Size matters: Zebrafish (Danio rerio) as a model to study toxicity of nanoplastics from cells to the whole organism

Polystyrene microplastics exhibit toxic effects on the widespread coral symbiotic Cladocopium goreaui

Within the coral reef habitat, members of the Symbiodiniaceae family stand as pivotal symbionts for reef-building corals. However, the physiological response of Symbiodiniaceae on microplastics are still poorly understood. Research conducted in this investigation assessed the harmful impact of polystyrene microparticles (PS-MPs) on Cladocopium goreaui, a Symbiodiniaceae species with a broad distribution. The results showed that micrometre-sized PS-MPs had a greater toxic effect on C. goreaui than nanometre-sized PS-MPs, and the growth inhibition rate of a concentration of 20 mg/L with 10 μm-sized PS-MPs on C. goreaui was as high as 62.9%-86%, which almost completely inhibited cell proliferation. Exposure to 10 μm PS-MPs significantly increased cell damage, for instance, the concentration of extracellular polymeric substance and malondialdehyde have increased by 161.6%-184.4% and 261.8%-896% on days 10 to 20 respectively. Furthermore, When PS-MPs inhibited the photosynthesis of C. goreaui, it could ensure their typical photosynthetic activity maintained by increasing their chlorophyll levels, and the increase in chlorophyll concentration is proportional to the level of inhibition experienced. However, Exposure to 10 μm PS-MPs could damage the chloroplasts of C. goreaui, leading to a decrease in the ability to synthesize photosynthetic pigments and subsequently resulting in a reduction in photosynthetic capacity. The morphology and genetic activity of C. goreaui suggest that PS-MPs primarily induce cellular shrinkage and distortion, as well as the disintegration and impairment of nuclear and chloroplastic structures, concurrently eliciting a greater number of suppressed genes, predominantly those associated with the function of succinate dehydrogenase, the attachment to tetrapyrroles, the binding of haem, and the handling of iron ions, including activities related to oxidoreduction. The investigation examined the adverse impacts of PS-MPs on a crucial coral symbiont (Symbiodiniaceae) and the beneficial reaction of these algal organisms, enhancing comprehension of how microplastic pollution affects the coral reef ecosystem.

The role of chorion integrity on the bioaccumulation and toxicity of selenium nanoparticles in Japanese medaka (Oryzias latipes)

Selenium nanoparticles (nano-Se) have a wide range of biomedical and agricultural applications. However, there is little information on the potential toxicity of nano-Se once it enters the environment, particularly in fish. The first line of defense from contaminants that embryonic fish have is the chorion, but the degree to which the chorion protects the developing embryo is unknown. Japanese medaka (Oryzias latipes) embryos were exposed to nano-Se in a wide range of concentrations (0.1-400 µM). The importance of chorion integrity was evaluated by exposing embryos to 16 nm nano-Se under four degrees of dechorionation: intact, roughened, partially-dechorionated, fully-dechorionated. Then, effects of particle size on embryos and larvae were determined using four sizes of nano-Se particles (16, 25-50, 50, 100 nm). The results showed that nano-Se exposure reduced survival, development, and hatching. Nano-Se was observed to adsorb on the chorion, with the amount decreasing with increased degree of dechorionation. Toxicity increased with increasing degree of dechorionation, and smaller-sized nano-Se crossed intact chorion more readily and resulted in higher toxicity than larger ones. In larvae, nano-Se accumulated on the skin and was more toxic compared to embryos. This study demonstrated the importance of the chorion in protecting developing embryos and effects of nanoparticle size on its bioavailability and subsequent toxicity.

Microplastics aggravate the adverse effects of methylmercury than inorganic mercury on zebrafish (Danio rerio)

The potential health risks of microplastics (MPs) and their combined exposure with heavy metals such as mercury (Hg) in aquatic environment are increasingly concerned recently. In this work, zebrafish embryos were exposed to different levels of polystyrene microplastics (PS-MPs, ∼0.1 μm) coupled with Hg(II) or/and MeHg at 20 μg/L, to investigate the tissue biodistribution and accumulation of PS-MPs and Hg species, and their interaction, as well as embryo toxicity, oxidative stress and metabolic profiles. With zebrafish embryo development, PS-MPs were ingested and then primarily translocated to yolk sac, liver, and intestinal tissues, further acted as a significant vector for improving the bioaccumulation of MeHg vs. Hg(II). Whatever single or combined exposure of PS-MPs and Hg species, embryo disorders, such as delayed hatching, developmental abnormalities, and motor behavioral, and increased oxidative stress indications were obviously found. Herein, PS-MPs + MeHg aggravated oxidative stress compared with MeHg alone, which might been relevant to the high accumulation of Hg level in zebrafish larvae induced by PS-MPs. Non-targeted metabolomics results proved PS-MPs involvement disturbed lipid metabolism, amino acid metabolism, and energy metabolism compared with alone Hg(II) or MeHg exposure, of which excessive energy metabolism by activating the glycolysis process was found in PS-MPs + MeHg treatment. This work reveals the enhancement efficacy of PS-MPs on MeHg induced toxicity and adverse stress, further proving the differentiated effect of elemental chemical forms with microplastics. In the future, elemental species must be considered for the combined toxicity evaluation and ecological risk assessments of microplastics and heavy metals.

Biotransport and toxic effects of micro- and nanoplastics in fish model and their potential risk to humans: A review

The growing body of scientific evidence suggests that micro- and nanoplastics (MPs/NPs) pose a significant threat to aquatic ecosystems and human health. These particles can enter organisms through ingestion, inhalation, dermal contact, and trophic transfer. Exposure can directly affect multiple organs and systems (respiratory, digestive, neurological, reproductive, urinary, cardiovascular) and activate extensive intracellular signaling, inducing cytotoxicity involving mechanisms such as membrane disruption, extracellular polymer degradation, reactive oxygen species (ROS) production, DNA damage, cellular pore blockage, lysosomal instability, and mitochondrial depolarization. This review focuses on current research examining the in vivo and in vitro toxic effects of MPs/NPs on aquatic organisms, particularly fish, in relation to particulate toxicity aspects (such as particle transport mechanisms and structural modifications). Meanwhile, from the perspectives of the food chain and environmental factors, it emphasizes the comprehensive threats of MPs/NPs to human health in terms of both direct and indirect toxicity. Additionally, future research needs and strategies are discussed to aid in mitigating the potential risks of particulate plastics as carriers of toxic trace elements to human health.

Ecological fitness impairments induced by chronic exposure to polyvinyl chloride nanospheres in Daphnia magna

The aim of this study was to evaluate the effects of chronic exposure (21 days) to an environmentally relevant concentration (10 μg/L) of two different nanoplastic (NP) polymers on the aquatic model organism Daphnia magna. This study examined the impact of exposure to 200 nm polystyrene nanoplastics (PS-NPs) and polyvinyl chloride nanoplastics (PVC-NPs), which had an average size similar to that of PS-NPs (ranging from 50 nm to 350 nm). The effects of polymer exposure on morphometric parameters, number of molts, swimming behaviour, and reproductive outcomes were evaluated. The findings indicate that PVC exposure induced higher body dimensions, while both polymers resulted in an increase in molting behaviour. Moreover, exposure to PVC-NPs had a negative impact on the reproduction of D. magna, as evidenced by a delay in the day of the first brood, a reduction in the total number of offspring produced, and, consequently, a slower population growth rate. It is hypothesised that the ingestion of PVC-NPs by D. magna may have resulted in an impairment of ecdysone hormone functionality and that the increased moulting events potentially representing an adaptive response to the negative effects of PVC-NP adhesion to the organism's body surfaces. These two organisms' responses could concur to explain the observed effects. This study identified the fitness impairments caused by exposure to PVC-NPs, which can lead to relevant ecological consequences. The comparative analysis of the effects induced by two types of polymers has revealed the generation of disparate hazards to D. magna. Furthermore, the chemical composition appears to be a pivotal factor in the onset of these effects. It can therefore be stated that PS is not a suitable standard for representing the toxicity of all plastics.

Meta-analysis of the effects of microplastic on fish: Insights into growth, survival, reproduction, oxidative stress, and gut microbiota diversity

Aquatic ecosystems are primary repositories for microplastics (MPs), which pose significant risks to aquatic organisms. This study addresses the gap in understanding the effects of MPs pollution by analyzing 3,757 biological endpoints from 85 laboratory studies. Overall, our results indicate that MPs exposure significantly inhibits fish growth, survival, and reproductive ability, and increases oxidative damage, specifically, MPs exposure leads to elevated levels of malondialdehyde. However, MPs do not have a significant impact on the diversity of fish gut microbiota. Subgroup and correlation analyses indicate that the extent of various toxic effects is influenced by multiple factors, including MPs' type, exposure pathway, size, concentration, as well as the aquatic environment or life stage of the fish. In addition, the regression analysis revealed a relationship between the magnitude of toxic effects and the size, concentration, or duration of MPs exposure. This study provides useful information for understanding the potential impacts of MPs on aquatic organisms and offers new insights for the protection and management of aquatic ecosystems.

Trophic transfer and bioaccumulation of nanoplastics in Coryphaena hippurus (mahi-mahi) and effect of depuration

Ocean plastic pollution is a global concern, exacerbated by the distinctive physiochemical characteristics of nanoplastics (NPs), making it crucial to study the impacts on marine animals, particularly fish, given their ecological and economic importance. Both trophic transfer and waterborne exposure are potential modes of NP entry into seafood for human consumption Although the majority of studies have focused on in-vitro impacts of NP exposure in fish, in-vivo methods can offer a more holistic understanding of these impacts. This study investigates polystyrene NP transfer to Coryphaena hippurus (mahi-mahi) larvae, a widely consumed fish and significant marine predator, during the early life stage. Brachionus plicatilis (rotifers) were exposed to NPs, and subsequently fed to C. hippurus larvae, with exposure duration ranging from 24 to 96 h. Significant NP transfer was observed via the food chain, varying with exposure duration. A depuration study over 72 h, simulating intermittent NP exposure, revealed substantial NP excretion but also notable retention in the larvae. Biodistribution analysis indicated that most NPs accumulated in the gut, with a significant portion remaining post-depuration and some translocating to other body areas containing vital organs like the heart, liver, and gall bladder. Despite no significant effects on body length and eye diameter during this short study period, histopathological analysis revealed intestinal tissue damage in the larvae. Overall, this study provides valuable insight into the trophic transfer of NPs in marine food webs, emphasizing the need for further research on ecological impacts and highlighting the importance of addressing NP contamination to protect marine ecosystems and food safety.

Rapid Generation of Microplastics and Plastic-Derived Dissolved Organic Matter from Food Packaging Films under Simulated Aging Conditions

In this study, we show that low-density polyethylene films, a prevalent choice for food packaging in everyday life, generated high numbers of microplastics (MPs) and hundreds to thousands of plastic-derived dissolved organic matter (DOM) substances under simulated food preparation and storage conditions. Specifically, the plastic film generated 66-2034 MPs/cm2 (size range 10-5000 μm) under simulated aging conditions involving microwave irradiation, heating, steaming, UV irradiation, refrigeration, freezing, and freeze-thaw cycling alongside contact with water, which were 15-453 times that of the control (plastic film immersed in water without aging). We also noticed a substantial release of plastic-derived DOM. Using ultrahigh-resolution mass spectrometry, we identified 321-1414 analytes with molecular weights ranging from 200 to 800 Da, representing plastic-derived DOM containing C, H, and O. The DOM substances included both degradation products of polyethylene (including oxidized forms of oligomers) and toxic plastic additives. Interestingly, although no apparent oxidation was observed for the plastic film under aging conditions, plastic-derived DOM was more oxidized (average O/C increased by 27-46%) following aging with a higher state of carbon saturation and higher polarity. These findings highlight the future need to assess risks associated with MP and DOM release from plastic wraps.

Genotoxic and neurotoxic potential of intracellular nanoplastics: A review

Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.

Toxic effects of microplastic and nanoplastic on the reproduction of teleost fish in aquatic environments

Microplastics and nanoplastics are widely present in aquatic environments and attract significant scholarly attention due to their toxicity, persistence, and ability to cross biological barriers, which pose substantial risks to various fish species. Microplastics and nanoplastics can enter fish through their digestive tract, gills and skin, causing oxidative damage to the body and adversely affecting their reproductive system. Given that fish constitute a crucial source of high-quality protein for humans, it is necessary to study the impact of microplastics on fish reproduction in order to assess the impact of pollutants on ecology, biodiversity conservation, environmental sustainability, and endocrine disruption. This review explores the reproductive consequences of microplastics and nanoplastics in fish, examining aspects such as fecundity, abnormal offspring, circadian rhythm, gonad index, spermatocyte development, oocyte development, sperm quality, ovarian development, and changes at the molecular and cellular level. These investigations hold significant importance in environmental toxicology.

Assessing the abundance, sources, and potential ecological risk assessment of microplastics using their particle and mass units in Uiam Lake, South Korea

Microplastics (MPs) enter lakes through various pathways, including effluents from wastewater treatment plants (WWTPs), surface runoff, and improperly disposed of plastic waste. In this study, the extent of MPs pollution in Uiam Lake in fall of 2022 and spring of 2023 was assessed by determining both the number (n/m3) and mass concentrations (μg/m3) of MPs. Moreover, the correlation between water quality parameters and MP properties was analyzed, and an ecological risk assessment was conducted. MPs abundance was higher in spring than in fall, probably due to the lifting of coronavirus disease-19 restrictions, melting of ice, higher rainfall, and faster wind speed. Fragment was the dominant shape of the MPs collected, while polyvinyl chloride (PVC) and polyester/polyethylene terephthalate were the frequently detected polymer types of MPs in fall and spring, respectively. There was a moderate positive correlation between the number concentration of MPs and the total nitrogen, total phosphorus (T-P), and total organic carbon levels; in contrast, there was no significant relationship between the mass concentration of MPs and all water quality parameters. However, the abundance (μg/m3) of PVC and polymethyl methacrylate MPs were positively correlated with T-P and electrical conductivity. The pollution load index, polymer hazard index, and potential ecological risk index (PERI) were generally higher when the mass unit of MPs was used due to the presence of large-sized MPs composed of highly hazardous polymers (e.g., polyurethane, PVC, and alkyd). For instance, the PERI value of the WWTP effluent was at the very high level (>1200) in both seasons, regardless of the abundance unit of MPs. Therefore, WWTP effluents may have increased the ecological toxicity of MPs pollution in Uiam Lake.

Polystyrene nanoparticles with different particle sizes cause autophagy by ROS/ERS/FOXO1 axis in the Cyprinus carpio kidney affecting immunological function

Microplastic pollution poses challenges for ecosystems worldwide, and nanoplastics (NPs, 1-1000 nm) have been identified as persistent pollutants. However, although some studies have described the hazards of NPs to aquatic organisms, the toxicological processes of NPs in the common carp kidney and the biotoxicity of differently sized NPs remain unclear. In this study, we used juvenile common carp as an in vivo model that were constantly exposed to freshwater at 1000 μg/L polystyrene nanoparticle (PSNP) concentrations (50, 100, and 400 nm) for 28 days. Simultaneously, we constructed an in vitro model utilizing grass fish kidney cells (CIK) to study the toxicological effects of PSNPs of various sizes. We performed RT-PCR and Western blot assays on the genes involved in FOXO1, HMGB1, HIF-1α, endoplasmic reticulum stress, autophagy, and immunoreaction. According to these results, exposure to PSNPs increased reactive oxygen species (ROS) levels, and the carp kidneys experienced endoplasmic reticulum stress. Additionally, PSNPs promoted renal autophagy by activating the ROS/ERS/FOXO1 (ERS: endoplasmic reticulum stress) pathway, and it affected immunological function by stimulating the ROS/HMGB1/HIF-1α signaling pathway. This study provides new insights into the contamination hazards of NPs in freshwater environments, as well as the harm they pose to the human living environments. The relationship between particle size and the degree of damage caused by PSNPs to organisms is a potential future research direction.

Natural compounds-based nanomedicines for cancer treatment: Future directions and challenges

Several efforts have been extensively accomplished for the amelioration of the cancer treatments using different types of new drugs and less invasives therapies in comparison with the traditional therapeutic modalities, which are widely associated with numerous drawbacks, such as drug resistance, non-selectivity and high costs, restraining their clinical response. The application of natural compounds for the prevention and treatment of different cancer cells has attracted significant attention from the pharmaceuticals and scientific communities over the past decades. Although the use of nanotechnology in cancer therapy is still in the preliminary stages, the application of nanotherapeutics has demonstrated to decrease the various limitations related to the use of natural compounds, such as physical/chemical instability, poor aqueous solubility, and low bioavailability. Despite the nanotechnology has emerged as a promise to improve the bioavailability of the natural compounds, there are still limited clinical trials performed for their application with various challenges required for the pre-clinical and clinical trials, such as production at an industrial level, assurance of nanotherapeutics long-term stability, physiological barriers and safety and regulatory issues. This review highlights the most recent advances in the nanocarriers for natural compounds secreted from plants, bacteria, fungi, and marine organisms, as well as their role on cell signaling pathways for anticancer treatments. Additionally, the clinical status and the main challenges regarding the natural compounds loaded in nanocarriers for clinical applications were also discussed.

Evaluation of the Effectiveness of Eugenol and MS-222 as Anesthetics in Zebrafish in Repeated Exposures and Post-Anesthesia Behaviour

The increasing use of the zebrafish (Danio rerio) in scientific experiments has made it necessary to implement anesthesia protocols guaranteeing minimum pain and suffering for these animals and ensuring the reliability of the results obtained from their research. Therefore, we aimed to compare the effectiveness of two anesthetics, eugenol and MS-222, in consecutive administrations and evaluate the zebrafish behaviour after repeated anesthesia. Thus, several zebrafish were anaesthetized with eugenol, MS-222, and buffered MS-222 three times repeatedly with a 24-h interval between each exposure. The induction and recovery periods were also timed. Their swimming frequency was determined after each exposure to assess their behaviour after the anesthesia. Anesthesia induction was quicker with eugenol compared to MS-222. However, eugenol presented longer recovery times, which were prolonged after each exposure. Also, the swimming frequency was reduced after each anesthesia with eugenol. The buffered version of MS-222 was more efficacious than the non-buffered one. Both versions of MS-222 did not affect the swimming frequency. Based on these findings, we recommend the utilization of MS-222 buffered rather than eugenol when repeated, brief-duration anesthesia is necessitated for a study.

Polystyrene nanoplastics as an ecotoxicological hazard: cellular and transcriptomic evidences on marine and freshwater in vitro teleost models

The contamination of marine and freshwater environments by nanoplastics is considered a global threat for aquatic biota. Taking into account the most recent concentration range estimates reported globally and recognizing a knowledge gap in polystyrene nanoplastics (PS-NPs) ecotoxicology, the present work investigated the harmful effects of 20 nm and 80 nm PS-NPs, at increasing biological complexity, on the rainbow trout Oncorhynchus mykiss RTG-2 and gilthead seabream Sparus aurata SAF-1 cell lines. Twenty nm PS-NPs exerted a greater cytotoxicity than 80 nm ones and SAF-1 were approximately 4-fold more vulnerable to PS-NPs than RTG-2. The engagement of PS-NPs with plasma membranes was accompanied by discernible uptake patterns and morphological alterations along with a nuclear translocation already within a 30-min exposure. Cells were structurally damaged only by the 20 nm PS-NPs in a time-dependent manner as indicated by distinctive features of the execution phase of the apoptotic cell death mechanism such as cell shrinkage, plasma membrane blebbing, translocation of phosphatidylserine to the outer leaflet of the cell membrane and DNA fragmentation. At last, functional analyses unveiled marked transcriptional impairment at both sublethal and lethal doses of 20 nm PS-NPs, with the latter impacting the "Steroid biosynthesis", "TGF-beta signaling pathway", "ECM-receptor interaction", "Focal adhesion", "Regulation of actin cytoskeleton" and "Protein processing in endoplasmic reticulum" pathways. Overall, a distinct ecotoxicological hazard of PS-NPs at environmentally relevant concentrations was thoroughly characterized on two piscine cell lines. The effects were demonstrated to depend on size, exposure time and model, emphasizing the need for a comparative evaluation of endpoints between freshwater and marine ecosystems.

From tissue lesions to neurotoxicity: The devastating effects of small-sized nanoplastics on red drum Sciaenops ocellatus

Nanoplastic pollution typically exhibits more biotoxicity to marine organisms than microplastic pollution. Limited research exists on the toxic effects of small-sized nanoplastics on marine fish, especially regarding their post-exposure resilience. In this study, red drum (Sciaenops ocellatus) were exposed to small-sized polystyrene nanoplastics (30 nm, PS-NPs) for 7 days for the exposure experiments, followed by 14 days of recovery experiments. Histologically, hepatic lipid droplets and branchial epithelial liftings were the primary lesions induced by PS-NPs during both exposure and recovery periods. The inhibition of total superoxide dismutase activity and the accumulation of malondialdehyde content throughout the exposure and recovery periods. Transcriptional and metabolic regulation revealed that PS-NPs induced lipid metabolism disorders and DNA damage during the initial 1-2 days of exposure periods, followed by immune responses and neurotoxicity in the later stages (4-7 days). During the early recovery stages (2-7 days), lipid metabolism and cell cycle were activated, while in the later recovery stage (14 days), the emphasis shifted to lipid metabolism and energy metabolism. Persistent histological lesions, changes in antioxidant capacity, and fluctuations in gene and metabolite expression were observed even after 14 days of recovery periods, highlighting the severe biotoxicity of small-sized PS-NPs to marine fish. In summary, small-sized PS-NPs have severe biotoxicity, causing tissue lesions, oxidative damage, lipid metabolism disorders, DNA damage, immune responses, and neurotoxicity in red drum. This study offers valuable insights into the toxic effects and resilience of small-sized nanoplastics on marine fish.

Decoding the molecular concerto: Toxicotranscriptomic evaluation of microplastic and nanoplastic impacts on aquatic organisms

The pervasive and steadily increasing presence of microplastics/nanoplastics (MPs/NPs) in aquatic environments has raised significant concerns regarding their potential adverse effects on aquatic organisms and their integration into trophic dynamics. This emerging issue has garnered the attention of (eco)toxicologists, promoting the utilization of toxicotranscriptomics to unravel the responses of aquatic organisms not only to MPs/NPs but also to a wide spectrum of environmental pollutants. This review aims to systematically explore the broad repertoire of predicted molecular responses by aquatic organisms, providing valuable intuitions into complex interactions between plastic pollutants and aquatic biota. By synthesizing the latest literature, present analysis sheds light on transcriptomic signatures like gene expression, interconnected pathways and overall molecular mechanisms influenced by various plasticizers. Harmful effects of these contaminants on key genes/protein transcripts associated with crucial pathways lead to abnormal immune response, metabolic response, neural response, apoptosis and DNA damage, growth, development, reproductive abnormalities, detoxification, and oxidative stress in aquatic organisms. However, unique challenge lies in enhancing the fingerprint of MPs/NPs, presenting complicated enigma that requires decoding their specific impact at molecular levels. The exploration endeavors, not only to consolidate existing knowledge, but also to identify critical gaps in understanding, push forward the frontiers of knowledge about transcriptomic signatures of plastic contaminants. Moreover, this appraisal emphasizes the imperative to monitor and mitigate the contamination of commercially important aquatic species by MPs/NPs, highlighting the pivotal role that regulatory frameworks must play in protecting all aquatic ecosystems. This commitment aligns with the broader goal of ensuring the sustainability of aquatic resources and the resilience of ecosystems facing the growing threat of plastic pollutants.

Selective bioaccumulation of polystyrene nanoplastics in fetal rat brain and damage to myelin development

Micro(nano)plastic, as a new type of environmental pollutant, have become a potential threat to the life and health of various stages of biology. However, it is not yet clear whether they will affect brain development in the fetal stage. Therefore, this study aims to explore the potential effects of nanoplastics on the development of fetal rat brains. To assess the allocation of NPs (25 nm and 50 nm) in various regions of the fetal brain, pregnant rats were exposed to concentrations (50, 10, 2.5, and 0.5 mg/kg) of PS-NPs. Our results provided evidence of the transplacental transfer of PS-NPs to the fetal brain, with a prominent presence observed in several cerebral regions, notably the cerebellum, hippocampus, striatum, and prefrontal cortex. This distribution bias might be linked to the developmental sequence of each brain region. Additionally, we explored the influence of prenatal exposure on the myelin development of the cerebellum, given its the highest PS-NP accumulation in offspring. Compared with control rats, PS-NPs exposure caused a significant reduction in myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) expression, a decrease in myelin thickness, an increase in cell apoptosis, and a decline in the oligodendrocyte population. These effects gave rise to motor deficits. In conclusion, our results identified the specific distribution of NPs in the fetal brain following prenatal exposure and revealed that prenatal exposure to PS-NPs can suppress myelin formation in the cerebellum of the fetus.

Investigation of the effects of nanoplastic polyethylene terephthalate on environmental toxicology using model Drosophila melanogaster

Plastic pollution has become a major environmental concern, and various plastic polymers are used daily. A study was conducted to examine the toxic effects of polyethylene terephthalate (PET) nanoplastics (NPLs) on Drosophila melanogaster. We have successfully synthesized PET NPLs and characterized using DLS, Zeta potential, TEM, HRTEM, SAED, XRD, FTIR, and Raman spectroscopy to gain crucial insights into the structure and properties. We fed PET NPLs to Drosophila to assess toxicity. ROS was quantified using DCFH-DA and NBT, and the nuclear degradation was checked by DAPI staining. Quantification of protein and activity of antioxidant enzymes like SOD, catalase depicted the adverse consequences of PET NPLs exposure. The dorsal side of the abdomens, eyes, and wings were also defective when phenotypically analyzed. These results substantiate the genotoxic and cytotoxic impact of nanoplastics. Notably, behavioral observations encompassing larval crawling and climbing of adults exhibit normal patterns, excluding the presence of neurotoxicity. Adult Drosophila showed decreased survivability, and fat accumulation enhanced body weight. These findings contribute to unraveling the intricate mechanisms underlying nanoplastic toxicity and emphasize its potential repercussions for organismal health and ecological equilibrium.

Nanoplastic contamination: Impact on zebrafish liver metabolism and implications for aquatic environmental health

Nanoplastics (NPs) are increasingly pervasive in the environment, raising concerns about their potential health implications, particularly within aquatic ecosystems. This study investigated the impact of polystyrene nanoparticles (PSN) on zebrafish liver metabolism using liquid chromatography hybrid quadrupole time of flight mass spectrometry (LC-QTOF-MS) based non-targeted metabolomics. Zebrafish were exposed to 50 nm PSN for 28 days at low (L-PSN) and high (H-PSN) concentrations (0.1 and 10 mg/L, respectively) via water. The results revealed significant alterations in key metabolic pathways in low and high exposure groups. The liver metabolites showed different metabolic responses with L-PSN and H-PSN. A total of 2078 metabolite features were identified from the raw data obtained in both positive and negative ion modes, with 190 metabolites deemed statistically significant in both L-PSN and H-PSN groups. Disruptions in lipid metabolism, inflammation, oxidative stress, DNA damage, and amino acid synthesis were identified. Notably, L-PSN exposure induced changes in DNA building blocks, membrane-associated biomarkers, and immune-related metabolites, while H-PSN exposure was associated with oxidative stress, altered antioxidant metabolites, and liver injury. For the first time, L-PSN was found depolymerized in the liver by cytochrome P450 enzymes. Utilizing an analytical approach to the adverse outcome pathway (AOP), impaired lipid metabolism and oxidative stress have been identified as potentially conserved key events (KEs) associated with PSN exposure. These KEs further induced liver inflammation, steatosis, and fibrosis at the tissue and organ level. Ultimately, this could significantly impact biological health. The study highlights the PSN-induced effects on zebrafish liver metabolism, emphasizing the need for a better understanding of the risks associated with NPs contamination in aquatic ecosystems.

Nanoplastic Exposure Mediates Neurodevelopmental Toxicity by Activating the Oxidative Stress Response in Zebrafish (Danio rerio)

The global accumulation and adverse effects of nanoplastics (NPs) are a growing concern for the environment and human health. In recent years, more and more studies have begun to focus on the toxicity of plastic particles for early animal development. Different particle sizes of plastic particles have different toxicities to biological development. Nevertheless, the potential toxicological effects of 20 nm NPs, especially on neurodevelopment, have not been well investigated. In this paper, we used fluorescence microscopy to determine neurotoxicity in zebrafish at different concentrations of NPs. Moreover, the behavioral analysis demonstrated that NPs induced abnormal behavior of zebrafish. The results revealed developmental defects in zebrafish embryos after exposure to different concentrations (0, 0.3, 3, and 9 mg/L) of NPs. The morphological deformities, including abnormal body length and the rates of heart, survival, and hatching, were induced after NP exposure in zebrafish embryos. In addition, the development of primary motor neurons was observed the inhibitory effects of NPs on the length, occurrence, and development of primary motor neurons in Tg(hb9:GFP). Quantitative polymerase chain reaction analysis suggested that exposure to NPs significantly affects the expression of the genes involved in the occurrence and differentiation of primary motor neurons in zebrafish. Furthermore, the indicators associated with oxidative stress and apoptosis were found to be modified in zebrafish embryos at 24 and 48 h following exposure to NPs. Our findings demonstrated that NPs could cause toxicity in primary motor neurons by activating the oxidative stress response and inducing apoptosis, consequently impairing motor performance.

Toxic effects of nanoplastics and microcystin-LR coexposure on the liver-gut axis of Hypophthalmichthys molitrix

Plastic products and nutrients are widely used in aquaculture facilities, resulting in copresence of nanoplastics (NPs) released from plastics and microcystins (MCs) from toxic cyanobacteria. The potential effects of NPs-MCs coexposure on aquatic products require investigation. This study investigated the toxic effects of polystyrene (PS) NPs and MC-LR on the gut-liver axis of silver carp Hypophthalmichthys molitrix, a representative commercial fish, and explored the effects of the coexposure on intestinal microorganism structure and liver metabolic function using traditional toxicology and multi-omics association analysis. The results showed that the PS-NPs and MC-LR coexposure significantly shortened villi length, and the higher the concentration of PS-NPs, the more obvious the villi shortening. The coexposure of high concentrations of PS-NPs and MC-LR increased the hepatocyte space in fish, and caused obvious loss of gill filaments. The diversity and richness of the fish gut microbes significantly increased after the PS-NPs exposure, and this trend was amplified in the copresence of MC-LR. In the coexposure, MC-LR contributed more to the alteration of fish liver metabolism, which affected the enrichment pathway in glycerophospholipid metabolism and folic acid biosynthesis, and there was a correlation between the differential glycerophospholipid metabolites and affected bacteria. These results suggested that the toxic mechanism of PS-NPs and MC-LR coexposure may be pathological changes of the liver, gut, and gill tissues, intestinal microbiota disturbance, and glycerophospholipid metabolism imbalance. The findings not only improve the understanding of environmental risks of NPs combined with other pollutants, but also provide potential microbiota and glycerophospholipid biomarkers in silver carp.

Implications of exposure route for the bioaccumulation potential of nanopolystyrene particles

Microplastics and nanoplastics are found in marine biota across a wide range of trophic levels and environments. While a large portion of the information about plastic exposure comes from gastrointestinal (GI) data, the relevance of particle accumulation from an oral exposure compared with other types of exposure (e.g. dermal, respiratory) is unknown. To address this gap in knowledge, larval zebrafish (7 days post fertilization) were exposed to two different sizes of nanoplastics through either oral gavage or a waterborne exposure. Larvae were tracked for 48 h post exposure (hpe) to assess the migration and elimination of plastics. Larvae eliminated orally gavaged nanoplastics within 48 hpe. Oral gavage showed limited particle movement from the GI tract into other tissues. In contrast, waterborne nanoplastic-exposed larvae displayed notable fluorescence in tissues outside of the GI tract. The 50 nm waterborne-exposed larvae retained the particles past 48 hpe, and showed accumulation with neuromasts. For both sizes of plastic particles, the nanoplastics were eliminated from non-GI tract tissues by 24 hpe. Our results suggest that waterborne exposure leads to greater accumulation of plastic in comparison to oral exposure, suggesting that plastic accumulation in certain tissues is greater via routes of exposure other than oral consumption.

Sublethal effects induced by different plastic nano-sized particles in Daphnia magna at environmentally relevant concentrations

A growing number of studies have reported the toxic effects of nanoplastics (NPs) on organisms. However, the focus of these studies has almost exclusively been on the use of polystyrene (PS) nanospheres. Herein, we aim to evaluate the sublethal effects on Daphnia magna juveniles of three different NP polymers: PS-NPs with an average size of 200 nm, polyethylene [PE] NPs and polyvinyl chloride [PVC] NPs with a size distribution between 50 and 350 nm and a comparable mean size. For each polymer, five environmentally relevant concentrations were tested (from 2.5 to 250 μg/L) for an exposure time of 48 h. NP effects were assessed at the biochemical level by investigating the amount of reactive oxygen species (ROS) and the activity of the antioxidant enzyme catalase (CAT) and at the behavioral level by evaluating the swimming behavior (distance moved). Our results highlight that exposure to PVC-NPs can have sublethal effects on Daphnia magna at the biochemical and behavioral levels. The potential role of particle size on the measured effects cannot be excluded as PVC and PE showed a wider size range distribution than PS, with particles displaying sizes from 50 to 350 nm. However, we infer that the chemical structure of PVC, which differs from that of PE of the same range size, concurs to explain the observed effects. Consequently, as PS seems not to be the most hazardous polymer, we suggest that the use of data on PS toxicity alone can lead to an underestimation of NP hazards.

Mechanistic Insights into Cellular and Molecular Basis of Protein-Nanoplastic Interactions

Plastic waste is ubiquitously present across the world, and its nano/sub-micron analogues (plastic nanoparticles, PNPs), raise severe environmental concerns affecting organisms' health. Considering the direct and indirect toxic implications of PNPs, their biological impacts are actively being studied; lately, with special emphasis on cellular and molecular mechanistic intricacies. Combinatorial OMICS studies identified proteins as major regulators of PNP mediated cellular toxicity via activation of oxidative enzymes and generation of ROS. Alteration of protein function by PNPs results in DNA damage, organellar dysfunction, and autophagy, thus resulting in inflammation/cell death. The molecular mechanistic basis of these cellular toxic endeavors is fine-tuned at the level of structural alterations in proteins of physiological relevance. Detailed biophysical studies on such protein-PNP interactions evidenced prominent modifications in their structural architecture and conformational energy landscape. Another essential aspect of the protein-PNP interactions includes bioenzymatic plastic degradation perspective, as the interactive units of plastics are essentially nano-sized. Combining all these attributes of protein-PNP interactions, the current review comprehensively documented the contemporary understanding of the concerned interactions in the light of cellular, molecular, kinetic/thermodynamic details. Additionally, the applicatory, economical facet of these interactions, PNP biogeochemical cycle and enzymatic advances pertaining to plastic degradation has also been discussed.

Nano-plastics and gastric health: Decoding the cytotoxic mechanisms of polystyrene nano-plastics size

Gastrointestinal diseases exert a profound impact on global health, leading to millions of healthcare interventions and a significant number of fatalities annually. This, coupled with escalating healthcare expenditures, underscores the need for identifying and addressing potential exacerbating factors. One emerging concern is the pervasive presence of microplastics and nano-plastics in the environment, largely attributed to the indiscriminate usage of disposable plastic items. These nano-plastics, having infiltrated our food chain, pose a potential threat to gastrointestinal health. To understand this better, we co-cultured human gastric fibroblasts (HGF) with polystyrene nano-plastics (PS-NPs) of diverse sizes (80, 500, 650 nm) and meticulously investigated their cellular responses over a 24-hour period. Our findings revealed PS particles were ingested by the cells, with a notable increase in ingestion as the particle size decreased. The cellular death induced by these PS particles, encompassing both apoptosis and necrosis, showcased a clear dependence on both the particle size and its concentration. Notably, the larger PS particles manifested more potent cytotoxic effects. Further analysis indicated a concerning reduction in cellular membrane potential, alongside a marked increase in ROS levels upon PS particles exposure. This suggests a significant disruption of mitochondrial function and heightened oxidative stress. The larger PS particles were especially detrimental in causing mitochondrial dysfunction. In-depth exploration into the PS particles impact on genes linked with the permeability transition pore (PTP) elucidated that these PS particles instigated an internal calcium rush. This surge led to a compromise in the mitochondrial membrane potential, which in tandem with raised ROS levels, further catalyzed DNA damage and initiated cell death pathways. In essence, this study unveils the intricate mechanisms underpinning cell death caused by PS particles in gastric epithelial cells and highlighting the implications of PS particles on gastrointestinal health. The revelations from this research bear significant potential to shape future healthcare strategies and inform pertinent environmental policies.

Microplastics distribution in river side bars: The combined effects of water level and wind intensity

Rivers are the main pathway for microplastics (MP) transport toward the ocean. However, the understanding of the processes involved in the deposition and mobilization of MP in rivers, specifically in sediment side bars (SB), remains very limited. The objectives of this study were: (i) to examine the effect of hydrometric fluctuations and wind intensity on the distribution of microplastics (MP < 5 mm) in the SB of large river (the Paraná River), (ii) to determine the characteristics of MP to infer their origin and fate, and (iii) to discuss potential similarities or differences between MP suspended in the water column and MP found in sediment. The SB and water column were sampled during the autumn, winter, and spring of 2018, and the summer of 2019 at different river discharges and wind intensities. >90 % of the MP items found were fiber of polyethylene terephthalate (PET; FT-IR analysis), the most common MP color was blue, and most were in the 0.5-2 mm size range. The concentration/composition of MP varied according to the river discharge and wind intensity. During the falling limb of the hydrograph when discharge is decreasing and sediments are exposed for short periods (13-30 days), MP particles transported by the flow were deposited on temporarily exposed SB, accumulating there in high densities (309-373 items/kg). However, during the drought, when sediments remained exposed for a long time (259 days), MP were mobilized and transported by the wind. During this period (no influence of the flow), MP densities significantly decreased on SB (39-47 items/kg). In conclusion, both hydrological fluctuations and wind intensity played a significant role in MP distribution in SB.

The impact of microplastics on female reproduction and early life

Plastic pollution in our environment is one of the most important global health concerns right now. Micro- and nanoplastics (MNPs) are taken up by both humans and animals, mainly via food and water, and can pass important epithelial barriers. Indications of plastics in the blood circulation have recently been shown in both humans and farm animals, but standardized methods to quantify the exact levels of MNPs to which we are exposed are currently lacking. Potential hazards of MNPs are being investigated very recently, including the impact that MNPs may have on reproduction. However, studies on mammalian reproduction are scarce, but a wealth of data from aquatic species indicates reproductive effects of MNPs. The first studies in rodent models demonstrate that MNPs reach the gonads after oral exposure and may impact offspring after maternal exposure during the gestational period. These effects may arise from the particles themselves or the presence of plastic contaminants that leach from plastics. Plastic contamination has been detected in human placentas, fetal fluid and the meconium of newborns, indicating the presence of plastics from the very first start of life. Currently there is a lack of studies that investigate the impact of MNP exposure during the periconception and embryonic period, whereas this is an extremely sensitive period that needs considerable attention with the growing amount of plastics in our environment.

Micro- and nanoplastic toxicity: A review on size, type, source, and test-organism implications

Polymeric wastes are among the current major environmental problems due to potential pollution and contamination. Within the spectrum of polymeric waste, microplastics (MPs) and nanoplastics (NPs) have gained ground in recent research since these particles can affect the local biota, inducing toxic effects on several organisms. Different outcomes have been reported depending on particle sizes, shape, types, and exposed organisms and conditions, among other variables. This review aimed to compile and discuss the current knowledge and possible literature gaps regarding the MPs and NPs generation and their toxicological effects as stressors, considering polymer type (as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyvinyl chloride, or others), size (micro- or nano-scale), source (commercial, lab-synthesized, or environmental) and test organism group. In that sense, 615 publications were analyzed, among which 72 % discussed micro-sized plastics, while <28 % assayed the toxicity of NPs (<1 μm). For most polymers, MPs and NPs were commercially purchased and used without additional size reduction processes; except for polyethylene terephthalate studies that mostly used grinding and cutting methods to obtain MPs. Polystyrene (PS) was the main polymer studied, as both MPs and NPs. PS accounts for >90 % of NPs reports evaluated, reflecting a major literature gap if compared to its 35.3 % share on MPs studies. Among the main organisms, arthropods and fish combined accounted for nearly 40 % of toxicity testing. Overall, the different types of plastics showed a tendency to report toxic effects, except for the 'Survival/lethality' category, which might indicate that polymeric particles induce mostly sublethal toxic effects. Furthermore, despite differences in publication numbers, we observed greater toxicity reported for NPs than MPs with oxidative stress among the majorly investigated endpoints. This study allowed a hazard profile overview of micro/nanoplastics (MNPs) and the visualization of literature gaps, under a broad diversity of toxicological evidence.

Effects of size and surface charge on the sedimentation of nanoplastics in freshwater

The environmental issues caused by nanoplastics (NPs) are increasingly noticeable. Environmental behavior study of the NPs could provide vital information for their environmental impact assessment. However, associations between NPs' inherent properties and their sedimentation behaviors were seldom investigated. In this study, six types of PSNPs (polystyrene nanoplastics) with different charges (positive and negative) and particle sizes (20-50 nm, 150-190 nm and 220-250 nm) were synthesized, and their sedimentations under different environmental factors, (e.g., pH value, ionic strength (IS), electrolyte type and natural organic matter) were investigated. Results displayed that both particle size and surface charge would affect the sedimentation of PSNPs. The maximum sedimentation ratio of 26.48% was obtained in positive charged PSNPs with size of 20-50 nm, while the minimum sedimentation ratio of 1.02% was obtained in negative charged PSNPs with size of 220-250 nm at pH 7.6. The pH value shift (range of 5-10) triggered negligible changes of sedimentation ratio, the average particle size and the Zeta potential. Small size PSNPs (20-50 nm) showed higher sensitivity to IS, electrolyte type and HA condition than large size PSNPs. At high IS value ( [Formula: see text]  = 30 mM or IS_NaCl = 100 mM), the sedimentation ratios of the PSNPs all increased differently according to their properties, and the sedimentation promoting effect of CaCl₂ was more significant on negative charged PSNPs than positive charged PSNPs. When [Formula: see text] increased from 0.9 to 9 mM, the sedimentation ratios of negative charged PSNPs increased by 0.53%-23.49%, while that of positive charged PSNPs increased by less than 10%. Besides, humic acid (HA) addition (1-10 mg/L) would lead to a stable suspension status for PSNPs in water with different degree and perhaps different mechanism due to their charge characteristics. These results showed new light on influence factor studies of NPs' sedimentation and would be helpful for further knowledge of NPs' environmental behaviors.

Comparative toxicity of micro and nanopolystyrene particles in Mya arenaria clams

The contamination of coastal marine environments by plastics of sizes ranging from mm down to the nanoscale (nm) could pose a threat to aquatic organisms. The purpose of this study was to examine the toxicity of polystyrene nanoparticles (PsNP) of various sizes (50, 100 and 1000 nm) to the marine clams Mya arenaria. Clams were exposed to concentrations of PsPP for 7 days at 15 °C and analyzed for uptake/transformation, changes in energy metabolism, oxidative stress, genotoxicity and circadian neural activity. The results revealed that PsNP accumulated in the digestive gland was 50 nm > 100 nm > 1000 nm. All sized increased oxidative stress as follows: 50 nm (peroxidase, antioxidant potential and LPO), 100 nm (LPO and antioxidant potential) and 1000 nm (LPO). Tissue damage was also size dependent by increasing genotoxicity. The 100 nm PsPP altered the levels of the circadian metabolite melatonin. We conclude that the toxicity of plastics is size dependent in clams.

Neurotoxicity of polystyrene nanoplastics with different particle sizes at environment-related concentrations on early zebrafish embryos

Nanoplastics (NPs) have received global attention due to their wide application and detection in various environmental or biological media. NPs can penetrate physical barriers and accumulate in organisms after being ingested, producing a variety of toxic effects and possessing particle size-dependent effects, distinguishing them from traditional contaminants. This paper explored the neurotoxicity of polystyrene (PS)-NPs of different particle sizes on zebrafish (Danio rerio) embryos at environmental concentrations at the tissue and molecular levels using visualized transgenic zebrafish. Results showed that all particle sizes of PS-NPs produced developmental toxicity in zebrafish embryos and induced neuronal loss, axonal deletion/shortening/hybridization, and developmental and apoptotic-related genetic alterations, ultimately leading to behavioral abnormalities. PS-NPs with smaller sizes may have more severe neurotoxicity due to their entry into the embryo and brain through the chorionic pore before hatching. In addition, PS-NPs at 100 nm and 1000 nm can specifically interfere with GABAergic, cholinergic or serotonergic system and affect neuronal signaling. Our results reveal the neurotoxic risk of NPs, and smaller particle-size NPs may have a greater ecological risk. We anticipate that our study can provide a basis for exploring the toxicity mechanisms of NPs and the environmental risk assessment of NPs.

Uptake and Effects of Nanoplastics on the Dinoflagellate Gymnodinium corollarium

Plastic nanoparticles (NPs) are the final state of plastic degradation in the environment before they disintegrate into low-molecular-weight organic compounds. Unicellular organisms are highly sensitive to the toxic effects of nanoplastics, because they are often capable of phagotrophy but are unable to consume a foreign material such as synthetic plastic. We studied the effect of polystyrene, poly(vinyl chloride), poly(methyl acrylate), and poly(methyl methacrylate) NPs on the photosynthetic dinoflagellate Gymnodinium corollarium Sundström, Kremp et Daugbjerg. Fluorescent tagged particles were used to visualize plastic capture by dinoflagellate cells. We found that these dinoflagellates are capable of phagotrophic nutrition and thus should be regarded as mixotrophic species. This causes their susceptibility to the toxic effects of plastic NPs. Living cells ingest plastic NPs and accumulate in the cytoplasm as micrometer-level aggregates, probably in food vacuoles. The action of nanoplastics leads to a dose-dependent increase in the level of reactive oxygen species in dinoflagellate cells, indicating plastic degradation in the cells. The introduction of a methyl group into the main chain in the α-position in the case of poly(methyl methacrylate) causes a drastic reduction in toxicity. We expect that such NPs can be a tool for testing unicellular organisms in terms of heterotrophic feeding ability. We suggest a dual role of dinoflagellates in the ecological fate of plastic waste: the involvement of nanoplastics in the food chain and its biochemical destruction. Environ Toxicol Chem 2023;42:1124-1133. © 2023 SETAC.

Nanoplastics potentiate mercury toxicity in a marine copepod under multigenerational exposure

The continuous fragmentation of plastics and release of synthetic nanoplastics from products have been aggravating nanoplastic pollution in the marine ecosystem. The carrier role of nanoplastics may increase the bioavailability and toxicity effects of toxic metals, e.g., mercury (Hg), which is of growing concern. Here, the copepod Tigriopus japonicus was exposed to polystyrene nanoplastics (PS NPs) and Hg (alone or combined) at environmental realistic concentrations for three generations (F0-F2). Then, Hg accumulation, physiological endpoints, and transcriptome were analyzed. The results showed that the copepod's reproduction was significantly inhibited under PS NPs or Hg exposure. The presence of PS NPs caused significantly higher Hg accumulation, lower survival, and lower offspring production in copepods relative to Hg exposure, suggesting an increased threat to the copepod's survivorship and health. From the molecular perspective, combined PS NPs and Hg caused a graver effect on the DNA replication, cell cycle, and reproduction pathways relative to Hg exposure, linking to lower levels of survivorship and reproduction. Taken together, this study provides an early warning of nanoplastic pollution for the marine ecosystem not only because of their adverse effect per se but also their carrier role for increasing Hg bioaccumulation and toxicity in copepods.

The heteroaggregation behavior of nanoplastics on goethite: Effects of surface functionalization and solution chemistry

Nanoplastics have attracted extensive attention in recent years. However, little is known about the heteroaggregation behavior of nanoplastics on goethite (FeOOH), especially the contribution of surface functional groups. In this study, the heteroaggregation behavior between polystyrene nanoplastics (PSNPs) and FeOOH was systematically investigated under different reaction conditions. Moreover, the effect of different functional groups (-NH₂, -COOH, and bare) of PSNPs and solution chemistry was evaluated. The results showed that PSNPs could heteroaggregate with FeOOH, and the heteroaggregation rate of PSNPs with surface functionalization was significantly faster. The removal of suspended PSNPs was enhanced with increasing NaCl or CaCl₂ concentration. However, heteroaggregation was significantly inhibited with the increase of solution pH. The zeta potentials analysis, time-resolved dynamic light scattering (DLS) and heteroaggregation experiments suggested that the electrostatic force affected the heteroaggregation process significantly. Fourier transform infrared (FTIR) spectra proved that the adsorption affinity between PSNPs and FeOOH was stronger after surface functionalization, especially for CH, O-C=O, and -CH₂- groups, indicating that chemical bonding also made a contribution during the heteroaggregation process. This work is expected to provide a theoretical basis for predicting the environmental behavior between PSNPs and FeOOH.

Potential lifetime effects caused by cellular uptake of nanoplastics: A review

Plastics have been used for about 100 years, and daily-use products composed of plastics are now prevalent. As a result, humans are very easily exposed to the plastic particles generated from the daily-use plastics. However, studies on cellular uptake of nanoplastics in "human cells" have only recently begun to attract attention. In previous studies, definitions of nanoplastics and microplastics were vague, but recently, they have been considered to be different and are being studied separately. However, nanoplastics, unlike plastic particles of other sizes such as macro- and microplastics, can be absorbed by human cells, and thus can cause various risks such as cytotoxicity, inflammation, oxidative stress, and even diseases such as cancer^{82, 83.} and diabetes (Fan et al., 2022; Wang et al., 2023). Thus, in this review, we defined microplastics and nanoplastics to be different and described the potential risks of nanoplastics to human caused by cellular uptake according to their diverse factors. In addition, during and following plastic product usage a substantial number of fragments of different sizes can be generated, including nanoplastics. Fragmentation of microplastics into nanoplastics may also occur during ingestion and inhalation, which can potentially cause long-term hazards to human health. However, there are still few in vivo studies conducted on the health effect of nanoplastics ingestion and inhalation.

Advances in the Utilization of Zebrafish for Assessing and Understanding the Mechanisms of Nano-/Microparticles Toxicity in Water

A large amount of nano-/microparticles (MNPs) are released into water, not only causing severe water pollution, but also negatively affecting organisms. Therefore, it is crucial to evaluate MNP toxicity and mechanisms in water. There is a significant degree of similarity between the genes, the central nervous system, the liver, the kidney, and the intestines of zebrafish and the human body. It has been shown that zebrafish are exceptionally suitable for evaluating the toxicity and action mechanisms of MNPs in water on reproduction, the central nervous system, and metabolism. Providing ideas and methods for studying MNP toxicity, this article discusses the toxicity and mechanisms of MNPs from zebrafish.

Tracking nanoplastics in freshwater microcosms and their impacts to aquatic organisms

In this work, we used palladium-doped polystyrene NPLs (PS-NPLs with a primary size of 286 ± 4 nm) with an irregular surface morphology which allowed for particle tracking and evaluation of their toxicity on two primary producers (cyanobacterium, Anabaena sp. PCC7120 and green algae, Chlamydomonas reinhardtii) and one primary consumer (crustacean, Daphnia magna). the concentration range for Anabaena and C. reinhardtii was from 0.01 to 1000 mg/L and for D. magna, the range was from 7.5 to 120 mg/L.EC_50 s ranged from 49 mg NPLs/L for D. magna (48hEC_50 s) to 248 mg NPLs/L (72hEC_50 s for C. reinhardtii). PS-NPLs induced dose-dependent reactive oxygen species overproduction, membrane damage and metabolic alterations. To shed light on the environmental fate of PS-NPLs, the short-term distribution of PS-NPLs under static (using lake water and sediments) and stirring (using river water and sediments) conditions was studied at laboratory scale. The results showed that most NPLs remained in the water column over the course of 48 h. The maximum percentage of settled particles (∼ 30 %) was found under stirring conditions in comparison with the ∼ 10 % observed under static ones. Natural organic matter increased the stability of the NPLs under colloidal state while organisms favored their settlement. This study expands the current knowledge of the biological effects and fate of NPLs in freshwater environments.

Evaluation of bioaccumulation of nanoplastics, carbon nanotubes, fullerenes, and graphene family materials

Bioaccumulation is a key factor in understanding the potential ecotoxicity of substances. While there are well-developed models and methods to evaluate bioaccumulation of dissolved organic and inorganic substances, it is substantially more challenging to assess bioaccumulation of particulate contaminants such as engineered carbon nanomaterials (CNMs; carbon nanotubes (CNTs), graphene family nanomaterials (GFNs), and fullerenes) and nanoplastics. In this study, the methods used to evaluate bioaccumulation of different CNMs and nanoplastics are critically reviewed. In plant studies, uptake of CNMs and nanoplastics into the roots and stems was observed. For multicellular organisms other than plants, absorbance across epithelial surfaces was typically limited. Biomagnification was not observed for CNTs and GFNs but were observed for nanoplastics in some studies. However, the reported absorption in many nanoplastic studies may be a consequence of an experimental artifact, namely release of the fluorescent probe from the plastic particles and subsequent uptake. We identify that additional work is needed to develop analytical methods to provide robust, orthogonal methods that can measure unlabeled (e.g., without isotopic or fluorescent labels) CNMs and nanoplastics.

Contamination from microplastics and other anthropogenic particles in the digestive tracts of the commercial species Engraulis encrasicolus and Sardina pilchardus

Fragments of microplastics (<5 mm) found in commercial species of fish, crustaceans, and bivalves, are an issue of global concern. The bioaccumulation of microplastics and other anthropogenic particles in different levels of the food web may provoke unwanted impacts on marine ecosystems and cause pernicious effects on human health. Here, we study the presence of anthropogenic particles and the fraction of microplastics in the target organs of two representative commercial fish species in Spain; the European anchovy (Engraulis encrasicolus) and the European pilchard (Sardina pilchardus). The individuals were sampled along the continental shelf of the Gulf of Cádiz, from the Bay of Cádiz to Cape Santa Maria. The isolation of the microplastics (MPs) was carried out with a complete alkaline-oxidant organic digestion (KOH-H₂O₂) of the digestive tract, including both the contents ingested and the muscle tissues. Anthropogenic particles were found in all individuals of both species with an average of 8.94 ± 5.11 items·ind^-1. Fibres made up 93 % of the items while fragments and films were represented by the remaining 7 %. The average size of the anthropogenic particles was 0.89 ± 0.82 mm. In addition to the fragment and film particles identified as microplastics, 29 % of the fibres were estimated to be microplastics by Fourier-transform infrared spectroscopy (FTIR) analysis. The main polymer found in both species was nylon. No significant correlation was found between the abundance and size of anthropogenic particles ingested and individual size or other body variables. The analysis of similarities (ANOSIM) and the distanced-based multiple linear regression model showed a high homogeneity in anthropogenic particle contamination in both species throughout the study area along the continental shelf of the Gulf of Cádiz.

Recent insights into uptake, toxicity, and molecular targets of microplastics and nanoplastics relevant to human health impacts

Microplastics and nanoplastics (M-NPLs) are ubiquitous environmentally, chemically, or mechanically degraded plastic particles. Humans are exposed to M-NPLs of various sizes and types through inhalation of contaminated air, ingestion of contaminated water and food, and other routes. It is estimated that Americans ingest tens of thousands to millions of M-NPLs particles yearly, depending on socioeconomic status, age, and gender. M-NPLs have spurred interest in toxicology because of their abundance, ubiquitous nature, and ability to penetrate bodily and cellular barriers, producing toxicological effects in cells, tissues, organs, and organ systems. The present review paper highlights: (1) The current knowledge in understanding the detrimental effects of M-NPLs in mouse models and human cell lines, (2) cellular organelle localization of M-NPLs, and the underlying uptake mechanisms focusing on endocytosis, (3) the possible pathways involved in M-NPLs toxicity, particularly reactive oxygen species, nuclear factor-erythroid factor 2-related factor 2 (NRF2), Wnt/β-Catenin, Nuclear Factor Kappa B (NF-kB)-regulated inflammation, apoptosis, and autophagy signaling. We also highlight the potential role of M-NPLs in increasing the incubation time, spread, and transport of the COVID-19 virus. Finally, we discuss the future prospects in this field.

Polystyrene nanoplastics enhance the toxicological effects of DDE in zebrafish (Danio rerio) larvae

Anthropogenic releases of plastics, persistent organic pollutants (POPs), and heavy metals can impact the environment, including aquatic ecosystems. Nanoplastics (NPs) have recently emerged as pervasive environmental pollutants that have the ability to adsorb POPs and can cause stress in organisms. Among POPs, DDT and its metabolites are ubiquitous environmental pollutants due to their long persistence. Despite the discontinued use of DDT in Europe, DDT and its metabolites (primarily p,p'-DDE) are still found at detectable levels in fish feed used in salmon aquaculture. Our study aimed to look at the individual and combined toxicity of NPs (50 mg/L polystyrene) and DDE (100 μg/L) using zebrafish larvae as a model. We found no significant morphological, cardiac, respiratory, or behavioural changes in zebrafish larvae exposed to NPs alone. Conversely, morphological, cardiac and respiratory alterations were observed in zebrafish larvae exposed to DDE and NPs + DDE. Interestingly, behavioural changes were only observed in zebrafish larvae exposed to NPs + DDE. These findings were supported by RNA-seq results, which showed that some cardiac, vascular, and immunogenic pathways were downregulated only in zebrafish larvae exposed to NPs + DDE. In summary, we found an enhanced toxicological impact of DDE when combined with NPs.

The toxic differentiation of micro- and nanoplastics verified by gene-edited fluorescent Caenorhabditis elegans

The increased emission and accumulation of micro- or nanoplastics (M-NPs) have posed a severely threaten to organisms in the environment. Though the toxicity of M-NPs has been observed in many species, the fundamental factors determining the biotoxicity are rarely expounded on. In this work, typical polystyrene (PS) M-NPs were set up with a multiparameter variation in size gradient, surface charge contrast and concentration variant, and evaluated by the Caenorhabditis elegans (C. elegans) model. From the endpoints of body length, brood size, survival rate and lifespan, an adverse effect was found on the growth and development of C. elegans caused by PSs. In general, the toxicity of PS was found to be concentrated- and size-dependent, with 100 nm positively charged nano-PS having the highest physio-toxicity. Monitoring by fluorescent imaging, it showed that positively charged nano-PS was mainly ingested and accumulated in the intestinal tract of C. elegans. In addition, the penetrated PS induced severe biological stress reactions with the increase of reactive oxygen species (ROS) and lipofuscin. Furthermore, the following expression of antioxidation-related enzymes was activated in vivo as indicated by the GFP-labelled C. elegans. All the results supplied visually toxic parameters of M-NPs to organisms, which sheds light on the biosecurity and ecological risks of M-NPs in the future.

Recognition and movement of polystyrene nanoplastics in fish cells

Although nanoplastics are being increasingly scrutinized, little is known about their kinetic behavior in living organisms, especially in cellular systems. Herein, nonspecific interactions of three polystyrene nanoplastics (pristine-PS, NH₂-PS, and COOH-PS, with size range of 90-100 nm and at concentrations of 0-100 μg mL^-1) with zebrafish cells were quantified for their cellular uptake and exocytosis. Cell uptake of nanoplastics reached a peak within 2 h and then decreased. The overall nanoplastics uptake was dominated by PS-particle internalization. The estimated uptake rate was comparable among the different types of PS (pristine-PS, NH₂-PS, and COOH-PS), but the uptake capacity was related to their functionality. The clathrin-mediated and caveolae-mediated pathways were mainly involved in the uptake of the three nanoplastics. The internalized PS-particles were initially delivered to the cytoplasm but then transported to lysosomes using energy. Meanwhile, these PS particles were released by the cells via energy-free penetration and energy-dependent lysosomal exocytosis. PS-particles were removed by the cells at a relatively slow rate, and the estimated retention half-lives of these PS-particles were 10.1 h, 12.0 h and 15.1 h for pristine-PS, NH₂-PS and COOH-PS particles, respectively, in fish cells based on our kinetic measurements. Intracellular trajectory modeling of nanoplastics movement is critical for the environmental and human health risk assessment.

Hazard of polystyrene micro-and nanospheres to selected aquatic and terrestrial organisms

Plastics contamination in the environment is a major concern. Risk assessment of micro- and nanoplastics (MPL and NPL) poses significant challenges due to MPL and NPL heterogeneity regarding compositional polymers, particle sizes and morphologies in the environment. Yet, there exists considerable toxicological literature on commercial polystyrene (PS) micro- and nanospheres. Although such particles do not directly represent the environmental MPL and NPL, their toxicity data should be used to advance the hazard assessment of plastics. Here, toxicity data of PS micro- and nanospheres for microorganisms, aquatic and terrestrial invertebrates, fish, and higher plants was collected and analyzed. The evaluation of 294 papers revealed that aquatic invertebrates were the most studied organisms, nanosized PS was studied more often than microsized PS, acute exposures prevailed over chronic exposures, the toxicity of PS suspension additives was rarely addressed, and ∼40 % of data indicated no organismal effects of PS. Toxicity mechanisms were mainly studied in fish and nematode Caenorhabditis elegans, providing guidance for relevant studies in higher organisms. Future studies should focus on environmentally relevant plastics concentrations, wide range of organisms, co-exposures with other pollutants, and method development for plastics identification and quantification to fill the gap of bioaccumulation assessment of plastics.

Potential Artifacts and Control Experiments in Toxicity Tests of Nanoplastic and Microplastic Particles

To fully understand the potential ecological and human health risks from nanoplastics and microplastics (NMPs) in the environment, it is critical to make accurate measurements. Similar to past research on the toxicology of engineered nanomaterials, a broad range of measurement artifacts and biases are possible when testing their potential toxicity. For example, antimicrobials and surfactants may be present in commercially available NMP dispersions, and these compounds may account for toxicity observed instead of being caused by exposure to the NMP particles. Therefore, control measurements are needed to assess potential artifacts, and revisions to the protocol may be needed to eliminate or reduce the artifacts. In this paper, we comprehensively review and suggest a next generation of control experiments to identify measurement artifacts and biases that can occur while performing NMP toxicity experiments. This review covers the broad range of potential NMP toxicological experiments, such as in vitro studies with a single cell type or complex 3-D tissue constructs, in vivo mammalian studies, and ecotoxicity experiments testing pelagic, sediment, and soil organisms. Incorporation of these control experiments can reduce the likelihood of false positive and false negative results and more accurately elucidate the potential ecological and human health risks of NMPs.

Combined effects of micro-/nano-plastics and oxytetracycline on the intestinal histopathology and microbiome in zebrafish (Danio rerio)

Accumulated evidence has demonstrated that microplastics and oxytetracycline (OTC) affect organisms, but few studies have investigated their combined effects on aquatic organisms. In this study, adult zebrafish (Danio rerio) were exposed to single and binary-combined contamination of micro-, nano-sized polystyrene plastics and OTC for 30 days, and the intestinal histopathology, gut microbiota and antibiotic resistance genes (ARGs) of zebrafish were measured. The results showed that the intestinal epithelial damage increase with the decrease of plastic sizes. Nano-sized plastics, OTC and their combined exposure caused intestinal epithelial damage, and co-exposure with micro-sized plastics reduced the intestinal damage caused by single OTC exposure. The gut microbial communities were affected by the combined exposure to microplastics and OTC. Compared with the blank control, the relative abundance of Fusobacteria increased 12.7 % and 21.1 % in OTC combined with 45-85 μm micro-plastics (MOTC) and 40-54 nm nano-plastics (NOTC), respectively, and that of Bacteroidetes increased 26.2 % and 18.6 % in the MOTC and NOTC treatments, respectively. The effects of MOTC and NOTC on the biodiversity of the zebrafish gut microbiome were different; MOTC increased the biodiversity by 11.3 % compared with the blank control, whereas NOTC decreased the biodiversity by 8.8 % compared with the blank control. Furthermore, the abundance of ARGs in 40-54 nm nano-plastics, MOTC and NOTC treatments was increased 96.9 %, 96.6 % and 68.8 % compared with the control group, respectively. Additionally, significant differences were observed in ARGs characteristics between the micro- and nano-plastics treated groups whether combined with OTC or not. These results are essential to further understand the combined ecotoxicological effects of micro- or nano-plastics and antibiotics on aquatic organisms.

Antagonistic in vivo interaction of polystyrene nanoplastics and silver compounds. A study using Drosophila

Since heavy metals and micro-/nanoplastics (MNPLs) can share common environmental niches, their potential interactions could modulate their hazard impacts. The current study was planned to evaluate the potential interactions between silver compounds (silver nanoparticles or silver nitrate) and two different sizes of polystyrene nanoplastics (PSNPLs) (PS-50 and PS-500 nm), administered via ingestion to Drosophila larvae. While egg-to-adult survival was not affected by the exposure to silver compounds, PSNPLs, or their coexposures, the combined treatments succeeded to restore the delay of fly emergence induced by silver compounds. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) showed the ability of PSNPLs to transport silver compounds (regardless of their form) across the intestinal barrier, delivering them into the hemolymph of Drosophila larvae in a concentration exceeding that mediated by the exposure to silver compounds alone. The molecular response (gene expression) of Drosophila larvae greatly fluctuated, accordingly if exposures were administered alone or in combination. Although PSNPLs produced some oxidative stress in the hemocytes of Drosophila, especially at the highest dose (1 mM), higher levels were observed after silver exposure, regardless of its form. Interestingly, the oxidative stress of silver, especially that produced by nano‑silver, drastically decreased when coexposed with PSNPLs. Similar effects were observed regarding the DNA damage induced in Drosophila hemocytes, where cotreatment decreased the genotoxicity induced by silver compounds. This antagonistic interaction could be attributed to the ability of tiny plastic specks to confine silver, avoiding its bioavailability, and diminishing their potential impacts.

Combined exposure to nanoplastics and metal oxide nanoparticles inhibits efflux pumps and causes oxidative stress in zebrafish embryos

The ubiquity of microplastic/nanoplastics (MP/NPs) provides an opportunity for their interaction with other widely spread environmental contaminants. MP/NP and nanoparticles share a similar transport route from sources, production, and disposal. Metal oxide nanoparticles (nMOx) have varied industrial applications, and limited knowledge is available on their interaction with MP/NPs. The present study investigated the effect of NPs (1 mg/L) on the efflux of two nMOx, aluminium oxide nanoparticles (nAl₂O₃, 1 mg/L) and cerium oxide nanoparticles (nCeO₂, 1 mg/L), and their combined toxicity to zebrafish embryos. The results illustrated increased accumulation of aluminium and cerium in the combined exposure group compared to the nMOx alone treatment. The presence of NPs exacerbated the oxidative stress caused by nAl₂O₃ and nCeO₂, as evidenced by an increase in the concentration of reactive oxygen species (ROS), alteration of antioxidants, and lipid peroxidation. The integrated biomarker response (IBRv2) values showed the induction of an antioxidative response in NP + nAl₂O₃, whereas a decline in IBRv2 values was observed in NP + nCeO₂. Our results indicate that NPs aggravated the accumulation of nMOx and their toxicity. The present work highlights that more attention should be paid to the discharge of these contaminants into the natural environment.