New insights on the effects of ionic liquid structural changes at the gene expression level: Molecular mechanisms of toxicity in Daphnia magna

A short-term exposure to saxitoxin triggers a multitude of deleterious effects in Daphnia magna at levels deemed safe for human health

Harmful algal blooms and the toxins produced during these events are a human and environmental health concern worldwide. Saxitoxin and its derivatives are potent natural aquatic neurotoxins produced by certain freshwater cyanobacteria and marine algae species during these bloom events. Saxitoxins effects on human health are well studied, however its effects on aquatic biota are still largely unexplored. This work aims at evaluating the effects of a pulse acute exposure (24 h) of the model cladoceran Daphnia magna to 30 μg saxitoxin L-1, which corresponds to the safety guideline established by the World Health Organization (WHO) for these toxins in recreational freshwaters. Saxitoxin effects were assessed through a comprehensive array of biochemical (antioxidant enzymes activity and lipid peroxidation), genotoxicity (alkaline comet assay), neurotoxicity (total cholinesterases activity), behavioral (swimming patterns), physiological (feeding rate and heart rate), and epigenetic (total 5-mC DNA methylation) biomarkers. Exposure resulted in decreased feeding rate, heart rate, total cholinesterases activity and catalase activity. Contrarily, other antioxidant enzymes, namely glutathione-S-transferases and selenium-dependent Glutathione peroxidase had their activity increased, together with lipid peroxidation levels. The enhancement of the antioxidant enzymes was not sufficient to prevent oxidative damage, as underpinned by lipid peroxidation enhancement. Accordingly, average DNA damage level was significantly increased in STX-exposed daphnids. Total DNA 5-mC level was significantly decreased in exposed organisms. Results showed that even a short-term exposure to saxitoxin causes significant effects on critical molecular and cellular pathways and modulates swimming patterns in D. magna individuals. This study highlights sub-lethal effects caused by saxitoxin in D. magna, suggesting that these toxins may represent a marked challenge to their thriving even at a concentration deemed safe for humans by the WHO.

Miniaturizing Nanotoxicity Assays in Daphnids

The rapid progress of the modern world has resulted in new materials and products created at an accelerating pace. As such, nanoparticles have widespread applications and often find their way into the aquatic ecosystem. In the case of freshwater ecosystems, one of the commonly used bioindicators species used for pollution assessment is Daphnid magna. The Organization for Economic Co-operation and Development (OECD), and other organizations such as the European Chemicals Agency (ECHA) and Environmental Protection Agency (EPA), have set guidelines for acute toxicity testing in daphnids that are severely lacking in terms of information on the characteristics of the exposure vessel when studying the adverse effects of nanoparticles (NPs). Understanding the toxicity mechanisms of nanomaterials is imperative given the scarcity of information on their adverse effects. Furthermore, miniaturization of nanotoxicity assays can reduce the number of daphnids used, as well as the cost and nanomaterial waste, and provide results even at the individual animal level with enhanced reproducibility of testing. In this study, the impact of the exposure vessel on the observed physiological changes of daphnids was investigated for a silver nano ink. Exposures in eleven commercially available vessels; nine made of plastic and two made of glass were compared for 24 h. The effect of surface to volume ratio of the exposure vessel and the animal number or "crowding" during exposure was investigated in the context of miniaturizing biomarker assays as alternatives to traditional experimental setups in Daphnid magna. Toxicity curves showed differences depending on the vessel used, while a novel feeding rate assay and the activity of key enzymes were assessed as physiology endpoints.

Ecotoxicity studies reveal that organic cations in dicamba-derived ionic liquids can pose a greater environmental risk than the herbicide itself

The following research provides novel and relevant insights into potential environmental consequences of combination of various organic cations with commercial systemic herbicide (dicamba), in accordance with a 'herbicidal ionic liquids' (HILs) strategy. Toxicity assays of five dicamba-based HILs comprising different hydrophobic and hydrophilic cations, namely choline [CHOL][DIC], ethyl betainate [BETC2][DIC], decyl betainate [BETC10][DIC], hexadecyl betainate [BETC16][DIC] and didecyldimethylammonium [DDA][DIC]), have been tested towards bacteria (Pseudomonas putida, Escherichia coli, Bacillus subtilis), algae (Chlorella vulgaris), fresh and marine water crustaceans (Daphnia magna, Artemia franciscana). The structure of respective substituents in the cation emerged as a decisive determinant of toxicity in the case of tested species. In consequence, small ions of natural origin ([CHOL] and [BETC2]) demonstrated toxicity numerous orders of magnitude lower compared to fully synthetic [DDA]. These results emphasize the role of cations' hydrophobicity, as well as origin, in the observed acute toxic effect. Time-dependent toxicity assays also indicated that betaine-type cations comprising an ester bond can rapidly transform into less harmful substances, which can generally result in a reduction in toxicity by even several orders of magnitude. Nonetheless, these findings challenge the concept of ionic liquids with herbicidal activity and give apparent parallels to adjuvant-dependent toxicity issues recently noted in typical herbicidal formulations.

A review on aquatic toxins - Do we really know it all regarding the environmental risk posed by phytoplankton neurotoxins?

Aquatic toxins are potent natural toxins produced by certain cyanobacteria and marine algae species during harmful cyanobacterial and algal blooms (CyanoHABs and HABs, respectively). These harmful bloom events and the toxins produced during these events are a human and environmental health concern worldwide, with occurrence, frequency and severity of CyanoHABs and HABs being predicted to keep increasing due to ongoing climate change scenarios. These contexts, as well as human health consequences of some toxins produced during bloom events have been thoroughly reviewed before. Conversely, the wider picture that includes the non-human biota in the assessment of noxious effects of toxins is much less covered in the literature and barely covered by review works. Despite direct human exposure to aquatic toxins and related deleterious effects being responsible for the majority of the public attention to the blooms' problematic, it constitutes a very limited fraction of the real environmental risk posed by these toxins. The disruption of ecological and trophic interactions caused by these toxins in the aquatic biota building on deleterious effects they may induce in different species is paramount as a modulator of the overall magnitude of the environmental risk potentially involved, thus necessarily constraining the quality and efficiency of the management strategies that should be placed. In this way, this review aims at updating and consolidating current knowledge regarding the adverse effects of aquatic toxins, attempting to going beyond their main toxicity pathways in human and related models' health, i.e., also focusing on ecologically relevant model organisms. For conciseness and considering the severity in terms of documented human health risks as a reference, we restricted the detailed revision work to neurotoxic cyanotoxins and marine toxins. This comprehensive revision of the systemic effects of aquatic neurotoxins provides a broad overview of the exposure and the hazard that these compounds pose to human and environmental health. Regulatory approaches they are given worldwide, as well as (eco)toxicity data available were hence thoroughly reviewed. Critical research gaps were identified particularly regarding (i) the toxic effects other than those typical of the recognized disease/disorder each toxin causes following acute exposure in humans and also in other biota; and (ii) alternative detection tools capable of being early-warning signals for aquatic toxins occurrence and therefore provide better human and environmental safety insurance. Future directions on aquatic toxins research are discussed in face of the existent knowledge, with particular emphasis on the much-needed development and implementation of effective alternative (eco)toxicological biomarkers for these toxins. The wide-spanning approach followed herein will hopefully stimulate future research more broadly addressing the environmental hazardous potential of aquatic toxins.

Ionic liquids revolutionizing biomedicine: recent advances and emerging opportunities

Ionic liquids (ILs), due to their inherent structural tunability, outstanding miscibility behavior, and excellent electrochemical properties, have attracted significant research attention in the biomedical field. As the application of ILs in biomedicine is a rapidly emerging field, there is still a need for systematic analyses and summaries to further advance their development. This review presents a comprehensive survey on the utilization of ILs in the biomedical field. It specifically emphasizes the diverse structures and properties of ILs with their relevance in various biomedical applications. Subsequently, we summarize the mechanisms of ILs as potential drug candidates, exploring their effects on various organisms ranging from cell membranes to organelles, proteins, and nucleic acids. Furthermore, the application of ILs as extractants and catalysts in pharmaceutical engineering is introduced. In addition, we thoroughly review and analyze the applications of ILs in disease diagnosis and delivery systems. By offering an extensive analysis of recent research, our objective is to inspire new ideas and pathways for the design of innovative biomedical technologies based on ILs.

Insights into the interaction of human serum albumin with ionic liquids - Thermodynamic, spectroscopic and molecular modelling studies

Human serum albumin (HSA) effectively binds different types of low-molecular-weight compounds and thus enables their distribution in living organisms. Recently, it has been reported that the protein-ligand interactions play a crucial role in bioaccumulation processes and provide an important sorption phase, especially for ionogenic compounds. Therefore, the binding interactions of such compounds with proteins are the subject of an ongoing interest in environmental and life sciences. In this paper, the influence of some counter-ions, namely [B(CN)4]- and [C(CN)3]- on the affinity of the [IM1-12]+ towards HSA has been investigated and discussed based on experimental methods (isothermal titration calorimetry and steady-state fluorescence spectroscopy) and molecular dynamics-based computational approaches. Furthermore, the thermal stability of the resulting HSA/ligand complexes was assessed using DSC and CD spectroscopy. As an outcome of the work, it has been ascertained that the protein is able to bind simultaneously the ligands under study but in different regions of HSA. Thus, the presence in the system of [IM1-12]+ does not disturb the binding of [C(CN)3]- and [B(CN)4]-. The presented results provide important information on the presence of globular proteins and some ionogenic compounds in the distribution and bioaccumulation of ILs in the environment and living organisms.

Chronic and intergenerational toxic effects of 1-decyl-3-methylimidazolium hexafluorophosphate on the water flea, Moina macrocopa

With the increasing use and production of "green solvents" ionic liquids (ILs) and their known stability in the environment, the potential adverse effects of ILs have become a focus of research. In the present study, acute, chronic, and intergenerational toxic effects of an imidazolium-based ionic liquid, 1-decyl-3-methylimidazolium hexafluorophosphate ([Demim]PF6), on Moina macrocopa were investigated following the parental exposure. The results showed that [Demim]PF6 exhibited high toxicity to M. macrocopa, and the long-term exposure significantly inhibited the survivorship, development, and reproduction of the water flea. Furthermore, it is also observed that [Demim]PF6 induced toxic effects in the following generation of M. macrocopa, resulting in the complete cessation of reproduction in the first offspring generation, and the growth of the organisms was also significantly affected. These findings provided a novel insight into the intergenerational toxicity induced by ILs to crustaceans and suggested that these compounds pose potential risks to the aquatic ecosystem.

Toxicity of ionic liquids against earthworms (Eisenia fetida)

Ionic liquids (ILs) are widely used in frontier fields because of their highly tunable properties. Although ILs may have adverse effects on organisms, few studies have focused on their effect on earthworm gene expression. Herein we investigated the toxicity mechanism of different ILs towards Eisenia fetida using transcriptomics. Earthworms were exposed to soil containing different concentrations and types of ILs, and behavior, weight, enzymatic activity and transcriptome were analyzed. Earthworms exhibited avoidance behavior towards ILs and growth was inhibited. ILs also affected antioxidant and detoxifying enzymatic activity. These effects were concentration and alkyl chain length-dependent. Analysis of intrasample expression levels and differences in transcriptome expression levels showed good parallelism within groups and large differences between groups. Based on functional classification analysis, we speculate that toxicity mainly occurs through translation and modification of proteins and intracellular transport functions, which affect protein-related binding functions and catalytic activity. KEGG pathway analysis revealed that ILs may damage the digestive system of earthworms, among other possible pathological effects. Transcriptome analysis reveals mechanisms that cannot be observed by conventional toxicity endpoints. This is useful to evaluate the potential environmental adverse effects of the industrial use of ILs.

Toxicity of ionic liquids in marine and freshwater microorganisms and invertebrates: state of the art

The variety of applications and expected growth in ionic liquid production are raising concerns about the release of these compounds into aquatic systems. Up to date, 103 studies have provided ecotoxicological data regarding the exposure effects of Ionic Liquids towards aquatic microorganisms and invertebrate species: 61 were devoted to freshwater species (n = 28), while marine species (n = 12) were mentioned in 42. The aim of this review, by gathering published studies on ionic liquids and model aquatic organisms, was to present the toxic effects described in distinct species and to understand which are the main factors influencing the toxicity of some ionic liquids. In accordance with the most recognized pattern, freshwater species were featured in a higher number of publications than marine ones. After literature analysis, algal species were the most represented organisms in aquatic toxicity assessments. Among tested compounds, the imidazolium cations in combination with long alkyl-chain anions, showed to be the most toxic one. In analytical terms, it is not straightforward to find the undissociated compound in a natural compartment, as ionic liquids are composed of ionic components, easily subjected to dissociation. Given the aforementioned, the present review paper points out the need of increasing the number of organisms being assessed in ionic liquids toxicity assays, in order to start defining monitoring procedures. Moreover, such would allow a better understanding of ionic liquids contamination status and, also, the opportunity to remark the effectiveness of new in silico methods for the ecotoxicity assessment of this kind of substances.

Salinity fluctuation influences the toxicity of 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) to a marine diatom Phaeodactylum tricornutum

In this work, a marine diatom (Phaeodactylum tricornutum) was exposed to 1-octyl-3-methylimidazolium chloride ([C₈mim]Cl) for 96 h at three different salinities (25, 35, and 45 ‰) for investigating their interactive effects. Results showed that values of EC₁₀ and EC₅₀ at 96 h of exposure were 0.29, 1.06, 2.01 μg L^-1 and 7.21, 7.71, 7.25 mg L^-1 when the salinities were 25, 35, and 45 ‰, respectively, meaning that salinity fluctuation affected the toxicity of [C₈mim]Cl to this diatom. Changes in chlorophyll a contents and chlorophyll fluorescence parameters suggested that [C₈mim]Cl and salinity fluctuation had a significant interactive effect on the algal photosynthesis. In addition, soluble protein content and activities of antioxidant enzymes in algal cells changed significantly. Increased malondialdehyde contents indicated that the combined stresses could induce excessive production of reactive oxygen species leading to oxidative damage to the algal cells.

Machine Learning Models for Identification and Prediction of Toxic Organic Compounds Using Daphnia magna Transcriptomic Profiles

A wide range of environmental factors heavily impact aquatic ecosystems, in turn, affecting human health. Toxic organic compounds resulting from anthropogenic activity are a source of pollution in aquatic ecosystems. To evaluate these contaminants, current approaches mainly rely on acute and chronic toxicity tests, but cannot provide explicit insights into the causes of toxicity. As an alternative, genome-wide gene expression systems allow the identification of contaminants causing toxicity by monitoring the organisms' response to toxic substances. In this study, we selected 22 toxic organic compounds, classified as pesticides, herbicides, or industrial chemicals, that induce environmental problems in aquatic ecosystems and affect human-health. To identify toxic organic compounds using gene expression data from Daphnia magna, we evaluated the performance of three machine learning based feature-ranking algorithms (Learning Vector Quantization, Random Forest, and Support Vector Machines with a Linear kernel), and nine classifiers (Linear Discriminant Analysis, Classification And Regression Trees, K-nearest neighbors, Support Vector Machines with a Linear kernel, Random Forest, Boosted C5.0, Gradient Boosting Machine, eXtreme Gradient Boosting with tree, and eXtreme Gradient Boosting with DART booster). Our analysis revealed that a combination of feature selection based on feature-ranking and a random forest classification algorithm had the best model performance, with an accuracy of 95.7%. This is a preliminary study to establish a model for the monitoring of aquatic toxic substances by machine learning. This model could be an effective tool to manage contaminants and toxic organic compounds in aquatic systems.

Carotenoid Production from Microalgae: The Portuguese Scenario

Microalgae have an outstanding capacity to efficiently produce value-added compounds. They have been inspiring researchers worldwide to develop a blue biorefinery, supporting the development of the bioeconomy, tackling the environmental crisis, and mitigating the depletion of natural resources. In this review, the characteristics of the carotenoids produced by microalgae are presented and the downstream processes developed to recover and purify them are analyzed, considering their main applications. The ongoing activities and initiatives taking place in Portugal regarding not only research, but also industrialization under the blue biorefinery concept are also discussed. The situation reported here shows that new techniques must be developed to make microalgae production more competitive. Downstream pigment purification technologies must be developed as they may have a considerable impact on the economic viability of the process. Government incentives are needed to encourage a constructive interaction between academics and businesses in order to develop a biorefinery that focuses on high-grade chemicals.

Interaction of ionic liquids with human serum albumin in the view of bioconcentration: a preliminary study

Bioaccumulation potential is critical in PBT and risk assessment of chemicals. However, for ionic liquids (ILs), this aspect remains neglected. It is especially important to fill this gap, because for this group of compounds, existing data confirm their risk of being environmentally persistent and toxicity. Moreover, considering preliminary reports on the interactions of ILs with lipids, it may be assumed that ILs have a higher potential for bioaccumulation than indicated by previous estimations built upon octanol–water partition coefficients. Moreover, the bioconcentration of ionizable chemical compounds may also be strongly related to plasma protein contents. Therefore, in this work, the affinity of a set of imidazolium cations and organic anions, and their combination to human serum albumin (HSA) was determined. The obtained results reveal that both cations and anions can be strongly bound to HSA, and blood proteins might play an important role in overall bioaccumulation. Furthermore, it was observed that HSA binding properties towards IL cations depend on the hydrophobicity of cations. The obtained data also provide indication that cation–anion interaction may affect ILs ions affinity to HSA.

Molecular response mechanisms of silkworm (Bombyx mori L.) to the toxicity of 1-octyl-3-methylimidazole chloride based on transcriptome analysis of midguts and silk glands

In a previous study, silkworm larvae were used as a novel model to assess the biotoxicity of ILs, which showed that ILs could cause significant physiological and biochemical changes in midguts and silk glands of the larvae, and result in the death of larvae. In order to investigate the toxicity of 1-octyl-3-methylimidazole chloride ([C₈mim]Cl) to the larvae at molecular level, RNA-sequencing technology was used to construct transcriptomic profiles of midguts and silk glands in this work. Results showed that a lot of differentially expressed genes (DEGs) were effectively screened out through bioinformatics software based on the transcriptome data and reference genome. To give more detail, 5118 and 2211 DEGs (926 and 822 DEGs) were obtained in the midguts (silk glands) when the larvae were exposed to [C₈mim]Cl for 6 and 12 h, respectively, relative to the controls. In addition, gene ontology (GO) analysis suggested that the DEGs could be divided into three categories (i.e., biological process, cellular component, and molecular function), and were involved in multiple organelle functions and complex biological processes. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that the DEGs were enriched in a variety of pathways, such as signal transduction, apoptosis, glycolysis, peroxisome, autophagy, hippo signaling pathway, arginine and proline metabolism. Results of quantitative real-time PCR and histopathological observation indicated that molecular mechanism of the larvae against [C₈mim]Cl toxicology may be attributed to cell apoptosis regulation via both the mitochondrial pathway and the death receptor-initiated pathway. Thus, these results provided useful data for exploring the toxicity of ILs to insects at molecular level.

Chemical safety assessment of transformation products of landfill leachate formed during the Fenton process

Organic chemicals identified in raw landfill leachate (LL) and their transformation products (TPs), formed during Fenton treatment, were analyzed for chemical safety following REACH guidelines. The raw LL was located in the metropolitan region of Campina Grande, in northeast Brazil. We elucidated 197 unique chemical structures, including 154 compounds that were present in raw LL and 82 compounds that were detected in the treated LL, totaling 39 persistent compounds and 43 TPs. In silico models were developed to identify and prioritize the potential level of hazard/risk these compounds pose to the environment and society. The models revealed that the Fenton process improved the biodegradability of TPs. Still, a slight increase in ecotoxicological effects was observed among the compounds in treated LL compared with those present in raw LL. No differences were observed for aryl hydrocarbon receptor (AhR) and antioxidant response element (ARE) mutagenicity. Similar behavior among both raw and treated LL samples was observed for biodegradability; Tetrahymena pyriformis, Daphnia magna, Pimephales promelas and ARE, AhR, and Ames mutagenicity. Overall, our results suggest that raw and treated LL samples have similar activity profiles for all endpoints other than biodegradability.

Total Triterpenoid Extraction from Inonotus Obliquus Using Ionic Liquids and Separation of Potential Lactate Dehydrogenase Inhibitors via Ultrafiltration High-Speed Countercurrent Chromatography

Extracts of the fungus Inonotus obliquus exhibit cytotoxic properties against different cancers; hence, this fungal species has been extensively studied. This study aimed to extract total triterpenoids from Inonotus obliquus using ionic liquids (ILs) and separate potential lactate dehydrogenase (LDH) inhibitors via ultrafiltration (UF)-high-speed countercurrent chromatography (HSCCC). Total triterpenoids from Inonotus obliquus were extracted by performing a single-factor experiment and employing a central composite design via ultrasonic-assisted extraction (UAE) and heat-assisted extraction (HAE). The extract was composed of 1-butyl-3-methylimidazolium bromide as the IL and methanol as the dispersant. Ultrafiltration-liquid chromatography (UF-LC) was used to rapidly scan the LDH inhibitors and betulin and lanosterol were identified as potential inhibitors. To obtain these target compounds, betulin and lanosterol with the purities of 95.9% and 97.8% were isolated from HSCCC within 120 min. Their structures were identified using several techniques, among which IL-HAE was fast and effective. This study reports the extraction of triterpenoids from Inonotus obliquus by IL for the first time. Collectively, the findings demonstrate that UF-LC is an effective tool for screening potential LDH inhibitors from crude extracts of I. obliquus and may help to identify bioactive substances against myocardial infarction, whereas high-purity compounds can be separated via UF-HSCCC.