Aging of Copper Nanoparticles in the Marine Environment Regulates Toxicity for a Coastal Phytoplankton Species

Silver nanoparticles alter plankton-mediated carbon cycle processes in freshwater mesocosms

Understanding the ecological impacts of nanoparticle exposure has become increasingly urgent, as these materials are now widespread in aquatic environments. However, the effects of nanoparticle exposure on plankton community-mediated carbon cycling remain poorly understood. This study investigated the effects of long-term (28-day) exposure to environmentally relevant concentrations (10 and 100 µg/L) of silver nanoparticles (AgNPs) on the plankton-mediated carbon cycling processes of freshwater ecosystems by constructing a mesocosm ecosystem. The results showed that AgNP exposure enhanced the photosynthetic activity and biomass of both phytoplankton and zooplankton, thereby promoting carbon fixation. AgNP exposure also increased the ecological niche breadth and carbon source utilization of planktonic microorganisms while disrupting lipid metabolism, which facilitated carbon decomposition and utilization. Furthermore, AgNPs promoted the transformation of organic carbon by reducing the content and chemical composition of dissolved organic carbon and increasing the sedimentation of particulate organic carbon in the plankton community. Notably, compared with the control, exposure to 10 and 100 µg/L AgNPs reduced CO2 release at the water-air interface by 9 % and 17 %, respectively. Overall, this study provides the first evidence that long-term exposure to AgNPs can alter plankton-mediated carbon cycling processes in aquatic ecosystems, offering new insights into the ecotoxicological effects and risk assessment of nanoparticles.

Cytotoxicity of single and binary mixtures of copper and silica nanoparticles exposed to Nitzschia closterium f. minutissima

A large number of nanoparticles are produced and enter the aquatic environment, where they interact with each other, posing a potential threat to aquatic organisms. The toxicity of two types of nanoparticles (nCu and nSiO2) on Nitzschia closterium f. minutissima (N. closterium f. minutissima) was investigated in this study by examining changes in microalgal cell density, instantaneous fluorescence rate (Ft), and a range of antioxidant parameters in the cells. It was found that both nCu and nSiO2 showed time- and concentration-dependent toxic effects on N. closterium f. minutissima. nSiO2 could promote microalgae growth at low concentrations by providing Si, an essential element for the synthesis of siliceous shells. As the exposure time increased, both the growth and photosynthetic efficiency of the microalgae were inhibited. Nanoparticles also produced oxidative stress and caused lipid peroxidation in the microalgae. In the meantime, SOD and CAT activity were altered to protect cells from oxidative damage. Inverted biomicroscopy images showed that the microalgae enhanced their cell size to adapt to the environmental stress as exposed to 1 mg/L nCu. Scanning electron microscope (SEM) images showed that 10 mg/L nSiO2 could adsorb nCu and reduce the toxic effect of nCu on the microalgae, while 30 mg/L nSiO2 caused mechanical damage to microalgal cells and accelerated the internalization of nanoparticles and Cu2+ in the cells.

Impact of copper stress in the intestinal barriers and gut microbiota of Chinese stripe-necked turtle (Mauremys sinensis)

Copper is used to treat algal blooms, macrophyte infestations and other environmental issues, but its rising ambient levels harm aquatic animals, especially their intestines. However, its impact on turtles' digestive health is not well understood, and the risks are unclear. This study investigates the effects of copper on the intestinal health of Chinese stripe-necked turtle, focusing on histomorphology, mucosal barrier function, gene expression, and gut microbiota. Copper stress caused intestinal damage, characterized by shortened villi, inflammatory cell infiltration, and reduced epithelial layer thickness, as well as decreased acidic mucins, increased villi edema and inflammation. The mRNA expression level of bacteriostatic enzymes significantly reduced. Furthermore, This study found that copper exposure increases gut permeability by suppressing tight junction genes and triggers an inflammatory response in the gut, as indicated by elevated inflammatory cytokines. At the phylum level, Firmicutes exhibited a significant decrease, whereas Bacteroidota displayed a notable increase, and Fusobacteriota showed a substantial reduction in relative abundance in copper-treated groups. Similarly, at genus level Romboutsia, Cetobacterium decreased, while Turicibacter and Sarcina significantly increases in copper-treated groups compared to the control. This indicating the unique properties of copper including its essentiality, reactivity, and accumulation enables it to profoundly impact gut bacteria, altering both their composition and function. Copper's dual role as a nutrient and toxicant uniquely impacts gut microbes. Our findings suggest that copper stress compromises the intestinal physical, immune, chemical, and microbial barrier in M. sinensis, all of which contribute to the turtle's poor health.

MoS2 Nanosheets at Low Doses Induced Cardiotoxicity in Developing Zebrafish via Ferroptosis: Influence of Lateral Size and Surface Modification

The widespread applications of molybdenum disulfide (MoS2) nanosheets inevitably result in their release into aquatic environments, necessitating an exploration of their potential toxic effects on aquatic organisms. This study analyzes the cardiac responses of zebrafish larvae exposed to MoS2, with a focus on the influence of size and surface modifications. At higher concentrations (1 and 5 mg/L), MoS2 nanosheets hampered larval growth without influencing cardiomyogenesis. At lower doses (0.5-100 μg/L), small-sized MoS2 (ssMoS2, 187.2 nm) significantly impaired cardiac development, as proved by morphology abnormality, decreased heartbeat, stroke volume, and cardiac output, whereas these undesirable changes were not observed in the cysteine-modified form. Large-sized nanosheets (1.638 μm) did not localize to the heart, barely showing a cardiac disorder. Transcriptomics, biochemical analysis, and computational simulation validated that ssMoS2 aggravated Fe2+ overload through excessive ferritinophagy and ferroportin-1 inhibition, accompanied by down-regulation of glutathione peroxidase 4 and activation of PUFAs esterification, leading to ferroptosis. Significant associations between ferroptosis signals and cardiac indices, along with the ferrostatin-1 inhibition test, confirmed the ferroptosis-mediated cardiotoxicity of ssMoS2. Our study provides a key understanding of molecular events underlying MoS2-induced cardiotoxicity and highlights the importance of size and surface characteristics, which are significant for risk assessment and the safe design of nanoproducts.

Luminescent carbon dots-rooted polysaccharide crosslinked hydrogel adsorbent for sensitive determination and efficient removal of Cu2

In this study, a novel luminescent carbon dot-rooted polysaccharide hydrogel (CDs@CCP hydrogel) was prepared by crosslinking cellulose, chitosan (CS), and polyvinyl alcohol (PVA) for simultaneous fluorescent sensing and adsorption of Cu2+. The crosslinking of these low-cost, polysaccharide polymers greatly enhance the mechanical strength of the composite hydrogel while making the polysaccharide-based adsorbent easy to reuse. This composite hydrogel exhibited an excellent adsorption capacity (124.7 mg∙g-1) for residual Cu2+ in water, as well as a sensitive and selective fluorescence response towards Cu2+ with a good linear relationship (R2 > 0.97) and a low detection limit (LOD) of 0.02 μM. The adsorption isotherms, adsorption kinetics, and thermodynamics studies were also conducted to investigate the adsorption mechanism. This composite hydrogel offers an efficient tool for simultaneous monitoring and treatment of Cu2+ from wastewater.

An overview on dispersion procedures and testing methods for the ecotoxicity testing of nanomaterials in the marine environment

Considerable efforts have been devoted to develop or adapt existing guidelines and protocols, to obtain robust and reproducible results from (eco)toxicological assays on engineered nanomaterials (NMs). However, while many studies investigated adverse effects of NMs on freshwater species, less attention was posed to the marine environment, a major sink for these contaminants. This review discusses the procedures used to assess the ecotoxicity of NMs in the marine environment, focusing on the use of protocols and methods for preparing NMs dispersions and on the NMs physicochemical characterization in exposure media. To this purpose, a critical analysis of the literature since 2010 was carried out, based on the publication of the first NMs dispersion protocols. Among the 89 selected studies, only <5 % followed a standardized dispersion protocol combined with NMs characterization in ecotoxicological media, while more than half used a non-standardized dispersion method but performed NMs characterization. In the remaining studies, only partial or no information on dispersion procedures or on physicochemical characterization was provided. This literature review also highlighted that metal oxides NMs were the most studied (42 %), but with an increasing interest in last years towards nanoplastics (14 %) and multicomponent nanomaterials (MCNMs, 7 %), in line with the growing attention on these emerging contaminants. For all these NMs, primary producers as algae and bacteria were the most studied groups of marine species, in addition to mollusca, while organisms at higher trophic levels were less represented, likely due to challenges in evaluating adverse effects on more complex organisms. Thus, despite the wide use of NMs in different applications, standard dispersion protocols are not often used for ecotoxicity testing with marine species. However, the efforts to characterize NMs in ecotoxicological media recognize the importance of following conditions that are as standardized as possible to support the ecological hazard assessment of NMs.

Everything falls apart: How solids degrade and release nanomaterials, composite fragments, and microplastics

To ensure the safe use of materials, one must assess the identity and quantity of exposure. Solid materials, such as plastics, metals, coatings and cements, degrade to some extent during their life cycle, and releases can occur during manufacturing, use and end-of-life. Releases (e.g., what is released, how does release happen, and how much material is released) depend on the composition and internal (nano)structures of the material as well as the applied stresses during the lifecycle. We consider, in some depth, releases from mechanical, weathering and thermal stresses and specifically address the use cases of fused-filament 3D printing, dermal contact, food contact and textile washing. Solid materials can release embedded nanomaterials, composite fragments, or micro- and nanoplastics, as well as volatile organics, ions and dissolved organics. The identity of the release is often a heterogenous mixture and requires adapted strategies for sampling and analysis, with suitable quality control measures. Control materials enhance robustness by enabling comparative testing, but reference materials are not always available as yet. The quantity of releases is typically described by time-dependent rates that are modulated by the nature and intensity of the applied stress, the chemical identity of the polymer or other solid matrix, and the chemical identity and compatibility of embedded engineered nanomaterials (ENMs) or other additives. Standardization of methods and the documentation of metadata, including all the above descriptors of the tested material, applied stresses, sampling and analytics, are identified as important needs to advance the field and to generate robust, comparable assessments. In this regard, there are strong methodological synergies between the study of all solid materials, including the study of micro- and nanoplastics. From an outlook perspective, we review the hazard of the released entities, and show how this informs risk assessment. We also address the transfer of methods to related issues such as tyre wear, advanced materials and advanced manufacturing, biodegradable polymers, and non-solid matrices. As the consideration of released entities will become more routine in industry via lifecycle assessment in Safe-and-Sustainable-by-Design practices, release assessments will require careful design of the study with quality controls, the use of agreed-on test materials and standardized methods where these exist and the adoption of clearly defined data reporting practices that enable data reuse, meta-analyses, and comparative studies.

Toxicological effects of copper on bioaccumulation and mRNA expression of antioxidant, immune, and apoptosis-related genes in Chinese striped-necked turtle (Mauremys sinensis)

Heavy metals are among the most ubiquitous environmental pollutants of recent decades. Copper is commonly used to control algal blooms or macrophyte and waste infestations, its ambient concentration has increased significantly, indicating possible environmental risk. To investigate the effects of copper exposure on bioaccumulation, antioxidant defense, immune response, and apoptosis in the Chinese Striped-necked Turtle Mauremys sinensis, three experimental groups, control (0.0 mg/L), Cu2 (2 mg/L) and Cu4 (4 mg/L) were designed, and sampled at 14 and 28 days. Results showed that copper accumulates in different organs depending on the concentration and exposure time, Liver > Kidney > Gut > Heart > Brain > Muscle and the time order was 28 days > 14 days. The liver enzymes AST, ALT, and ALP decreased when the turtles were exposed to copper stress, while the contents of bilirubin TBIL, DBIL, IBIL, and LDH showed a significant upward trend. Similarly, the mRNA expression level of acetylcholinesterase AChE in the brain was significantly downregulated upon copper exposure. An upward trend was noticed in the liver Metallothionein MT mRNA expression levels compared to the control group. The mRNA expression levels of antioxidant enzymes CAT, SOD, MnSOD, and GSH-PX1 in the liver increased initially and then significantly decreased. Furthermore, the relative mRNA expression levels of inflammatory cytokines IL-1β, IL-8, TNF-α, and IFN-γ involved in inflammatory response significantly upregulated. Copper significantly increased the hepatic mRNA transcription of heat shock proteins HSP70 and HSP90 at different exposure durations. In addition, the relative mRNA levels of caspase3, caspase8, and caspase9 related to the caspase-dependent apoptotic pathway significantly increased under copper stress. These results explain that copper toxicity causes bioaccumulation, promotes oxidative stress, obstructs immunity, and induces inflammation and apoptosis by altering their gene expression levels in M. sinensis.

Detection, distribution and environmental risk of metal-based nanoparticles in a coastal bay

Metal-based nanoparticles (NPs) attract increasing concerns because of their adverse effects on aquatic ecosystems. However, their environmental concentrations and size distributions are largely unknown, especially in marine environments. In this work, environmental concentrations and risks of metal-based NPs were examined in Laizhou Bay (China) using single-particle inductively coupled plasma-mass spectrometry (sp-ICP-MS). First, separation and detection approaches of metal-based NPs were optimized for seawater and sediment samples with high recoveries of 96.7% and 76.3%, respectively. Spatial distribution results showed that Ti-based NPs had the highest average concentrations for all the 24 stations (seawater, 1.78 × 108 particles/L; sediments, 7.75 × 1012 particles/kg), followed by Zn-, Ag-, Cu-, and Au-based NPs. For all the NPs in seawater, the highest abundance occurred around the Yellow River Estuary, resulting from a huge input from Yellow River. In addition, the sizes of metal-based NPs were generally smaller in sediments than those in seawater (22, 20, 17, and 16 of 22 stations for Ag-, Cu-, Ti-, and Zn-based NPs, respectively). Based on the toxicological data of engineered NPs, predicted no-effect concentrations (PNECs) to marine species were calculated as Ag at 72.8 ng/L < ZnO at 2.66 µg/L < CuO at 7.83 µg/L < TiO2 at 72.0 µg/L, and the actual PNECs of the detected metal-based NPs may be higher due to the possible presence of natural NPs. Station 2 (around the Yellow River Estuary) was assessed as "high risk" for Ag- and Ti-based NPs with risk characterization ratio (RCR) values of 1.73 and 1.66, respectively. In addition, RCRtotal values for all the four metal-based NPs were calculated to fully assess the co-exposure environmental risk, with 1, 20, and 1 of 22 stations as "high risk", "medium risk", and "low risk", respectively. This study helps to better understand the risks of metal-based NPs in marine environments.