Impact of lithiated cobalt oxide and phosphate nanoparticles on rainbow trout gill epithelial cells

Ecotoxicological assessment, oxidative response, and enzyme activity disorder of the rotifer Brachionus asplanchnoidis exposed to a toxic cocktail of spent lithium-ion battery leachate

Spent lithium-ion batteries (LIBs) have emerged as a major source of waste due to their low recovery rate. The physical disposal of spent LIBs can lead to the leaching of their contents into the surrounding environment. While it is widely agreed that hazardous substances such as nickel and cobalt in the leachate can pose a threat to the environment and human health, the overall composition and toxicity of LIB leachate remain unclear. In this study, a chemical analysis of leachate from spent LIBs was conducted to identify its primary constituents. The ecotoxicological parameters of the model organism, rotifer Brachionus asplanchnoidis, were assessed to elucidate the toxicity of the LIB leachate. Subsequent experiments elucidated the impacts of the LIB leachate and its representative components on the malondialdehyde (MDA) level, antioxidant capacity, and enzyme activity of B. asplanchnoidis. The results indicate that both the LIB leachate and its components are harmful to individual rotifers due to the adverse effects of stress-induced disturbances in biochemical indicators, posing a threat to population development. The intensified poisoning phenomenon under combined stress suggests the presence of complex synergistic effects among the components of LIB leachate. Due to the likely environmental and biological hazards, LIBs should be strictly managed after disposal. Additionally, more economical and eco-friendly recycling and treatment technologies need to be developed and commercialized.

Optimized Bags of Artificial Neural Networks Can Predict the Viability of Organisms Exposed to Nanoparticles

Prediction of organismal viability upon exposure to a nanoparticle in varying environments─as fully specified at the molecular scale─has emerged as a useful figure of merit in the design of engineered nanoparticles. We build on our earlier finding that a bag of artificial neural networks (ANNs) can provide such a prediction when such machines are trained with a relatively small data set (with ca. 200 examples). Therein, viabilities were predicted by consensus using the weighted means of the predictions from the bags. Here, we confirm the accuracy and precision of the prediction of nanoparticle viabilities using an optimized bag of ANNs over sets of data examples that had not previously been used in the training and validation process. We also introduce the viability strip, rather than a single value, as the prediction and construct it from the viability probability distribution of an ensemble of ANNs compatible with the data set. Specifically, the ensemble consists of the ANNs arising from subsets of the data set corresponding to different splittings between training and validation, and the different bags (k-folds). A k - 1 k machine uses a single partition (or bag) of k - 1 ANNs each trained on 1/k of the data to obtain a consensus prediction, and a k-bag machine quorum samples the k possible k - 1 k machines available for a given partition. We find that with increasing k in the k-bag or k - 1 k machines, the viability strips become more normally distributed and their predictions become more precise. Benchmark comparisons between ensembles of 4-bag machines and 3 4 fraction machines suggest that the 3 4 fraction machine has similar accuracy while overcoming some of the challenges arising from divergent ANNs in the 4-bag machines.

Influences of l-ascorbic acid on cytotoxic, biochemical, and genotoxic damages caused by copper II oxide nanoparticles in the rainbow trout gonad cells-2

In parallel with the raising use of copper oxide nanoparticles (CuO NPs) in various industrial and commercial practices, scientific reports on their release to the environment and toxicity are increasing. The toxicity of CuO NPs is mostly based on their oxidative stress. Therefore, it is necessary to investigate the efficacy of well-known therapeutic agents as antioxidants against CuO NPs damage. This study aimed to investigate the mechanism of this damage and to display whether l-ascorbic acid could preserve against the cell toxicities induced by CuO NPs in the rainbow trout gonad cells-2 (RTG-2). While CuO NPs treatment significantly diminished cell viability, the l-ascorbic acid supplement reversed this. l-ascorbic acid treatment reversed the changes in expressions of sod1, sod2, gpx1a, and gpx4b genes while playing a supportive role in the changes in the expression of the cat gene induced by CuO NPs treatment. Moreover, CuO NPs treatment caused an upregulation in the expressions of growth-related genes (gh1, igf1, and igf2) and l-ascorbic acid treatment further increased these effects. CuO NPs treatment significantly up-regulated the expression of the gapdh gene (glycolytic enzyme gene) compared to the control group, and l-ascorbic acid treatment significantly down-regulated the expression of the gapdh gene compared to CuO NPs treatment. The genotoxicity test demonstrated that l-ascorbic acid treatment increased the genotoxic effect caused by CuO NPs by acting as a co-mutagen. Based on the findings, l-ascorbic acid has the potential to be sometimes inhibitory and sometimes supportive of cellular mechanisms caused by CuO NPs.

Expression Patterns of Energy-Related Genes in Single Cells Uncover Key Isoforms and Enzymes That Gain Priority Under Nanoparticle-Induced Stress

Cellular responses to nanoparticles (NPs) have been largely studied in cell populations, providing averaged values that often misrepresent the true molecular processes that occur in the individual cell. To understand how a cell redistributes limited molecular resources to achieve optimal response and survival requires single-cell analysis. Here we applied multiplex single molecule-based fluorescence in situ hybridization (fliFISH) to quantify the expression of 10 genes simultaneously in individual intact cells, including glycolysis and glucose transporter genes, which are critical for restoring and maintaining energy balance. We focused on individual gill epithelial cell responses to lithium cobalt oxide (LCO) NPs, which are actively pursued as cathode materials in lithium-ion batteries, raising concerns about their impact on the environment and human health. We found large variabilities in the expression levels of all genes between neighboring cells under the same exposure conditions, from only a few transcripts to over 100 copies in individual cells. Gene expression ratios among the 10 genes in each cell uncovered shifts in favor of genes that play key roles in restoring and maintaining energy balance. Among these genes are isoforms that can secure and increase glycolysis rates more efficiently, as well as genes with multiple cellular functions, in addition to glycolysis, including DNA repair, regulation of gene expression, cell cycle progression, and proliferation. Our study uncovered prioritization of gene expression in individual cells for restoring energy balance under LCO NP exposures. Broadly, our study gained insight into single-cell strategies for redistributing limited resources to achieve optimal response and survival under stress.

Isolation Methods Influence the Protein Corona Composition on Gold-Coated Iron Oxide Nanoparticles

Upon exposure to a biological environment, nanoparticles (NPs) acquire biomolecular coatings, the most studied of which is the protein corona. This protein corona gives NPs a new biological identity that will determine various biological responses including cellular uptake, biodistribution, and toxicity. The standard method to isolate NPs from a biological matrix in order to study their coronas is centrifugation, but more gentle means of retrieval may enable deeper understanding of both irreversibly bound hard coronas and more loosely bound soft coronas. In this study, magnetic gold-coated iron oxide NPs were incubated with rainbow trout gill cell total protein extracts and mass spectrometric proteomic analysis was conducted to determine the composition of the protein coronas isolated by either centrifugation or magnetic retrieval. The number of washes were varied to strip away the soft coronas and isolate the hard corona. Hundreds of proteins were adsorbed to the NPs. Some proteins were common to all isolation methods and many others were particular to the isolation method. Some qualitative trends in protein character were discerned from quantitative proteomic analyses, but more importantly, a new kind of protein corona was identified, mixed corona, in which the labile or inert nature of the protein-NP interaction is dependent upon sample history.

Early structural and functional changes in Baikal Sculpin gills exposed to suspended soot microparticles in experiment

The toxic influence of soot microparticles on terrestrial organisms has been well studied, although there is scarce data on how microparticles could affect hydrobionts. We performed a first-ever study of the short-term (5 days) impact of furnace soot (0.005 g/L) on the structural and functional features of gill cells in the Baikal Sculpin species Paracottus knerii, Dybowski, 1874. The soot samples used in the experiment were composed of small (10-100 nm) particles and larger (up to 20 μm) aggregates. The dominant fractions of the polycyclic aromatic hydrocarbons of these microparticles were phenanthrene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzofluoranthenes, benzopyrenes, indeno[1,2,3-c,d]pyrenes, and benzo[ghi]perylene. Trace element analysis of the soot detected the presence of C, S, Si, Al, Ca, K, Mg, P, and Fe. The gill condition was assessed with electron scanning, transmission, and laser confocal microscopy. Soot induces degenerative changes in the macrostructure and surface of secondary lamellae and increases mucus production in fish gills. A decrease in mitochondrial activity, an increase in reactive oxygen species production, and an increase in the frequency of programmed cell death in gill epithelium were observed under the influence of soot. In chloride cells, an induction of macroautophagy was detected. In general, the changes in fish gills after the short-term influence of soot microparticles indicate the stress of respiratory and osmotic regulation systems in fish. The data obtained are important for forming a coherent picture of the impact of soot on hydrobionts and for developing bioindication methods for evaluating the risks of their influence on aquatic ecosystems.

Energy Starvation in Daphnia magna from Exposure to a Lithium Cobalt Oxide Nanomaterial

Growing evidence across organisms points to altered energy metabolism as an adverse outcome of metal oxide nanomaterial toxicity, with a mechanism of toxicity potentially related to the redox chemistry of processes involved in energy production. Despite this evidence, the significance of this mechanism has gone unrecognized in nanotoxicology due to the field's focus on oxidative stress as a universal─but nonspecific─nanotoxicity mechanism. To further explore metabolic impacts, we determined lithium cobalt oxide's (LCO's) effects on these pathways in the model organism Daphnia magna through global gene-expression analysis using RNA-Seq and untargeted metabolomics by direct-injection mass spectrometry. Our results show that a sublethal 1 mg/L 48 h exposure of D. magna to LCO nanosheets causes significant impacts on metabolic pathways versus untreated controls, while exposure to ions released over 48 h does not. Specifically, transcriptomic analysis using DAVID indicated significant enrichment (Benjamini-adjusted p ≤0.0.5) in LCO-exposed animals for changes in pathways involved in the cellular response to starvation (25 genes), mitochondrial function (70 genes), ATP-binding (70 genes), oxidative phosphorylation (53 genes), NADH dehydrogenase activity (12 genes), and protein biosynthesis (40 genes). Metabolomic analysis using MetaboAnalyst indicated significant enrichment (γ-adjusted p <0.1) for changes in amino acid metabolism (19 metabolites) and starch, sucrose, and galactose metabolism (7 metabolites). Overlap of significantly impacted pathways by RNA-Seq and metabolomics suggests amino acid breakdown and increased sugar import for energy production. Results indicate that LCO-exposed Daphnia respond to energy starvation by altering metabolic pathways, both at the gene expression and metabolite levels. These results support altered energy production as a sensitive nanotoxicity adverse outcome for LCO exposure and suggest negative impacts on energy metabolism as an important avenue for future studies of nanotoxicity, including for other biological systems and for metal oxide nanomaterials more broadly.

Protein Fe-S Centers as a Molecular Target of Toxicity of a Complex Transition Metal Oxide Nanomaterial with Downstream Impacts on Metabolism and Growth

Oxidative stress is frequently identified as a mechanism of toxicity of nanomaterials. However, rarely have the specific underlying molecular targets responsible for these impacts been identified. We previously demonstrated significant negative impacts of transition metal oxide (TMO) lithium-ion battery cathode nanomaterial, lithium cobalt oxide (LCO), on the growth, development, hemoglobin, and heme synthesis gene expression in the larvae of a model sediment invertebrate Chironomus riparius. Here, we propose that alteration of the Fe-S protein function by LCO is a molecular initiating event leading to these changes. A 10 mg/L LCO exposure causes significant oxidation of the aconitase 4Fe-4S center after 7 d as determined from the electron paramagnetic resonance spectroscopy measurements of intact larvae and a significant reduction in the aconitase activity of larval protein after 48 h (p < 0.05). Next-generation RNA sequencing identified significant changes in the expression of genes involved in 4Fe-4S center binding, Fe-S center synthesis, iron ion binding, and metabolism for 10 mg/L LCO at 48 h (FDR-adjusted, p < 0.1). We propose an adverse outcome pathway, where the oxidation of metabolic and regulatory Fe-S centers of proteins by LCO disrupts metabolic homeostasis, which negatively impacts the growth and development, a mechanism that may apply for these conserved proteins across species and for other TMO nanomaterials.

Quantitative Mapping of Oxidative Stress Response to Lithium Cobalt Oxide Nanoparticles in Single Cells Using Multiplexed in Situ Gene Expression Analysis

Engineered nanoparticles (NPs) can negatively impact biological systems through induced generation of reactive oxygen species (ROS). Overproduced ROS cause biochemical damage and hence need to be effectively buffered by a sophisticated cellular oxidative stress response system. How this complex cellular system, which consists of multiple enzymes, responds to NP-induced ROS is largely unknown. Here, we apply a single cell analysis to quantitatively evaluate 10 key ROS responsive genes simultaneously to understand how the cell prioritizes tasks and reallocates resources in response to NP-induced oxidative stress. We focus on rainbow trout gill epithelial cells-a model cell type for environmental exposure-and their response to the massive generation of ROS induced by lithium cobalt oxide (LCO) NPs, which are extensively used as cathode materials in lithium ion batteries. Using multiplexed fluctuation localization imaging-based fluorescence in situ hybridization (fliFISH) in single cells, we found a shift in the expression of oxidative stress response genes with initial increase in genes targeting superoxide species, followed by increase in genes targeting peroxide and hydroxyl species. In contrast, Li⁺ and Co²⁺, at concentrations expected to be shed from the NPs, did not induce ROS generation but showed a potent inhibition of transcription for all 10 stress response genes. Taken together, our findings suggest a "two-hit" model for LCO NP toxicity, where the intact LCO NPs induce high levels of ROS that elicit sequential engagement of stress response genes, while the released metal ions suppress the expression of these genes. Consequently, these effects synergistically drive the exposed cells to become more vulnerable to ROS stress and damage.

TiO2 nanoparticles generate superoxide and alter gene expression in human lung cells

TiO₂ nanoparticles are widely used in consumer products and industrial applications, yet little is understood regarding how the inhalation of these nanoparticles impacts long-term health. This is especially important for the occupational safety of workers who process these materials. We used RNA sequencing to probe changes in gene expression and fluorescence microscopy to image intracellular reactive oxygen species (ROS) in human lung cells incubated with low, non-cytotoxic, concentrations of TiO₂ nanoparticles. Experiments were designed to measure changes in gene expression following an acute exposure to TiO₂ nanoparticles and changes inherited by progeny cells. We observe that TiO₂ nanoparticles lead to significant (>2000 differentially expressed genes) changes in gene expression following a 24 hour incubation. Following this acute exposure, the response dissipates with only 34 differentially expressed genes in progeny cells. The progeny cells adapt to this initial exposure, observed when re-challenged with a second acute TiO₂ nanoparticle exposure. Accompanying these changes in gene expression is the production of intracellular ROS, specifically superoxide, along with changes in oxidative stress-related genes. These experiments suggest that TiO₂ nanoparticles adapt to oxidative stress through transcriptional changes over multiple generations of cells.

Human lung cells have a multi-generational response to TiO₂ nanoparticle exposure determined by RNA-Seq and fluorescence microscopy.