affected by the nanomaterial surface atomic arrangements. The above results provide insights into the designs, applications and risk assessments of nanomaterials by the surface atomic arrangement regulation.

Influence of Size and Phase on the Biodegradation, Excretion, and Phytotoxicity Persistence of Single-Layer Molybdenum Disulfide.

The increasing applications of single-layer molybdenum disulfide (SLMoS2) pose great potential risks associated with environmental exposure. This study found that metallic-phase SLMoS2 with nanoscale (N-1T-SLMoS2, ∼400 nm) and microscale (M-1T-SLMoS2, ∼3.6 µm) diameters at 10-25 mg/L induced significant algal growth inhibition (maximum 72.7 and 74.6%, respectively), plasmolysis, and oxidative damage, but these alterations were recoverable. Nevertheless, membrane permeability, chloroplast damage, and chlorophyll biosynthesis reduction were persistent. By contrast, the growth inhibition (maximum 55.3%) and adverse effects of nano-sized semiconductive-phase SLMoS2 (N-2H-SLMoS2, ∼400 nm) were weak and easily alleviated after 96 h of recovery. N-1T-SLMoS2 (0.011 µg/h) and N-2H-SLMoS2 (0.008 µg/h) were quickly biodegraded to soluble Mo compared with M-1T-SLMoS2 (0.004 µg/h) and excreted by algae. Incomplete biodegradation of SLMoS2 (26.8-43.9%) did not significantly mitigate its toxicity. Proteomics and metabolomics indicated that the downregulation of proteins (50.7-99.2%) related to antioxidants and photosynthesis and inhibition of carbon fixation and carbohydrate metabolism contributed to the persistent phytotoxicity. These findings highlight the roles and mechanisms of the size and phase in the persistent phytotoxicity of SLMoS2, which has potential implications for risk assessment and environmental applications of nanomaterials.

Employment of cytology for in vitro skin irritation test using a reconstructed human epidermis model, Keraskin™.

Skin irritation tests using reconstructed human epidermis (RhE) employ viability as an endpoint, but color interference or borderline results are often problematic. We examined whether the cytology of cells from treated RhE could determine skin irritancy. Six chemicals (three irritants; DnP, 1-B, PH, three non-irritants; DP, APA, HS) were evaluated in a RhE, Keraskin™. DP, HS, and PH were clearly classified with viability, but DnP, 1-B, and APA were often falsely determined, due to borderline values falling near the cutoff, 50%. In histology, the tissues treated with DnP, 1-B, and PH showed erosion of the stratum corneum, vacuolization, and necrosis in the basal layer. DP- and HS-treated tissues showed relatively normal morphology but APA induced necrosis similar to irritants. Cytology revealed that DnP, 1-B or PH depleted cells and induced irregular and abnormal cell shapes. In contrast, relatively regular and normal shapes and clear distinction between the nucleus and cytoplasm was observed for DP, APA and HS. To further confirm it, additional 10 substances, including false positives from OECD TG 439, were tested. Overall (16 substances in total), cytology: total area predicted the skin irritancy of test chemicals with the highest accuracy (87.5%) followed by cytology: cell count (81.3%), histology (75%) and viability (68.8%), confirming the utility of cytology as an alternative endpoint in the skin irritation test using RhE.