Functionalized Nanoplastics (NPs) Increase the Toxicity of Metals in Fish Cell Lines

Effects of single and combined exposure of virgin or aged polyethylene microplastics and penthiopyrad on zebrafish (Danio rerio)

The interaction between pesticides and microplastics (MPs) can lead to changes in their mode of action and biological toxicity, creating substantial uncertainty in risk assessments. Succinate dehydrogenase inhibitor (SDHI) fungicides, a common fungicide type, are widely used. However, little is known about how penthiopyrad (PTH), a member of the SDHI fungicide group, interacts with polyethylene microplastics (PE-MPs). This study primarily investigates the individual and combined effects of virgin or aged PE-MPs and penthiopyrad on zebrafish (Danio rerio), including acute toxicity, bioaccumulation, tissue pathology, enzyme activities, gut microbiota, and gene expression. Short-term exposure revealed that PE-MPs enhance the acute toxicity of penthiopyrad. Long-term exposure demonstrated that PE-MPs, to some extent, enhance the accumulation of penthiopyrad in zebrafish, leading to increased oxidative stress injury in their intestines by the 7th day. Furthermore, exposure to penthiopyrad and/or PE-MPs did not result in histopathological damage to intestinal tissue but altered the gut flora at the phylum level. Regarding gene transcription, penthiopyrad exposure significantly modified the expression of pro-inflammatory genes in the zebrafish gut, with these effects being mitigated when VPE or APE was introduced. These findings offer a novel perspective on environmental behavior and underscore the importance of assessing the combined toxicity of PE-MPs and fungicides on organisms.

Impacts of extracellular polymeric substances on the behaviors of micro/nanoplastics in the water environment

Increasing pollution of microplastics (MPs) and nanoplastics (NPs) has caused widespread concern worldwide. Extracellular polymeric substances (EPS) are natural organic polymers mainly produced by microorganisms, the major components of which are polysaccharides and proteins. This review focuses on the interactions that occur between EPS and MPs/NPs in the water environment and evaluates the effects of these interactions on the behaviors of MPs/NPs. EPS-driven formation of eco-corona, biofilm, and "marine snow" can incorporate MPs and NPs into sinking aggregates, resulting in the export of MPs/NPs from the upper water column. EPS coating greatly enhances the adsorption of metals and organic pollutants by MPs due to the larger specific surface area and the abundance of functional groups such as carboxyl, hydroxyl and amide groups. EPS can weaken the physical properties of MPs. Through the synergistic action of different extracellular enzymes, MPs may be decomposed into oligomers and monomers that can enter microbial cells for further mineralization. This review contributes to a comprehensive understanding of the dynamics of MPs and NPs in the water environment and the associated ecological risks.

Unveiling the Modification of Esterase-like Activity of Serum Albumin by Nanoplastics and Their Cocontaminants

Nanoplastics and other cocontaminants have raised concerns due to their widespread presence in the environment and their potential to enter the food chain. The harmful effects of these particles depend on various factors, such as nanoparticle size, shape, surface charge, and the nature of the cocontaminants involved. On entering the human body, human serum albumin (HSA) molecules bind and transport these particles in the blood system. The esterase-like activity of HSA, which plays a role in metabolizing drug/toxic compounds, was taken as a representative to portray the effects of these particles on HSA. Polystyrene nanoplastics (PSNPs) with different surface functionalization (plain (PS), amine (PS-NH2), and carboxy (PS-COOH)), different sizes (100 and 500 nm), and PS with cocontaminant metformin hydrochloride (Met-HCl), a widely used antidiabetic drug, were investigated in this study. Fluorescence emission spectra of HSA revealed that PS-NH2 exhibits a greater effect on protein conformation, smaller NPs have a greater influence on protein structure than larger NPs, and Met-HCl lowers PSNPs' affinity for HSA by coating the surface of the NPs, which may result in direct NP distribution to the drug's target organs and toxicity. Circular dichroism spectra also supported these results in terms of secondary structural changes. Esterase activity of HSA was inhibited by all the particles (except Met-HCl) by competitive inhibition as concluded from constant Vmax and increasing Km. Greater reduction in enzyme activity was observed for PS-NH2 among functionalizations and for 100 nm PS among sizes. Furthermore, Met-HCl lowers the inhibitory impact of PSNPs on HSA since the drug binds weakly to HSA, and so they can serve as a vector delivering PSNPs to their target organs, resulting in serious implications.

Does functionalised nanoplastics modulate the cellular and physiological responses of aquatic fungi to metals?

Co-contamination of freshwaters by nanoplastics (NPs; ≤ 1 μm) and metals is an emerging concern. Aquatic hyphomycetes play a crucial role as primary decomposers in these ecosystems. However, concurrent impacts of NPs and metals on the cellular and physiological activities of these fungi remain poorly understood. Here, the effects of environmentally realistic concentrations of two types of polystyrene (PS) NPs (bare and -COOH; up to 25 μg L-1) and copper (Cu; up to 50 μg L-1) individually and all possible combinations (NPs types and Cu) on Articulospora tetracladia, a prevalent aquatic hyphomycete, were investigated. Endpoints measured were intracellular reactive oxygen species accumulation, plasma membrane disruption and fungal growth. The results suggest that functionalised (-COOH) NPs enhance Cu adsorption, as revealed by spectroscopic analyses. Notably, NPs, Cu and their co-exposure to A. tetracladia can lead to ROS accumulation and plasma membrane disruption. In most cases, exposure to treatments containing -COOH NPs with Cu showed greater cellular response and suppressed fungal growth. By contrast, exposure to Cu individually showed stimulatory effects on fungal growth. Overall, this study provides novel insight that functionalisation of NPs facilitates metal adsorption, thus modulating the impacts of metals on aquatic fungi.

Molecular Interaction of Functionalized Nanoplastics with Human Hemoglobin

Humans are exposed to excessive nanoplastics (NPs) which have ample affinity for globular proteins. We investigated the interaction of functionalized polystyrene nanoplastics (plain: PS, carboxy: PS-COOH, and amine: PS-NH2) with human hemoglobin (Hb) utilizing multi-spectroscopic and docking approaches to acquire insights into molecular aspects of binding mechanism, which will be helpful in assessing the toxicokinetics or toxicodynamics of nanoplastics NPs. Hypsochromicity and hypochromicity were observed invariably in all the spectra (steady-state fluorescence emission, synchronous and three-dimensional) for all complexes, among which PS-NH2 binds effectively and changes the Hb's conformation by enhancing hydrophobicity around aromatic residues, notably tryptophan. All the NPs bind with the hydrophobic pocket of B-chain in Hb, where PS and PS-NH2 bind via hydrophobic force while PS-COOH binds via hydrogen bonding (predominantly) and van der Waals force, consistent validated with docking results. The minimal shift in absorbance peak also indicates enhanced hydrophobicity by PS-NH2 with larger aggregation as demonstrated in resonance light scattering. The amide band's shift, secondary structural analysis, and presence of characteristic functional group peaks in complexes in Infra-Red spectra confirm the structural changes in the protein. As seen in field emission scanning microscopy images, NPs penetrate the surface of proteins. These findings conclude that polystyrene NPs interact with Hb, causing structural alterations that may affect functional characteristics as well, with the greatest effect being in the order: PS-NH2>PS-COOH>PS.

Application of transcriptomic profiling to investigate the toxicity mechanisms caused by dietary exposure of nanoplastics in fish

Nowadays, nanoplastics (NPs) are one of the main concerns regarding plastic pollution. The increasing presence of plastic particles, fibers and fragments in the marine environment pose an additional risk to both, wild and cultured fish. Ingestion is the main mechanism by which particles are internalized. Thus, this study evaluated the impact of a diet containing NPs in one of the most cultivated species across the Mediterranean Sea, the European sea bass (Dicentrarchus labrax). Polystyrene NPs (50 nm) were supplied in the food for a period of 21 days and the transcriptomic changes were measured in the intestine through RNA-seq. Additionally, enzymatic and bactericidal activities were measured in the liver or serum, respectively of the same fish to evaluate the organism stress. No significant changes in the enzymatic activities were observed in the liver, whilst the seric bactericidal activity decreased by NPs dietary treatments. This suggests that ingestion of NPs at low dosages might have an impact on fish health. In addition, our data suggested that NPs impact some important biological pathways related to fish morphogenesis, organ development, membrane receptors, and fish immunity. These routes are extremely important for fish development and growth and can have long-term impact, since the early stages of fish are the most sensitive to this kind of pollution. This study provides information on the impact of the ingestion of NPs in sea bass and can serve as a basis for future investigations on the prevention and treatment of such pollutants in aquaculture.

Journey of micronanoplastics with blood components

The entry of micro- and nanoplastics (MNPs) into the human body is inevitable. They enter blood circulation through ingestion, inhalation, and dermal contact by crossing the gut-lung-skin barrier (the epithelium of the digestive tract, the respiratory tract, and the cutaneous layer). There are many reports on their toxicities to organs and tissues. This paper presents the first thorough assessment of MNP-driven bloodstream toxicity and the mechanism of toxicity from the viewpoint of both MNP and environmental co-pollutant complexes. Toxic impacts include plasma protein denaturation, hemolysis, reduced immunity, thrombosis, blood coagulation, and vascular endothelial damage, among others, which can lead to life-threatening diseases. Protein corona formation, oxidative stress, cytokine alterations, inflammation, and cyto- and genotoxicity are the key mechanisms involved in toxicity. MNPs change the secondary structure of plasma proteins, thereby preventing their transport functions (for nutrients, drugs, oxygen, etc.). MNPs inhibit erythropoiesis by influencing hematopoietic stem cell proliferation and differentiation. They cause red blood cell and platelet aggregation, as well as increased adherence to endothelial cells, which can lead to thrombosis and cardiovascular disease. White blood cells and immune cells phagocytose MNPs, provoking inflammation. However, research gaps still exist, including gaps regarding the combined toxicity of MNPs and co-pollutants, toxicological studies in human models, advanced methodologies for toxicity analysis, bioaccumulation studies, inflammation and immunological responses, dose-response relationships of MNPs, and the effect of different physiochemical characteristics of MNPs. Furthermore, most studies have analyzed toxicity using prepared MNPs; hence, studies must be undertaken using true-to-life MNPs to determine the real-world scenario. Additionally, nanoplastics may further degrade into monomers, whose toxic effects have not yet been explored. The research gaps highlighted in this review will inspire future studies on the toxicity of MNPs in the vascular/circulatory systems utilizing in vivo models to enable more reliable health risk assessment.

Response of moulting genes and gut microbiome to nano-plastics and copper in juvenile horseshoe crab Tachypleus tridentatus

Nanoplastics (NPs) and heavy metals are typical marine pollutants, affecting the gut microbiota composition and molting rate of marine organisms. Currently, there is a lack of research on the toxicological effects of combined exposure to horseshoe crabs. In this study, we investigated the effects of NPs and copper on the expression of molt-related genes and gut microbiome in juvenile tri-spine horseshoe crabs Tachypleus tridentatus by exposing them to NPs (100 nm, 104 particles L-1) and/or Cu2+ (10 μgL-1) in seawater for 21 days. Compared with the control group, the relative mRNA expression of ecdysone receptor (EcR), retinoid x receptor (RXR), calmodulin-A-like isoform X1 (CaM X1), and heat shock 70 kDa protein (Hsp70) were significantly increased under the combined stress of NPs and Cu2+. There were no significant differences in the diversity and abundance indices of the gut microbial population of horseshoe crabs between the NPs and/or Cu2+ groups and the control group. According to linear discriminant analysis, Oleobacillus was the most abundant microorganism in the NPs and Cu2+ stress groups. These results indicate that exposure to either NPs stress alone or combined NPs and Cu2+ stress can promote the expression levels of juvenile molting genes. NPs exposure has a greater impact on the gut microbial community structure of juvenile horseshoe crabs compared to Cu2+ exposure. This study is helpful for predicting the growth and development of horseshoe crabs under complex environmental pollution.

Toxicological impact of microplastics and nanoplastics on humans: understanding the mechanistic aspect of the interaction

Plastic is a pervasive material that has become an indispensable part of our daily lives and is used in various commercial products. However, plastic waste has significantly impacted the environment, accumulating in water and land ecosystems and harming all forms of life. When plastic degrades, it breaks down into smaller particles called microplastics (MPs), which can further breakdown into nanoplastics (NPs). Due to their small size and potential toxicity to humans, NPs are of particular concern. During the COVID-19 pandemic, the production of plastic had reached unprecedented levels, including essential medical kits, food bags, and personal protective equipment (PPE), which generate MPs and NPs when burned. MPs and NPs have been detected in various locations, such as air, food, and soil, but our understanding of their potential adverse health effects is limited. This review aims to provide a comprehensive overview of the sources, interactions, ecotoxicity, routes of exposure, toxicity mechanisms, detection methods, and future directions for the safety evaluation of MPs and NPs. This would improve our understanding of the impact of MPs and NPs on our health and environment and identify ways to address this global crisis.

Nanoplastic uptake temporarily affects the pulsing behavior in ephyrae of the moon jellyfish Aurelia sp

The aim of this study is to investigate for the first time the uptake and ecotoxicological effects of nanoplastics (NPs) in a marine cnidarian. Ephyrae of the moon jellyfish Aurelia sp. of different ages (0 and 7 days old) were exposed to negatively charged polystyrene NPs for 24 h; then, the uptake was assessed through traditional and novel techniques, namely microscopy and three-dimensional (3D) holotomography. Immobility and behavioral responses (frequency of pulsations) of ephyrae were also investigated to clarify if NP toxicity differed along the first life stages. NP uptake was observed in ephyrae thanks to the 3D technique. Such internalization did not affect survival, but it temporarily impaired the pulsation mode only in 0 day old ephyrae. This may be ascribed to the negative charged NPs, contributing to jellyfish behavioral alteration. These findings promote 3D holotomography as a suitable tool to detect NPs in marine organisms. Moreover, this study recommends the use of cnidarians of different ages to better assess NP ecotoxicological effects in these organisms, key components of the marine food web.

From marine to freshwater environment: A review of the ecotoxicological effects of microplastics

Microplastics (MPs) have been widely detected in the world's water, which may pose a significant threat to the ecosystem as a whole and have been a subject of much attention because their presence impacts seas, lakes, rivers, and even the Polar Regions. There have been numerous studies that report direct adverse effects on marine organisms, but only a few have explored their ecological effects on freshwater organisms. In this field, there is still a lack of a systematic overview of the toxic effects and mechanisms of MPs on aquatic organisms, as well as a consistent understanding of the potential ecological consequences. This review describes the fate and impact on marine and freshwater aquatic organisms. Further, we examine the toxicology of MPs in order to uncover the relationship between aquatic organism responses to MPs and ecological disorders. In addition, an overview of the factors that may affect the toxicity effects of MPs on aquatic organisms was presented along with a brief examination of their identification and characterization. MPs were discussed in terms of their physicochemical properties in relation to their toxicological concerns regarding their bioavailability and environmental impact. This paper focuses on the progress of the toxicological studies of MPs on aquatic organisms (bacteria, algae, Daphnia, and fish, etc.) of different trophic levels, and explores its toxic mechanism, such as behavioral alternations, metabolism disorders, immune response, and poses a threat to the composition and stability of the ecosystem. We also review the main factors affecting the toxicity of MPs to aquatic organisms, including direct factors (polymer types, sizes, shapes, surface chemistry, etc.) and indirect factors (persistent organic pollutants, heavy metal ions, additives, and monomer, etc.), and the future research trends of MPs ecotoxicology are also pointed out. The findings of this study will be helpful in guiding future marine and freshwater rubbish studies and management strategies.

Ecotoxicity of Heteroaggregates of Polystyrene Nanospheres in Chironomidae and Amphibian

Due to their various properties as polymeric materials, plastics have been produced, used and ultimately discharged into the environment. Although some studies have shown their negative impacts on the marine environment, the effects of plastics on freshwater organisms are still poorly studied, while they could be widely in contact with this pollution. The current work aimed to better elucidate the impact and the toxicity mechanisms of two kinds of commercial functionalized nanoplastics, i.e., carboxylated polystyrene microspheres of, respectively, 350 and 50 nm (PS350 and PS50), and heteroaggregated PS50 with humic acid with an apparent size of 350 nm (PSHA), all used at environmental concentrations (0.1 to 100 µg L^-1). For this purpose, two relevant biological and aquatic models-amphibian larvae, Xenopus laevis, and dipters, Chironomus riparius-were used under normalized exposure conditions. The acute, chronic, and genetic toxicity parameters were examined and discussed with regard to the fundamental characterization in media exposures and, especially, the aggregation state of the nanoplastics. The size of PS350 and PSHA remained similar in the Xenopus and Chironomus exposure media. Inversely, PS50 aggregated in both exposition media and finally appeared to be micrometric during the exposition tests. Interestingly, this work highlighted that PS350 has no significant effect on the tested species, while PS50 is the most prone to alter the growth of Xenopus but not of Chironomus. Finally, PSHA induced a significant genotoxicity in Xenopus.

Di-(2-ethylhexyl) phthalate exacerbated the toxicity of polystyrene nanoplastics through histological damage and intestinal microbiota dysbiosis in freshwater Micropterus salmoides

Organic pollutants such as di-(2-ethylhexyl) phthalate (DEHP) interact with nanoplastics (NPs) and change their bioavailability and toxicity to aquatic organisms. This study aims to assess the ecotoxicological impacts of NPs in the presence and absence of DEHP on juvenile largemouth bass (LMB) Micropterus salmoides. Therefore, LMB was fed with diets containing various concentrations (0, 2, 10, and 40 mg/g) of polystyrene nanoplastics (PSNPs) by the weight of diets. After a 21-day of PSNPs dietary exposure, LMB was treated with DEHP at 450 μg/L through waterborne exposure for three days. Our results showed that PSNPs were accumulated in the intestinal tissues, which significantly decreased the feeding and growth rates in LMB. The histopathological analysis showed the intestine and liver of LMB were subjected to various degrees of structural damage caused by PSNPs, and DEHP-PSNP co-exposure enhanced those histopathological damages in both tissues. Additionally, the co-exposure induced oxidative stress in terms of increased activities of glutathione S-transferase, catalase, and superoxide dismutase enzymes in the liver, intestine, spleen, and serum. Furthermore, the co-exposure significantly changed the intestinal microbial composition, i.e., the decrease in the abundance of probiotics (Bacteroidetes and Proteobacteria) and the increase in pathogenic bacteria (Firmicutes) posed a great threat to fish metabolism and health. Therefore, this study highlights that the presence of DEHP enhances the toxicity of NPs on LMB in freshwater and suggests the regulated use of plastic and its additives for improving the health status of aquaculture fish for food safety in humans.

Reduction in Toxicity of Polystyrene Nanoplastics Combined with Phenanthrene through Binding of Jellyfish Mucin with Nanoplastics

Mucin (Mu), a biological substance extracted from jellyfish (Aurelia aurita), was used to reduce the toxic effect of polystyrene nanoplastics (PS-NP) combined with phenanthrene (Phe) in the aquatic environment of zebrafish (Danio rerio), among other aquatic organisms. Mu showed a high binding capacity, as it bound to 92.84% and 92.87% of the PS-NPs (concentration of 2.0 mg/L) after 0.5 h and 8 h, respectively. A zebrafish embryo development test was conducted to check for any reduction in toxicity by Mu. When exposed to PS-NP + Mu and PS-NP + Phe + Mu, respectively, the hatching rates were 88.33 ± 20.21% and 93.33 ± 2.89%, respectively; these results were not significantly different from those of the control group. However, the hatching rate with the addition of Mu increased, compared to that of the PS-NP (71.83 ± 13.36%) and Phe (37.50 ± 19.83%) treatments, and the morphological abnormality rate decreased. The presence of Mu was also found to obstruct the absorption of PS-NP and PS-NP + Phe by the zebrafish. When zebrafish embryos were exposed to PS-NP at a concentration of 5.0 mg/L, the hatching rate differed significantly from that of the control group, and the expression of CAT and p53 genes increased significantly, but the expression of Bcl-2 decreased significantly. An mRNA sequence analysis revealed that the gene expression levels of the test group containing Mu were similar to those of the control group. These results infer that Mu can be used as a biological material to collect and remove PS-NPs from aquatic environments and reduce toxicity.

Environmentally Toxic Solid Nanoparticles in Noradrenergic and Dopaminergic Nuclei and Cerebellum of Metropolitan Mexico City Children and Young Adults with Neural Quadruple Misfolded Protein Pathologies and High Exposures to Nano Particulate Matter

Quadruple aberrant hyperphosphorylated tau, beta-amyloid, α-synuclein and TDP-43 neuropathology and metal solid nanoparticles (NPs) are documented in the brains of children and young adults exposed to Metropolitan Mexico City (MMC) pollution. We investigated environmental NPs reaching noradrenergic and dopaminergic nuclei and the cerebellum and their associated ultrastructural alterations. Here, we identify NPs in the locus coeruleus (LC), substantia nigrae (SN) and cerebellum by transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) in 197 samples from 179 MMC residents, aged 25.9 ± 9.2 years and seven older adults aged 63 ± 14.5 years. Fe, Ti, Hg, W, Al and Zn spherical and acicular NPs were identified in the SN, LC and cerebellar neural and vascular mitochondria, endoplasmic reticulum, Golgi, neuromelanin, heterochromatin and nuclear pore complexes (NPCs) along with early and progressive neurovascular damage and cerebellar endothelial erythrophagocytosis. Strikingly, FeNPs 4 ± 1 nm and Hg NPs 8 ± 2 nm were seen predominantly in the LC and SN. Nanoparticles could serve as a common denominator for misfolded proteins and could play a role in altering and obstructing NPCs. The NPs/carbon monoxide correlation is potentially useful for evaluating early neurodegeneration risk in urbanites. Early life NP exposures pose high risk to brains for development of lethal neurologic outcomes. NP emissions sources ought to be clearly recognized, regulated, and monitored; future generations are at stake.

In vitro cultivation of primary intestinal cells from Eisenia fetida as basis for ecotoxicological studies

The earthworm Eisenia fetida is a commonly used model organism for unspecific soil feeders in ecotoxicological studies. Its intestinal cells are the first to encounter possible pollutants co-ingested by the earthworm, which makes them prime candidates for studies of toxic effects of environmental pollutants on the cellular as compared to the organismic level. In this context, the aim of this study was to demonstrate the suitability of preparations of primary intestinal E. fetida cells for in vitro ecotoxicological studies. For this purpose, a suitable isolation and cultivation protocol was established. Cells were isolated directly from the intestine, maintaining >85% viability during subsequent cultivations (up to 144 h). Exposure to established pollutants and soil elutriates comprising silver nanoparticles and metal ions (Cu²⁺, Cd²⁺) induced a significant decrease in the metabolic activity of the cells. In case of microplastic particles (MP particles), namely 0.2, 0.5, 2.0, and 3.0 µm diameter polystyrene (PS) beads as well as 0.5 and 2.0 µm diameter polylactic acid (PLA) beads, no active uptake was observed. Slight positive as well as negative dose and size dependent effects on the metabolism were seen, which to some extent might correlate with effects on the organismic level.

Nanoplastics Increase Fish Susceptibility to Nodavirus Infection and Reduce Antiviral Immune Responses

Nanoplastics (NPs) might cause different negative effects on aquatic organisms at different biological levels, ranging from single cells to whole organisms, including cytotoxicity, reproduction, behavior or oxidative stress. However, the impact of NPs on disease resistance is almost unknown. The objective of this study was to assess whether exposure to 50 nm functionalized polystyrene NPs impacts fish susceptibility to viral diseases both in vitro and in vivo. In particular, we focused on the nervous necrosis virus (NNV), which affects many fish species, producing viral encephalopathy and retinopathy (VER), and causes great economic losses in marine aquaculture. In vitro and in vivo approaches were used. A brain cell line (SaB-1) was exposed to 1 μg mL⁻¹ of functionalized polystyrene NPs (PS-NH₂, PS-COOH) and then infected with NNV. Viral titers were increased in NP-exposed cells whilst the transcription of inflammatory and antiviral markers was lowered when compared to those cells only infected with NNV. In addition, European sea bass (Dicentrarchus labrax) juveniles were intraperitoneally injected with the same NPs and then challenged with NNV. Our results indicated that NPs increased the viral replication and clinical signs under which the fish died although the cumulate mortality was unaltered. Again, exposure to NPs produced a lowered inflammatory and antiviral response. Our results highlight that the presence of NPs might impact the infection process of NNV and fish resistance to the disease, posing an additional risk to marine organisms.

Uptake and toxicity of polystyrene micro/nanoplastics in gastric cells: Effects of particle size and surface functionalization

Toxicity of micro or nanoplastics (MP/NP) in aquatic life is well-documented, however, information about the consequences of exposure to these particles in terrestrial species is scarce. This study was used to evaluate the uptake and/or toxicity of polystyrene MP/NP in human gastric cells, comparing doses, particle sizes (50, 100, 200, 500, 1000 or 5000 nm) and surface functionalization (aminated, carboxylated or non-functionalized). In general, the uptake of 50 nm particles was significantly higher than 1000 nm particles. Among the 50 nm particles, the aminated particles were more avidly taken up by the cells and were cytotoxic at a lower concentration (≥ 7.5 μg/mL) compared to same sized carboxylated or non-functionalized particles (≥ 50 μg/mL). High toxicity of 50 nm aminated particles corresponded well with significantly high rates of apoptosis-necrosis induced by these particles in 4 h (29.2% of total cells) compared to all other particles (≤ 16.8%). The trend of apoptosis-necrosis induction by aminated particles in 4 h was 50 > 5000 > 1000 > 500 > 200 > 100 nm. The 50 nm carboxylated or non-functionalized particles also induced higher levels of apoptosis-necrosis in the cells compared to 100, 1000 and 5000 nm particles with same surface functionalization but longer exposure (24 h) to 50 nm carboxylated or non-functionalized particles significantly (p<0.0001) increased apoptosis-necrosis in the cells. The study demonstrated that the toxicity of MP/NP to gastric cells was dependent on particle size, dose surface functionalization and exposure period.