The role of high-throughput screening in ecotoxicology and engineered nanomaterials

Effect of aging of microplastics on gene expression levels of the marine mussel Mytilus edulis: Comparison in vitro/in vivo exposures

In the present study, effects of aging MPs of polyethylene (PE) were investigated in the marine mussel Mytilus edulis, commonly used as bioindicator of aquatic ecosystem, using both in vitro and in vivo exposures, using concentrations found in marine waters (0.008, 10 and 100 μg.L-1). Changes in gene expression levels implicated in detoxification, immune system, cytoskeletton and cell cycle control were evaluated by quantitative RT-qPCR. Results demonstrated differential expression levels depending upon the state of plastic degradation (aged vs non-aged) and way of exposure (vitro vs vivo). This study highlighted the interest of using molecular biomarkers based on analysis of gene expression pattern in an ecotoxicological context that gives indication of relative slight changes between tested conditions as compared to other biochemical approaches (e.g. enzymatic activities). In addition, in vitro analysis could be used to generate large amount of data as regards to the toxicological effects of MPs.

Effect of size continuum from nanoplastics to microplastics on marine mussel Mytilus edulis: Comparison in vitro/in vivo exposure scenarios

For several decades, plastic has been a global threat in terms of pollution. Plastic polymers, when introduce in the aquatic environment, are exposed to fragmentation processes into microplastics (MPs) and nanoplastics (NPs) which could potentially interact with living organisms. The objective of this work was to study the effects of plastic particles representative of those found in the environment, on the marine mussels Mytilus edulis, under two exposure scenarios: in vivo and in vitro. Whole mussels or cultured hemocytes were exposed for 24 h to NPs and MPs generated from macro-sized plastics collected in the field, but also to reference NPs, at concentrations found in the environment: 0.08, 10 μg and 100 μg·L^-1. Results showed that immune response was only activated when mussels were exposed in vivo. However, cytotoxicity (hemocyte mortality) and genotoxicity (DNA damage) parameters were induced after both types of exposure, but in a dose-dependent manner after in vitro hemocyte exposure to all tested plastic conditions. These results indicate that in vitro approaches could be considered as potential predictors of in vivo exposures.

High-throughput screening paradigms in ecotoxicity testing: Emerging prospects and ongoing challenges

The rapidly increasing number of new production chemicals coupled with stringent implementation of global chemical management programs necessities a paradigm shift towards boarder uses of low-cost and high-throughput ecotoxicity testing strategies as well as deeper understanding of cellular and sub-cellular mechanisms of ecotoxicity that can be used in effective risk assessment. The latter will require automated acquisition of biological data, new capabilities for big data analysis as well as computational simulations capable of translating new data into in vivo relevance. However, very few efforts have been so far devoted into the development of automated bioanalytical systems in ecotoxicology. This is in stark contrast to standardized and high-throughput chemical screening and prioritization routines found in modern drug discovery pipelines. As a result, the high-throughput and high-content data acquisition in ecotoxicology is still in its infancy with limited examples focused on cell-free and cell-based assays. In this work we outline recent developments and emerging prospects of high-throughput bioanalytical approaches in ecotoxicology that reach beyond in vitro biotests. We discuss future importance of automated quantitative data acquisition for cell-free, cell-based as well as developments in phytotoxicity and in vivo biotests utilizing small aquatic model organisms. We also discuss recent innovations such as organs-on-a-chip technologies and existing challenges for emerging high-throughput ecotoxicity testing strategies. Lastly, we provide seminal examples of the small number of successful high-throughput implementations that have been employed in prioritization of chemicals and accelerated environmental risk assessment.

Present and pioneer methods of early detection of food borne pathogens

Food-borne pathogens are a severe threat to human illness and death world-wide. Researchers have reported more than 250 food-borne diseases. Most of these are infections caused by a wide variety of bacteria, viruses, and parasites. It has a significant economic impact also. Detection of pathogenic microbes is thus essential for food safety. Such identification techniques could meet the following parameters viz., the accuracy of detection techniques that are quick, efficient, economical, highly sensitive, specific, and non-labor intensive. The various available methods for detecting food pathogens are classified into different groups, each having its advantages and disadvantages. The conventional methods are usually the first choice of detection even though they are laborious. Modern techniques such as biosensors, immunological assays, and macromolecule-based (nucleic acid) methods are being developed and refined to overcome traditional methods' limitations. Early detection of pathogens and secure food safety at each stage of food processing to storage, utilizing improved methodologies are mandatory. This review summarizes the deadly food pathogens leading to significant outbreaks and discusses the importance of early detection methods and advanced detection methods in comparison.

Genotoxic assessment of cerium and magnesium nanoparticles and their ionic forms in Eisenia hortensis coelomocytes by alkaline comet assay

The present study aimed to evaluate the genotoxic potential of cerium oxide (CeO₂ ), magnesium oxide (MgO) nanoparticles and their ionic forms by alkaline comet assay. Eisenia hortensis were exposed to different series of concentrations (25, 50, 100, 200, and 400 μg/ml) of chemicals for 48 h to find LC₅₀ . The LC₅₀ for MgO and CeO₂ NPs were 70 and 80 μg/ml. Whereas, the LC₅₀ for their ionic forms were 50 and 70 μg/ml. To assess the potential DNA damage caused by the chosen chemicals, E. hortensis was further exposed for 48 h to the following concentrations, based on their respective LC_50s : LC_50/2 , LC⁵⁰ , and 2xLC₅₀ . Comet scores demonstrated the significant increase (p < 0.05) in DNA damage at all concentrations, both for NPs and ionic forms in a concentration-dependent manner. Findings of the present study revealed the genotoxic effects of CeO₂ NPs, MgO NPs and their ionic forms on E. hortensis.

Assessing Fish Immunotoxicity by Means of In Vitro Assays: Are We There Yet?

There is growing awareness that a range of environmental chemicals target the immune system of fish and may compromise the resistance towards infectious pathogens. Existing concepts to assess chemical hazards to fish, however, do not consider immunotoxicity. Over recent years, the application of in vitro assays for ecotoxicological hazard assessment has gained momentum, what leads to the question whether in vitro assays using piscine immune cells might be suitable to evaluate immunotoxic potentials of environmental chemicals to fish. In vitro systems using primary immune cells or immune cells lines have been established from a wide array of fish species and basically from all immune tissues, and in principal these assays should be able to detect chemical impacts on diverse immune functions. In fact, in vitro assays were found to be a valuable tool in investigating the mechanisms and modes of action through which environmental agents interfere with immune cell functions. However, at the current state of knowledge the usefulness of these assays for immunotoxicity screening in the context of chemical hazard assessment appears questionable. This is mainly due to a lack of assay standardization, and an insufficient knowledge of assay performance with respect to false positive or false negative signals for the different toxicant groups and different immune functions. Also the predictivity of the in vitro immunotoxicity assays for the in vivo immunotoxic response of fishes is uncertain. In conclusion, the currently available database is too limited to support the routine application of piscine in vitro assays as screening tool for assessing immunotoxic potentials of environmental chemicals to fish.

Is cell culture a suitable tool for the evaluation of micro- and nanoplastics ecotoxicity?

Plastic particles have been described in aquatic ecosystems worldwide. An increasing number of studies have tried to evaluate the toxic impacts of microplastics (1-5000 µm) but also nanoplastics (<1 µm) in marine and freshwater organisms. However, the wide variety of plastic particles characteristics such as various sizes, shapes, functionalization or types of polymer, makes it difficult to evaluate their impact with regular ecotoxicity testing. In this context, cell culture, mainly used in human toxicology, could be a promising tool to evaluate micro- and nanoplastics toxicity with a wide diversity of conditions allowing to generate a large set of data. This review presents the current research on micro and nanoplastics using cell culture of marine and freshwater organisms, describes the limitations of cell culture tool and defines whether this tool can be considered as a relevant alternative strategy for ecotoxic evaluation of micro and nanoplastics especially for future regulatory needs. Articles using specifically cell culture tool from aquatic organisms such as fish or bivalves were identified. The majority evaluated the toxicity of polystyrene nanobeads on immune parameters, oxidative stress or DNA damage in fish cells. Although most of the papers characterized nanoplastic particles into the cell culture media, the relevance of testing conditions is not always clear. The development of cell culture can offer many opportunities for the evaluation of plastic particles' cellular impacts, but more research is needed to develop relevant culture models, on various aquatic organisms, and with consideration of abiotic parameters especially composition of cell culture media for nanoplastic evaluation.

Biocompatible functionalisation of nanoclays for improved environmental remediation

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems with detrimental implications for ecosystem recovery. Here we critically review the pros and cons of functionalised nanoclays and provide new perspectives on the synthesis of environmentally friendly varieties. Particular focus is given to finding alternatives to conventional surfactants used in modified nanoclay products, and to exploring strategies in synthesising nanoclay-supported metal and metal oxide nanoparticles. A large number of promising nanoclay-based sorbents are yet to satisfy environmental biocompatibility in situ but opportunities are there to tailor them to produce "biocompatible" or regenerative/reusable materials.

High-throughput COPAS assay for screening of developmental and reproductive toxicity of nanoparticles using the nematode Caenorhabditis elegans

With the rapid advancement and numerous applications of engineered nanomaterials (ENMs) in science and technology, their effects on animal health, environment and safety should be considered carefully. However, quick assessment of their effects on developmental and reproductive health and an understanding of how they cause such adverse toxic effects remain challenging, because of the fast-growing number of ENMs and the limitations of the different toxicity assays currently in use as well as lack of suitable animal model systems. In this study, we performed a high-throughput complex object parametric analyzer and sorter (COPAS) assay for assessing the developmental and reproductive toxicity of ENMs using Caenorhabditis elegans and provide descriptions of the data and their subsequent analysis. The results showed significant reproductive and developmental toxicity potential of different ENMs. We assessed the usefulness of this method in terms of error-free data, user-friendliness and results being consistent with those of visual, molecular and cellular studies. Moreover, the COPAS Biosort system could be used on a larger scale to screen thousands of chemicals, drugs, pharmaceuticals and ENMs. This study also indicates that the COPAS-based high-throughput screening system is highly reliable for the assessment of toxicity and health risks of NMs.

Investigating the establishment of primary cultures of hemocytes from Mytilus edulis

Anthropogenic influences on the environment have been become a focal point for many social and political endeavors. With an ever-increasing rate of new contaminants being introduced into the environment every year, regulatory policies have begun to shift to prevention rather than mitigation. However, current in vivo testing strategies, in addition to ethical considerations, are too expensive and time consuming to adequately screen potential contaminants within a realistic timeframe. As a result, in vitro testing on cell cultures has been identified as an ideal alternative testing strategy for emerging contaminants. In the context of ecotoxicology, in vitro testing has had limited use particularly with marine invertebrates like the marine mussel Mytilus edulis mainly due to difficulties in establishing longer term cell cultures and cell lines. The aim of this study was to define an optimal technique (extraction and maintenance) for establishing a primary cell culture on M. edulis hemocytes that could be used for screening contaminants.

In vitro assessment of sex steroids and related compounds in water and sediments - a critical review

Detection of endocrine disrupting compounds in water and sediment samples has gained much importance since the evidence of their effects was reported in aquatic ecosystems in the 1990s. The aim of this review is to highlight the advances made in the field of in vitro analysis for the detection of hormonally active compounds with estrogenic, androgenic and progestogenic effects in water and sediment samples. In vitro assays have been developed from yeast, mammalian and in a few cases from fish cells. These assays are based either on the hormone-mediated proliferation of sensitive cell lines or on the hormone-mediated expression of reporter genes. In vitro assays in combination with various sample enrichment methods have been used with limits of detection as low as 0.0027 ng L^-1 in water, and 0.0026 ng g^-1 in sediments for estrogenicity, 0.1 ng L^-1 in water, and 0.5 ng g^-1 in sediments for androgenicity, and 5 ng L^-1 in water for progestogenicity expressed as equivalent concentrations of standard reference compounds of 17β-estradiol, dihydrotestosterone and progesterone, respectively. The experimental results and limits of quantification, however, are influenced by the methods of sample collection, preparation, and individual laboratory practices.