Nano-titanium dioxide induced genotoxicity and histological lesions in a tropical fish model, Nile tilapia (Oreochromis niloticus)

Single and combined effects of titanium (TiO2) and zinc (ZnO) oxide nanoparticles in the rainbow trout gill cell line RTgill-W1

Understanding the environmental impact of nanoparticle (NP) mixtures is essential to accurately assess the risk they represent for aquatic ecosystems. However, although the toxicity of individual NPs has been extensively studied, information regarding the toxicity of combined NPs is still comparatively rather scarce. Hence, this research aimed to investigate the individual and combined toxicity mechanisms of two widely consumed nanoparticles, zinc oxide (ZnO NPs) and titanium dioxide (TiO2 NPs), using an in vitro model, the RTgill-W1 rainbow trout gill epithelial cell line. Sublethal concentrations of ZnO NPs (0.1 µg mL-1) and TiO2 (30 µg mL-1) and a lethal concentration of ZnO NPs causing 10% mortality (EC10, 3 µg mL-1) were selected based on cytotoxicity assays. Cells were then exposed to the NPs at the selected concentrations alone and to their combination. Cytotoxicity assays, oxidative stress markers, and targeted gene expression analyses were employed to assess the NP cellular toxicity mechanisms and their effects on the gill cells. The cytotoxicity of the mixture was identical to the one of ZnO NPs alone. Enzymatic and gene expression (nrf2, gpx, sod) analyses suggest that none of the tested conditions induced a strong redox imbalance. Metal detoxification mechanisms (mtb) and zinc transportation (znt1) were affected only in cells exposed to ZnO NPs, while tight junction proteins (zo1 and cldn1), and apoptosis protein p53 were overexpressed only in cells exposed to the mixture. Osmoregulation (Na + /K + ATPase gene expression) was not affected by the tested conditions. The overall results suggest that the toxic effects of ZnO and TiO2 NPs in the mixture were significantly enhanced and could result in the disruption of the gill epithelium integrity. This study provides new insights into the combined effects of commonly used nanoparticles, emphasizing the importance of further investigating how their toxicity may be influenced in mixtures.

Microglial activation and pyroptosis induced by nano-TiO2 in marine medaka brain

Recently, nano-titanium dioxide (nano-TiO2) has been widely distributed over surface water. However, there are few reports on its effects on the central nervous system of fish. In this study, we investigated whether nano-TiO2 enters the medaka brain after exposure and its effect on the brain. Marine medaka brains were examined after exposure to 0.01 g/L nano-TiO2 for 3, 10, and 20 d. Nano-TiO2-like particles were found in the telencephalon of treated fish. There was no obvious brain histopathological injury. The number of irregular mitochondria with absent cristae increased. Gene expression of the apoptosis-related genes, casp8, bcl2b, and bax, decreased significantly in the nano-TiO2 group at 3 d. In contrast, the pyroptosis-related genes, gsdmeb and casp1, and inflammation-related factor, il18, increased significantly. As an activated microglia marker, mRNA expression of cd68 increased significantly in the nano-TiO2 treated group. Moreover, CD68 protein expression also increased significantly at 10 d. Altogether, we show that nano-TiO2 can alter mitochondrial morphology in the telencephalon of medaka, leading to microglial activation and pyroptosis.

Facilitating Seed Iron Uptake through Amine-Epoxide Microgels: A Novel Approach to Enhance Cucumber (Cucumis sativus) Germination

Enhancing the initial stages of plant growth by using polymeric gels for seed priming presents a significant challenge. This study aimed to investigate a microgel derived from polyetheramine-poly(propylene oxide) (PPO) and a bisepoxide (referred to as micro-PPO) as a promising alternative to optimize the seed germination process. The micro-PPO integrated with an iron micronutrient showed a positive impact on seed germination compared with control (Fe solutions) in which the root length yield improved up to 39%. Therefore, the element map by synchrotron-based X-ray fluorescence shows that the Fe intensities in the seed primers with the micro-PPO-Fe gel are about 3-fold higher than those in the control group, leading to a gradual distribution of Fe species through most internal embryo tissues. The use of micro-PPO for seed priming underscores their potential for industrial applications due to the nontoxicity results in zebrafish assays and environmentally friendly synthesis of the water-dispersible monomers employed.

Microplastics and TiO2 nanoparticles mixture as an emerging threat to amphibians: A case study on bullfrog embryos

Emerging contaminants can act as contributing factors to the decline of amphibian populations worldwide. Recently, scientists have drawn attention to the potential ecotoxicity of microplastics and nanomaterials in amphibians, however, their possible effects on embryonic developmental stages are still absent. Thus, the present study analyzed the developmental toxicity of environmentally relevant concentrations of polyethylene microplastics (PE MPs; 60 mg/L) and titanium dioxide nanoparticles (TiO2 NPs; 10 μg/L), isolated or in combination (Mix group) on bullfrog embryos, Aquarana catesbeiana, adapting the Frog Embryo Teratogenesis Assay (FETAX, 96h). Allied to the FETAX protocol, we also analyzed the heart rate and morphometric data. The exposure reduced the survival and hatching rates in groups exposed to TiO2 NPs, and to a lesser extent, also affected the Mix group. TiO2 NPs possibly interacted with the hatching enzymes of the embryos, preventing hatching, and reducing their survival. The reduced effects in the Mix group are due to the agglomeration of both toxicants, making the NPs less available for the embryos. PE MPs got attached to the gelatinous capsule of the chorion (confirmed by fluorescence microscopy), which protected the embryos from eventual direct effects of the microplastics on the hatching and survival rates. Although there were no cardiotoxic effects nor morphometric alterations, there was a significant increase in abdominal edemas in the hatched embryos of the PE MPs group, which indicates that osmoregulation might have been affected by the attachment of the microplastics on the embryos' gelatinous capsule. This study presents the first evidence of developmental toxicity of environmental mixtures of microplastics and nanoparticles on amphibians and reinforces the need for more studies with other amphibian species, especially neotropical specimens that could present bigger sensibility. Our study also highlighted several features of the FETAX protocol as useful tools to evaluate the embryotoxicity of several pollutants on amphibians.

Erythrocyte Recovery in Oreochromis niloticus Fish Exposed to Urban Effluents

Urban activities pollute aquatic ecosystems, and the integrity of organisms such as fish. The use of cytological techniques, such as the analysis of blood cellular integrity using the Micronucleus test, can help detect mutagenic damage as a result to urban effluents exposure. In this context, this study aimed to evaluate the frequency of micronucleus and other nuclear abnormalities in Oreochromis niloticus fish environmentally exposed to urban effluents in relation to their erythrocyte recovery capacity when exposed to clean water (30 and 45 days). The results indicated high copper, dissolved iron, nickel, and thermotolerant coliform levels in the urban stream. There was no difference in the frequency of micronuclei. In contrast, cells with nuclear nuclei, binucleates, kidney-shaped nuclei, notched nuclei, lobed nuclei, and segmented nuclei decreased according to the time the fish were exposed to clean water. When exposed to clean water, we conclude that urban fish recover from genotoxic and cytotoxic damage.

Novel data on genotoxic assessment of bismuth sulfide nanoflowers in common carp Cyprinus carpio

The environmental impacts and risks of nanomaterials that are commonly used in different technologies are of great concern as their toxic effects on the aquatic ecosystem remain unclear. In this study, bismuth sulfide (Bi2S3) nanoflowers (nfs) were synthesized using a microwave-based hydrothermal process, and their genotoxic effects were investigated in the common carp, Cyprinus carpio. Bi2S3 nanoflowers were applied to common carp for 96 h. LC50 value (LC50 = 350 mg/L-1) was determined for acute toxicity with probit analysis, and three sublethal concentrations (35, 87, and 175 mg/L-1) were selected accordingly for genotoxicity tests. Such LC50 value - 350 mg L-1 for the common carp makes these nanoflowers non-toxic to aquatic organisms according to the EU-Directive 93/67/EEC classification scheme. Toxicological evaluations of the sublethal concentrations of Bi2S3 nanoflowers demonstrated that the 35 and 87 mg L-1 Bi2S3nfs groups were generally harmless and similar to the control group. Only the 175 mg L-1 Bi2S3nfs group had significant DNA damage frequency and nuclear abnormalities than the control and other Bi2S3nfs groups. To the best of our knowledge, this is a novel data on genotoxicity reported for fish species exposed to Bi2S3 nanoflowers; however, further systematic studies need to be performed to fully estimate the effects of Bi2S3 nanoflowers on aquatic life.

Comparison of Toxicity of Nano and Bulk Titanium Dioxide on Nile Tilapia (Oreochromis niloticus): Acetylcholinesterase Activity Modulation and DNA Damage

This study compared effects of low concentrations (0.05 and 0.1 mg/L) of nano-TiO₂ and bulk-TiO₂ on brain, gill and liver acetylcholinesterase (AChE) and erythrocytic DNA of Nile tilapia over 7 and 14 days exposure. Both TiO₂ forms did not affect brain AChE activities. Bulk-TiO₂ induced elevation of gill AChE activities only after 7 days while nano-TiO₂ had no effect. Liver AChE activities were increased by 0.1 mg/L bulk- and nano-TiO₂ to similar extents. At 7 days, erythrocytic DNA damage was induced only by 0.1 mg/L nano- and bulk-TiO₂ to similar extents, but damage was not repaired to control levels at 7 days recovery period. At 14 days continuous exposure, DNA damage was induced by 0.05, 0.1 mg/L nano-TiO₂ and 0.1 mg/L of bulk-TiO₂ to similar extents. Results show that both forms of TiO₂ can pose genotoxic hazards to fish populations under sub-chronic exposure. However, their neurotoxic potential was not evident.