Deep Learning-Based Automatic Duckweed Counting Using StarDist and Its Application on Measuring Growth Inhibition Potential of Rare Earth Elements as Contaminants of Emerging Concerns.

In recent years, there have been efforts to utilize surface water as a power source, material, and food. However, these efforts are impeded due to the vast amounts of contaminants and emerging contaminants introduced by anthropogenic activities. Herbicides such as Glyphosate and Glufosinate are commonly known to contaminate surface water through agricultural industries. In contrast, some emerging contaminants, such as rare earth elements, have started to enter the surface water from the production and waste of electronic products. Duckweeds are angiosperms from the Lemnaceae family and have been used for toxicity tests in aquatic environments, mainly those from the genus Lemna, and have been approved by OECD. In this study, we used duckweed from the genus Wolffia, which is smaller and considered a good indicator of metal pollutants in the aquatic environment. The growth rate of duckweed is the most common endpoint in observing pollutant toxicity. In order to observe and mark the fronds automatically, we used StarDist, a machine learning-based tool. StarDist is available as a plugin in ImageJ, simplifying and assisting the counting process. Python also helps arrange, manage, and calculate the inhibition percentage after duckweeds are exposed to contaminants. The toxicity test results showed Dysprosium to be the most toxic, with an IC50 value of 14.6 ppm, and Samarium as the least toxic, with an IC50 value of 279.4 ppm. In summary, we can provide a workflow for automatic frond counting using StarDist integrated with ImageJ and Python to simplify the detection, counting, data management, and calculation process.

Ractopamine at the Center of Decades-Long Scientific and Legal Disputes: A Lesson on Benefits, Safety Issues, and Conflicts.

Ractopamine (RAC) is a synthetic phenethanolamine, ß-adrenergic agonist used as a feed additive to develop leanness and increase feed conversion efficiency in different farm animals. While RAC has been authorized as a feed additive for pigs and cattle in a limited number of countries, a great majority of jurisdictions, including the European Union (EU), China, Russia, and Taiwan, have banned its use on safety grounds. RAC has been under long scientific and political discussion as a controversial antibiotic as a feed additive. Here, we will present significant information on RAC regarding its application, detection methods, conflicts, and legal divisions that play a major role in controversial deadlock and why this issue warrants the attention of scientists, agriculturists, environmentalists, and health advocates. In this review, we highlight the potential toxicities of RAC on aquatic animals to emphasize scientific evidence and reports on the potentially harmful effects of RAC on the aquatic environment and human health.

Physiological Effects of Neonicotinoid Insecticides on Non-Target Aquatic Animals-An Updated Review.

In this paper, we review the effects of large-scale neonicotinoid contaminations in the aquatic environment on non-target aquatic invertebrate and vertebrate species. These aquatic species are the fauna widely exposed to environmental changes and chemical accumulation in bodies of water. Neonicotinoids are insecticides that target the nicotinic type acetylcholine receptors (nAChRs) in the central nervous systems (CNS) and are considered selective neurotoxins for insects. However, studies on their physiologic impacts and interactions with non-target species are limited. In researches dedicated to exploring physiologic and toxic outcomes of neonicotinoids, studies relating to the effects on vertebrate species represent a minority case compared to invertebrate species. For aquatic species, the known effects of neonicotinoids are described in the level of organismal, behavioral, genetic and physiologic toxicities. Toxicological studies were reported based on the environment of bodies of water, temperature, salinity and several other factors. There exists a knowledge gap on the relationship between toxicity outcomes to regulatory risk valuation. It has been a general observation among studies that neonicotinoid insecticides demonstrate significant toxicity to an extensive variety of invertebrates. Comprehensive analysis of data points to a generalization that field-realistic and laboratory exposures could result in different or non-comparable results in some cases. Aquatic invertebrates perform important roles in balancing a healthy ecosystem, thus rapid screening strategies are necessary to verify physiologic and toxicological impacts. So far, much of the studies describing field tests on non-target species are inadequate and in many cases, obsolete. Considering the current literature, this review addresses important information gaps relating to the impacts of neonicotinoids on the environment and spring forward policies, avoiding adverse biological and ecological effects on a range of non-target aquatic species which might further impair the whole of the aquatic ecological web.

An Update Report on the Biosafety and Potential Toxicity of Fullerene-Based Nanomaterials toward Aquatic Animals.

Fullerene molecules are composed of carbon in the form of a hollow sphere, tube, or ellipsoid. Since their discovery in 1985, they have gained a lot of attention in many science fields. The unique carbon cage structure of fullerene provides immense scope for derivatization, rendering potential for various industrial applications. Thus, the prospective applications of fullerenes have led to assorted fullerene derivatives. In addition, their unique chemical structure also eases them to be synthesized through various kinds of conjugating techniques, where fullerene can be located either on the backbone or the branch chain. In this review, we have compiled the toxicity and biosafety aspects of fullerene in aquatic organisms since the frequent use of fullerene is likely to come in contact and interact with the aquatic environment and aquatic organisms. According to the current understanding, waterborne exposure to fullerene-based nanomaterials indeed triggers toxicities at cellular, organic, molecular, and neurobehavioral levels.

Sub-lethal Camphor Exposure Triggers Oxidative Stress, Cardiotoxicity, and Cardiac Physiology Alterations in Zebrafish Embryos.

Camphor is a terpene ketone with aromatic and volatile properties in nature derived from the bark of Cinnamomum camphora or synthesized from turpentine. Camphor exhibits various biological properties such as anti-microbial, anti-viral, anti-coccidial, and anti-cancer. It is also used as a form of topical medication for skin irritation, joint pain, and as a relief for itching from insect bites. However, even though the high dose of camphor has been documented to be toxic/lethal in humans in different studies, camphor's developmental toxicity has not yet been explored, and its extensive mechanism of action is still unclear. In the present study, we aimed to assess the toxic effects of camphor in zebrafish embryos in the initial developmental stages. The obtained results demonstrated that a sub-lethal dose of camphor caused a decrease in hatching rate, body length, and substantial elevation in malformation rate on zebrafish embryos. On further observation, in the following time frame, curved body and pericardial edema of zebrafish were also observed. Furthermore, exposure to a sub-lethal dose of camphor was also able to trigger cardiotoxicity in zebrafish larvae. Later, on subsequent biochemical analysis, it was found that the antioxidant capacity inhibition and oxidative stress elevation that occurred after camphor exposure might be associated with the inhibition of total superoxide dismutase (SOD) activity and an increase in reactive oxygen species (ROS) and malondialdehyde (MDA) concentration. In addition, compared to the control group, several apoptotic cells in treated zebrafish were also found to be elevated. Finally, after further investigation on marker gene expressions, we conclude that the developmental toxicity of camphor exposure might be associated with apoptosis elevation and oxidative stress. Taken together, the current study provides a better understanding of the developmental toxicity of camphor on zebrafish, a promising alternative animal model to assess the developmental toxicity of chemical compounds.

Comparison of the chronic toxicities of graphene and graphene oxide toward adult zebrafish by using biochemical and phenomic approaches.

Graphene (GR) and graphene oxide (GO) are widely being used as promising candidates for biomedical applications, as well as for bio-sensing, drug delivery, and anticancer therapy. However, their undesirable side effects make it necessary to assess further the toxicity and safety of using these materials. The main objective of the current study was to investigate the toxicities of GR and GO in predicted environmental relevant concentrations in adult zebrafish (Danio rerio), particularly on their behaviors, and conducted biochemical assays to elucidate the possible mechanism that underlies their toxicities. Zebrafish was chronically (∼14 days) exposed to two different doses of GR (0.1 and 0.5 ppm) or GO (0.1 and 1 ppm). At 14 ± 1 days, a battery of behavioral tests was conducted, followed by enzyme-linked immunosorbent assays (ELISA) test on the following day to inspect the alterations in antioxidant activity, oxidative stress, and neurotransmitters in the treated zebrafish brain. An alteration in predator avoidance behavior was observed in all treated groups, while GR-treated fish exhibited abnormal exploratory behavior. Furthermore, altered locomotor activity was displayed by most of the treated groups, except for the high concentration of the GR group. From the ELISA results, we discovered a high concentration of GR exposure significantly decreased several neurotransmitters and cortisol levels. Meanwhile, elevated reactive oxygen species (ROS) were displayed by the group treated with low and high doses of GR and GO, respectively. These significant changes would possibly affect zebrafish behaviors and might suggest the potential toxicity from GR and GO exposures. To sum up, the present study presented new evidence for the effects of GR and GO in zebrafish behavioral dysregulation. We hope these assessments can contribute to our understanding of graphene and graphene oxide biosafety.

Evaluation of the Adverse Effects of Chronic Exposure to Donepezil (An Acetylcholinesterase Inhibitor) in Adult Zebrafish by Behavioral and Biochemical Assessments.

Donepezil (DPZ) is an acetylcholinesterase inhibitor used for the clinical treatment of mild cognitive impairment. However, DPZ has been reported to have adverse effects, including causing abnormal cardiac rhythm, insomnia, vomiting, and muscle cramps. However, the existence of these effects in subjects without Dementia is unknown. In this study, we use zebrafish to conduct a deeper analysis of the potential adverse effects of DPZ on the short-term memory and behaviors of normal zebrafish by performing multiple behavioral and biochemical assays. Adult zebrafish were exposed to 1 ppm and 2.5 ppm of DPZ. From the results, DPZ caused a slight improvement in the short-term memory of zebrafish and induced significant elevation in aggressiveness, while the novel tank and shoaling tests revealed anxiolytic-like behavior to be caused by DPZ. Furthermore, zebrafish circadian locomotor activity displayed a higher reduction of locomotion and abnormal movement orientation in both low- and high-dose groups, compared to the control group. Biomarker assays revealed that these alterations were associated with an elevation of oxytocin and a reduction of cortisol levels in the brain. Moreover, the significant increases in reactive oxygen species (ROS) and malondialdehyde (MDA) levels in muscle tissue suggest DPZ exposure induced muscle tissue oxidative stress and muscle weakness, which may underlie the locomotor activity impairment. In conclusion, we show, for the first time, that chronic waterborne exposure to DPZ can severely induce adverse effects on normal zebrafish in a dose-dependent manner. These unexpected adverse effects on behavioral alteration should be carefully addressed in future studies considering DPZ conducted on zebrafish or other animals.

An Updated Review of Toxicity Effect of the Rare Earth Elements (REEs) on Aquatic Organisms.

Rare earth elements (REEs) or "technology metals" were coined by the U.S. Department of Energy, a group of seventeen elements found in the Earth's crust. These chemical elements are vital and irreplaceable to the world of technology owing to their unique physical, chemical, and light-emitting properties, all of which are beneficial in modern healthcare, telecommunication, and defense. Rare earth elements are relatively abundant in Earth's crust, with critical qualities to the device performance. The reuse and recycling of rare earth elements through different technologies can minimize impacts on the environment; however, there is insufficient data about their biological, bioaccumulation, and health effects. The increasing usage of rare earth elements has raised concern about environmental toxicity, which may further cause harmful effects on human health. The study aims to review the toxicity analysis of these rare earth elements concerning aquatic biota, considering it to be the sensitive indicator of the environment. Based on the limited reports of REE effects, the review highlights the need for more detailed studies on the hormetic effects of REEs. Aquatic biota is a cheap, robust, and efficient platform to study REEs' toxicity, mobility of REEs, and biomagnification in water bodies. REEs' diverse effects on aquatic life forms have been observed due to the lack of safety limits and extensive use in the various sectors. In accordance with the available data, we have put in efforts to compile all the relevant research results in this paper related to the topic "toxicity effect of REEs on aquatic life".

An Overview of Methods for Cardiac Rhythm Detection in Zebrafish.

The heart is the most important muscular organ of the cardiovascular system, which pumps blood and circulates, supplying oxygen and nutrients to peripheral tissues. Zebrafish have been widely explored in cardiotoxicity research. For example, the zebrafish embryo has been used as a human heart model due to its body transparency, surviving several days without circulation, and facilitating mutant identification to recapitulate human diseases. On the other hand, adult zebrafish can exhibit the amazing regenerative heart muscle capacity, while adult mammalian hearts lack this potential. This review paper offers a brief description of the major methodologies used to detect zebrafish cardiac rhythm at both embryonic and adult stages. The dynamic pixel change method was mostly performed for the embryonic stage. Other techniques, such as kymography, laser confocal microscopy, artificial intelligence, and electrocardiography (ECG) have also been applied to study heartbeat in zebrafish embryos. Nevertheless, ECG is widely used for heartbeat detection in adult zebrafish since ECG waveforms' similarity between zebrafish and humans is prominent. High-frequency ultrasound imaging (echocardiography) and modern electronic sensor tag also have been proposed. Despite the fact that each method has its benefits and limitations, it is proved that zebrafish have become a promising animal model for human cardiovascular disease, drug pharmaceutical, and toxicological research. Using those tools, we conclude that zebrafish behaviors as an excellent small animal model to perform real-time monitoring for the developmental heart process with transparent body appearance, to conduct the in vivo cardiovascular performance and gene function assays, as well as to perform high-throughput/high content drug screening.

Multiple Screening of Pesticides Toxicity in Zebrafish and Daphnia Based on Locomotor Activity Alterations.

Pesticides are widely used to eradicate insects, weed species, and fungi in agriculture. The half-lives of some pesticides are relatively long and may have the dire potential to induce adverse effects when released into the soil, terrestrial and aquatic systems. To assess the potential adverse effects of pesticide pollution in the aquatic environment, zebrafish (Danio rerio) and Daphnia magna are two excellent animal models because of their transparent bodies, relatively short development processes, and well-established genetic information. Moreover, they are also suitable for performing high-throughput toxicity assays. In this study, we used both zebrafish larvae and water flea daphnia neonates as a model system to explore and compare the potential toxicity by monitoring locomotor activity. Tested animals were exposed to 12 various types of pesticides (three fungicides and 9 insecticides) for 24 h and their corresponding locomotor activities, in terms of distance traveled, burst movement, and rotation were quantified. By adapting principal component analysis (PCA) and hierarchical clustering analysis, we were able to minimize data complexity and compare pesticide toxicity based on locomotor activity for zebrafish and daphnia. Results showed distinct locomotor activity alteration patterns between zebrafish and daphnia towards pesticide exposure. The majority of pesticides tested in this study induced locomotor hypo-activity in daphnia neonates but triggered locomotor hyper-activity in zebrafish larvae. According to our PCA and clustering results, the toxicity for 12 pesticides was grouped into two major groups based on all locomotor activity endpoints collected from both zebrafish and daphnia. In conclusion, all pesticides resulted in swimming alterations in both animal models by either producing hypo-activity, hyperactivity, or other changes in swimming patterns. In addition, zebrafish and daphnia displayed distinct sensitivity and response against different pesticides, and the combinational analysis approach by using a phenomic approach to combine data collected from zebrafish and daphnia provided better resolution for toxicological assessment.

Toxicity Studies on Graphene-Based Nanomaterials in Aquatic Organisms: Current Understanding.

Graphene and its oxide are nanomaterials considered currently to be very promising because of their great potential applications in various industries. The exceptional physiochemical properties of graphene, particularly thermal conductivity, electron mobility, high surface area, and mechanical strength, promise development of novel or enhanced technologies in industries. The diverse applications of graphene and graphene oxide (GO) include energy storage, sensors, generators, light processing, electronics, and targeted drug delivery. However, the extensive use and exposure to graphene and GO might pose a great threat to living organisms and ultimately to human health. The toxicity data of graphene and GO is still insufficient to point out its side effects to different living organisms. Their accumulation in the aquatic environment might create complex problems in aquatic food chains and aquatic habitats leading to debilitating health effects in humans. The potential toxic effects of graphene and GO are not fully understood. However, they have been reported to cause agglomeration, long-term persistence, and toxic effects penetrating cell membrane and interacting with cellular components. In this review paper, we have primarily focused on the toxic effects of graphene and GO caused on aquatic invertebrates and fish (cell line and organisms). Here, we aim to point out the current understanding and knowledge gaps of graphene and GO toxicity.

Expression and Purification of Recombinant GHK Tripeptides Are Able to Protect against Acute Cardiotoxicity from Exposure to Waterborne-Copper in Zebrafish.

In this study, an alternative method is developed to replace chemical synthesis to produce glycyl-histidyl-lysine (GHK) tripeptides with a bacterial fermentation system. The target GHK tripeptides are cloned into expression plasmids carrying histidine-glutathione-S-transferase (GST) double tags and TEV (tobacco etch virus) cleavage sites at the N-terminus. After overexpression in Escherichia coli (E. coli) BL21 cells, the recombinant proteins are purified and recovered by high-pressure liquid chromatography (HPLC). UV-vis absorption spectroscopy was used to investigate the chemical and biological properties of the recombinant GHK tripeptides. The results demonstrated that one recombinant GHK tripeptide can bind one copper ion to form a GHK-Cu complex with high affinity, and the recombinant GHK peptide to copper ion ratio is 1:1. X-ray absorption near-edge spectroscopy (XANES) of the copper ions indicated that the oxidation state of copper in the recombinant GHK-Cu complexes here was Cu(II). All of the optical spectrum evidence suggests that the recombinant GHK tripeptide appears to possess the same biophysical and biochemical features as the GHK tripeptide isolated from human plasma. Due to the high binding affinity of GHK tripeptides to copper ions, we used zebrafish as an in vivo model to elucidate whether recombinant GHK tripeptides possess detoxification potential against the cardiotoxicity raised by waterborne Cu(II) exposure. Here, exposure to Cu(II) induced bradycardia and heartbeat irregularity in zebrafish larvae; however, the administration of GHK tripeptides could rescue those experiencing cardiotoxicity, even at the lowest concentration of 1 nM, where the GHK-Cu complex minimized CuSO4-induced cardiotoxicity effects at a GHK:Cu ratio of 1:10. On the other hand, copper and the combination with the GHK tripeptide did not significantly alter other cardiovascular parameters, including stroke volume, ejection fraction, and fractional shortening. Meanwhile, the heart rate and cardiac output were boosted after exposure with 1 nM of GHK peptides. In this study, recombinant GHK tripeptide expression was performed, along with purification and chemical property characterization, which revealed a potent cardiotoxicity protection function in vivo with zebrafish for the first time.

Potential Toxicity of Iron Oxide Magnetic Nanoparticles: A Review.

The noteworthy intensification in the development of nanotechnology has led to the development of various types of nanoparticles. The diverse applications of these nanoparticles make them desirable candidate for areas such as drug delivery, coasmetics, medicine, electronics, and contrast agents for magnetic resonance imaging (MRI) and so on. Iron oxide magnetic nanoparticles are a branch of nanoparticles which is specifically being considered as a contrast agent for MRI as well as targeted drug delivery vehicles, angiogenic therapy and chemotherapy as small size gives them advantage to travel intravascular or intracavity actively for drug delivery. Besides the mentioned advantages, the toxicity of the iron oxide magnetic nanoparticles is still less explored. For in vivo applications magnetic nanoparticles should be nontoxic and compatible with the body fluids. These particles tend to degrade in the body hence there is a need to understand the toxicity of the particles as whole and degraded products interacting within the body. Some nanoparticles have demonstrated toxic effects such inflammation, ulceration, and decreases in growth rate, decline in viability and triggering of neurobehavioral alterations in plants and cell lines as well as in animal models. The cause of nanoparticles' toxicity is attributed to their specific characteristics of great surface to volume ratio, chemical composition, size, and dosage, retention in body, immunogenicity, organ specific toxicity, breakdown and elimination from the body. In the current review paper, we aim to sum up the current knowledge on the toxic effects of different magnetic nanoparticles on cell lines, marine organisms and rodents. We believe that the comprehensive data can provide significant study parameters and recent developments in the field. Thereafter, collecting profound knowledge on the background of the subject matter, will contribute to drive research in this field in a new sustainable direction.

Review of Copper and Copper Nanoparticle Toxicity in Fish.

This review summarizes the present knowledge on the toxicity of copper and copper nanoparticles (CuNPs) to various fish species. In previous decades, the excessive usage of metal and metallic nanoparticles has increased significantly, increasing the probability of the accumulation and discharge of metals in various trophic levels of the environment. Due to these concerns, it is important to understand the toxicity mechanisms of metals and metallic nanoparticles before they lead to unhealthy effects on human health. In this review paper, we specifically focus on the effect of metal copper and CuNPs on different fish organs under different physiochemical parameters of various water bodies. Nowadays, different forms of copper have distinctive and specific usages, e.g., copper sulfate is a well-established pesticide which is used to control the growth of algae in lakes and ponds. Deactivating the fungi enzymes prevents fungal spores from germinating. This process of deactivation is achieved via the free cupric ions, which are established as the most toxic forms of copper. Complexes of copper with other ligands may or may not be bioavailable for use in aquatic organisms. On the other hand, CuNPs have shown cost-effectiveness and numerous promising uses, but the toxicity and availability of copper in a nanoparticle form is largely unknown, Additionally, physiochemical factors such as the hardness of the water, alkalinity, presence of inorganic and organic ligands, levels of pH, and temperature in various different water bodies affect the toxicity caused by copper and CuNPs. However, comprehensive knowledge and data regarding the pattern of toxicity for copper metal ions and CuNPs in marine organisms is still limited. In this review, we carry out a critical analysis of the availability of the toxicological profiles of copper metal ions and CuNPs for different fishes in order to understand the toxicity mechanisms of copper and CuNPs. We believe that this review will provide valuable information on the toxicological profile of copper, which will further help in devising safe guidelines for the usage of copper and CuNPs in a sustainable manner.

Surface Modification of Magnetic Nanoparticles by Carbon-Coating Can Increase Its Biosafety: Evidences from Biochemical and Neurobehavioral Tests in Zebrafish.

Recently, magnetic nanoparticles (MNPs) have gained much attention in the field of biomedical engineering for therapeutic as well as diagnostic purposes. Carbon magnetic nanoparticles (C-MNPs) are a class of MNPs categorized as organic nanoparticles. C-MNPs have been under considerable interest in studying in various applications such as magnetic resonance imaging, photothermal therapy, and intracellular transportof drugs. Research work is still largely in progress for testing the efficacy of C-MNPs on the theranostics platform in cellular studies and animal models. In this study, we evaluated the neurobehavioral toxicity parameters on the adult zebrafish (Danio rerio) at either low (1 ppm) or high (10 ppm) concentration level of C-MNPs over a period of two weeks by waterborne exposure. The physical properties of the synthesized C-MNPs were characterized by transmission electron microscopy, Raman, and XRD spectrum characterization. Multiple behavior tests for the novel tank, mirror biting, predator avoidance, conspecific social interaction, shoaling, and analysis of biochemical markers were also conducted to elucidate the corresponding mechanism. Our data demonstrate the waterborne exposure of C-MNPs is less toxic than the uncoated MNPs since neither low nor high concentration C-MNPs elicit toxicity response in behavioral and biochemical tests in adult zebrafish. The approach combining biochemical and neurobehavioral approaches would be helpful for understanding C-MNPs association affecting the bioavailability, biosafety, interaction, and uptake of these C-MNPs in the living organism.

A Novel Function of the Lysophosphatidic Acid Receptor 3 (LPAR3) Gene in Zebrafish on Modulating Anxiety, Circadian Rhythm Locomotor Activity, and Short-Term Memory.

Lysophosphatidic acid (LPA) is a small lysophospholipid molecule that activates multiple cellular functions through pathways with G-protein-coupled receptors. So far, six LPA receptors (LPAR1 to LPAR6) have been discovered and each one of them can connect to the downstream cell message-transmitting network. A previous study demonstrated that LPA receptors found in blood-producing stem cells can enhance erythropoietic processes through the activation of LPAR3. In the current study, newly discovered functions of LPAR3 were identified through extensive behavioral tests in lpar3 knockout (KO) zebrafish. It was found that the adult lpar3 KO zebrafish display an abnormal movement orientation and altered exploratory behavior compared to that of the control group in the three-dimensional locomotor and novel tank tests, respectively. Furthermore, consistent with those results, in the circadian rhythm locomotor activity test, the lpar3 KO zebrafish showed a lower level of angular velocity and average speed during the light cycles, indicating an hyperactivity-like behavior. In addition, the mutant fish also exhibited considerably higher locomotor activity during the dark cycle. Supporting those findings, this phenomenon was also displayed in the lpar3 KO zebrafish larvae. Furthermore, several important behavior alterations were also observed in the adult lpar3 KO fish, including a lower degree of aggression, less interest in conspecific social interaction, and looser shoal formation. However, there was no significant difference regarding the predator avoidance behavior between the mutant and the control fish. In addition, lpar3 KO zebrafish displayed memory deficiency in the passive avoidance test. These in vivo results support for the first time that the lpar3 gene plays a novel role in modulating behaviors of anxiety, aggression, social interaction, circadian rhythm locomotor activity, and memory retention in zebrafish.

Nanoplastics Cause Neurobehavioral Impairments, Reproductive and Oxidative Damages, and Biomarker Responses in Zebrafish: Throwing up Alarms of Wide Spread Health Risk of Exposure.

Plastic pollution is a growing global emergency and it could serve as a geological indicator of the Anthropocene era. Microplastics are potentially more hazardous than macroplastics, as the former can permeate biological membranes. The toxicity of microplastic exposure on humans and aquatic organisms has been documented, but the toxicity and behavioral changes of nanoplastics (NPs) in mammals are scarce. In spite of their small size, nanoplastics have an enormous surface area, which bears the potential to bind even bigger amounts of toxic compounds in comparison to microplastics. Here, we used polystyrene nanoplastics (PS-NPs) (diameter size at ~70 nm) to investigate the neurobehavioral alterations, tissue distribution, accumulation, and specific health risk of nanoplastics in adult zebrafish. The results demonstrated that PS-NPs accumulated in gonads, intestine, liver, and brain with a tissue distribution pattern that was greatly dependent on the size and shape of the NPs particle. Importantly, an analysis of multiple behavior endpoints and different biochemical biomarkers evidenced that PS-NPs exposure induced disturbance of lipid and energy metabolism as well as oxidative stress and tissue accumulation. Pronounced behavior alterations in their locomotion activity, aggressiveness, shoal formation, and predator avoidance behavior were exhibited by the high concentration of the PS-NPs group, along with the dysregulated circadian rhythm locomotion activity after its chronic exposure. Moreover, several important neurotransmitter biomarkers for neurotoxicity investigation were significantly altered after one week of PS-NPs exposure and these significant changes may indicate the potential toxicity from PS-NPs exposure. In addition, after ~1-month incubation, the fluorescence spectroscopy results revealed the accumulation and distribution of PS-NPs across zebrafish tissues, especially in gonads, which would possibly further affect fish reproductive function. Overall, our results provided new evidence for the adverse consequences of PS-NPs-induced behavioral dysregulation and changes at the molecular level that eventually reduce the survival fitness of zebrafish in the ecosystem.

Ecotoxicity Assessment of Fe3O4 Magnetic Nanoparticle Exposure in Adult Zebrafish at an Environmental Pertinent Concentration by Behavioral and Biochemical Testing.

Magnetic Nanoparticles (MNPs) are widely being investigated as novel promising multifunctional agents, specifically in the fields of development for theranostics, electronics, waste water treatment, cosmetics, and energy storage devices. Unique, superior, and indispensable properties of magnetization, heat transfer, and melting temperature make MNPs emerge in the field of therapeutics in future healthcare industries. However, MNPs ecotoxicity as well as behavioral toxicity is still unexplored. Ecotoxicity analysis may assist investigate MNPs uptake mechanism and its influence on bioavailability under a given set of environmental factors, which can be followed to investigate the biomagnification of MNPs in the environment and health risk possessed by them in an ecological food chain. In this study, we attempted to determine the behavioral changes in zebrafishes at low (1 ppm) or high (10 ppm) concentration levels of Fe3O4 MNPs. The synthesized Fe3O4 MNPs sized at 15 nm were characterized by the transmission electron microscope (TEM), the superconducting quantum interference device (SQUID) magnetometer, and the multiple behavior tests for novel tank, mirror biting, conspecific social interaction, shoaling, circadian rhythm, and short-term memory of zebrafish under MNPs chronic exposure were demonstrated. Low concentration MNP exposure did not trigger alteration for majority behavioral and biochemical tests in adult zebrafish. However, tight shoal groups were observed at a high concentration of MNPs exposure along with a modest reduction in fish exploratory behavior and a significant reduction in conspecific social interaction behavior. By using enzyme-linked immunosorbent assays (ELISA), we found a high dose of MNPs exposure significantly elevated cortisol, acetylcholine, and catalase levels while reducing serotonin, acetylcholine esterase, and dopamine levels in the brain. Our data demonstrates chronic MNPs exposure at an environmentally-relevant dose is relatively safe by supporting evidence from an array of behavioral and biochemical tests. This combinational approach using behavioral and biochemical tests would be helpful for understanding the MNPs association with anticipated colloids and particles effecting bioavailability and uptake into cells and organisms.