Genomic and chromosomal damage in the marine mussel Mytilus galloprovincialis: Effects of the combined exposure to titanium dioxide nanoparticles and cadmium chloride

Antagonistic effects of titanium dioxide nanoparticles on cadmium-induced nephrotoxicity and intestinal flora imbalance by reducing its bioavailability in rats

Titanium dioxide nanoparticles (nTiO2) possess unique physicochemical properties, such as large specific surface area, enabling heavy metals adsorption like Cadmium (Cd), yet the combined risks to the ecosystem and human remain unclear. This 90-day study explored the combined effects of nTiO2 (at a population-relevant dose of 100 mg/kg body weight administered via gavage) and cadmium chloride (CdCl2) (50 mg Cd/L by drinking water) on kidney and gut microbiota of rats. Co-exposure of nTiO2 and Cd significantly reduced the nephrotoxicity induced by Cd, with lower levels of urine biochemical indicators and Cd content, milder histopathological changes and ultrastructural damage. A two-way ANOVA analysis suggested antagonism between nTiO2 and Cd on urinary creatinine (CRE) and Urea. Coincidentally, gut microbiota remained unaffected by nTiO2 but was disrupted by Cd. Co-exposure also partially alleviated the adverse changes, restoring the decreased Beta-diversity and the relative abundance of bacteria to control levels. Furthermore, co-exposure resulted in a 19.2 % decline in the blood Cd concentration and an 8.6 % reduction in kidney, while the Cd content of 24 h feces was 3.6 % higher. These findings suggested antagonistic effects of nTiO2 against Cd-induced nephrotoxicity and intestinal flora disorder in rats. The effects might be attributed to the adsorption of nTiO2 on Cd, which resulted in the reduced Cd intake and distribution, coupled with increased excretion, thereby decreasing the Cd bioavailability. This study provides new evidence for understanding the impacts of nTiO2 and Cd on mammals and will contribute to the further risk assessments of co-exposure to human health and environment safety.

Extreme heat event influences the toxic impacts of nano-TiO2 with different crystal structures in mussel Mytilus coruscus

The wide use of nano‑titanium dioxide (nano-TiO2) and its ubiquitous emission into aquatic environments are threatening environmental health. Ambient temperature can affect the aggregation state of nano-TiO2 in seawater, thus influencing the intake and physiological effects on marine species. We studied the physiological effects of mixed nano-TiO2 (a mixture of anatase and rutile crystals with an average particle size of 25 nm, P25) on mussels. Subsequently, we investigated the oxidative stress, immunotoxicity, neurotoxicity, and detoxification in Mytilus coruscus exposed to two different crystal structures of nano-TiO2 (anatase and rutile) at 100 μg/L concentration under marine heatwaves (MHWs, 28 °C). MHWs and nano-TiO2 exposure induced neurotoxicity and immune damage and caused dysregulation of redox balance in the gills. Moreover, MHWs exposure disturbed the glutathione system and detoxification function of mussels, resulting in enhanced toxicity of nano-TiO2 under co-exposure. Anatase exposure significantly impaired the antioxidant system and downregulated the relative expression of antioxidant-related genes (Nrf2 and Bcl-2), HSP-90, and immune parameters under MHWs, while producing higher ROS levels compared to rutile. Based on integrated biomarker response (IBR), mussels co-exposed to anatase and MHW showed the highest value (19.29). However, there was no significant difference in bioaccumulation of titanium between anatase (6.07 ± 0.47 μg/g) and rutile (5.3 ± 0.44 μg/g) exposures under MHWs. These results indicate that MHWs would elevate the potential hazard of nanoparticles to marine organisms.

Aggravated visual toxicity in zebrafish larvae upon co-exposure to titanium dioxide nanoparticles and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate

The bioavailability and toxicity of organic pollutants in aquatic organisms can be largely affected by the co-existed nanoparticles. However, the impacts of such combined exposure on the visual system remain largely unknown. Here, we systematically investigated the visual toxicity in zebrafish larvae after single or joint exposure to titanium dioxide nanoparticles (n-TiO2) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) at environmentally relevant levels. Molecular dynamics simulations revealed the enhanced transmembrane capability of the complex than the individual, which accounted for the increased bioavailability of both TBPH and n-TiO2 when combined exposure to zebrafish. Transcriptome analysis showed that co-exposure to n-TiO2 and TBPH interfered with molecular pathways related to eye lens structure and sensory perception of zebrafish. Particularly, n-TiO2 or TBPH significantly suppressed the expression of βB1-crystallin and rhodopsin in zebrafish retina and lens, which was further enhanced after co-exposure. Moreover, we detected disorganized retinal histology, stunted lens development and significant visual behavioral changes of zebrafish under co-exposure condition. The overall results suggest that combined exposure to water borne n-TiO2 and TBPH increased their bioavailability, resulted in severer damage to optic nerve development and ultimately abnormal visual behavior patterns, highlighting the higher potential health risks of co-exposure to aquatic vertebrates.

Toxicity of Titanium Dioxide-Cerium Oxide Nanocomposites to Zebrafish Embryos: A Preliminary Evaluation

The widespread use of metal nanoparticles in different fields has raised many doubts regarding their possible toxicity to living organisms and the accumulation and discharge of metals in fish species. Among these nanoparticles, titanium dioxide (TiO2) and cerium oxide (CeO2) nanoparticles have mainly been employed in photocatalysis and water depuration. The aim of this research was to evaluate the potential toxic effects, after a co-exposure of TiO2-3%CeO2 nanoparticles, on zebrafish development, using an acute toxicity test. Increasing concentrations of TiO2-3%CeO2 nanoparticles were used (0.1-1-10-20 mg/L). The heartbeat rate was assessed using DanioscopeTM software (version 1.2) (Noldus, Leesburg, VA, USA), and the responses to two biomarkers of exposure (Heat shock proteins-70 and Metallothioneins) were evaluated through immunofluorescence. Our results showed that the co-exposure to TiO2-3%CeO2 nanoparticles did not affect the embryos' development compared to the control group; a significant difference (p < 0.05) at 48 hpf heartbeat for the 1, 10, and 20 mg/L groups was found compared to the unexposed group. A statistically significant response (p < 0.05) to Heat shock proteins-70 (Hsp70) was shown for the 0.1 and 1 mg/L groups, while no positivity was observed in all the exposed groups for Metallothioneins (MTs). These results suggest that TiO2-3%CeO2 nanocomposites do not induce developmental toxicity; instead, when considered separately, TiO2 and CeO2 NPs are harmful to zebrafish embryos, as previously shown.

Evaluation of Apical and Molecular Effects of Algae Pseudokirchneriella subcapitata to Cerium Oxide Nanoparticles

Cerium oxide engineered nanoparticles (nCeO₂) are widely used in various applications and are, also, increasingly being detected in different environmental matrixes. However, their impacts on the aquatic environment remain poorly quantified. Hence, there is a need to investigate their effects on non-target aquatic organisms. Here, we evaluated the cytotoxic and genotoxic effects of <25 nm uncoated-nCeO₂ on algae Pseudokirchneriella subcapitata. Apical (growth and chlorophyll a (Chl a) content) and genotoxic effects were investigated at 62.5-1000 µg/L after 72 and 168 h. Results demonstrated that nCeO₂ induced significant growth inhibition after 72 h and promotion post 96-168 h. Conversely, nCeO₂ induced enhanced Chl a content post 72 h, but no significant changes were observed between nCeO₂-exposed and control samples after 168 h. Hence, the results indicate P. subcapitata photosynthetic system recovery ability to nCeO₂ effects under chronic-exposure conditions. RAPD-PCR profiles showed the appearance and/or disappearance of normal bands relative to controls; indicative of DNA damage and/or DNA mutation. Unlike cell recovery observed post 96 h, DNA damage persisted over 168 h. Thus, sub-lethal nCeO₂-induced toxicological effects may pose a more serious threat to algae than at present anticipated.

The environmental remediation capacity of Ulva lactuca: the potential of macroalgae to reduce the threats caused by Titanium in marine invertebrate species

As a result of the wide use of Titanium (Ti) compounds in various products, Ti and Ti nanoparticles (nTi) are released into aquatic environments, inducing varying degrees of toxicity on aquatic fauna. Ulva lactuca, green macroalgae commonly found in coastal areas, has been extensively studied due to its worldwide distribution and capacity to accumulate trace elements under toxic conditions, which makes it a good universal sorbent. The present study aimed to establish the remediation properties of U. lactuca by evaluating the toxicity of Ti and nTi in bivalves, in the presence and absence of algae. Using the bivalve species Mytilus galloprovincialis, Ti toxicity was evaluated by assessing changes in mussel's metabolic capacity and oxidative status. Results evidenced cellular damage in M. galloprovincialis exposed to Ti and nTi. This was a result of the inactivation of antioxidant defences. The presence of U. lactuca limited cellular damage, however, this was not a result of the previously demonstrated bioremediation capacity, as no accumulation of Ti was verified in algal tissues. As a metabolic depression was verified for mussels exposed to Ti/nTi in the presence of algae, we hypothesise that U. lactuca may have been responsible for changes to the water quality which induced this response.

Nano-ecotoxicology in a changing ocean

The ocean faces an era of change, driven in large by the release of anthropogenic CO2, and the unprecedented entry of pollutants into the water column. Nanomaterials, those particles < 100 nm, represent an emerging contaminant of environmental concern. Research on the ecotoxicology and fate of nanomaterials in the natural environment has increased substantially in recent years. However, commonly such research does not consider the wider environmental changes that are occurring in the ocean, i.e., ocean warming and acidification, and occurrence of co-contaminants. In this review, the current literature available on the combined impacts of nanomaterial exposure and (i) ocean warming, (ii) ocean acidification, (iii) co-contaminant stress, upon marine biota is explored. Here, it is identified that largely co-stressors influence nanomaterial ecotoxicity by altering their fate and behaviour in the water column, thus altering their bioavailability to marine organisms. By acting in this way, such stressors, are able to mitigate or elevate toxic effects of nanomaterials in a material-specific manner. However, current evidence is limited to a relatively small set of test materials and model organisms. Indeed, data is biased towards effects upon marine bivalve species. In future, expanding studies to involve other ecologically significant taxonomic groups, primarily marine phytoplankton will be highly beneficial. Although limited in number, the available evidence highlights the importance of considering co-occurring environmental changes in ecotoxicological research, as it is likely in the natural environment, the material of interest will not be the sole stressor encountered by biota. As such, research examining ecotoxicology alongside co-occurring environmental stressors is essential to effectively evaluating risk and develop effective long-term management strategies.

Advances in genotoxicity of titanium dioxide nanoparticles in vivo and in vitro

Titanium dioxide nanoparticles (TiO₂ NPs) are currently one of the most widely used nanomaterials. Due to an increasing scope of applications, the exposure of humans to TiO₂ NP is inevitable, such as entering the body through the mouth with food additives or drugs, invading the damaged skin with cosmetics, and entering the body through the respiratory tract during the process of production and handling. Compared with TiO₂ coarse particles, TiO₂ NPs have stronger conductivity, reaction activity, photocatalysis, and permeability, which may lead to greater toxicity to organisms. Given that TiO₂ was classified as a category 2B carcinogen (possibly carcinogenic to humans), the genotoxicity of TiO₂ NPs has become the focus of attention. There have been a series of previous studies investigating the potential genotoxicity of TiO₂ NPs, but the existing research results are still controversial and difficult to conclude. More than half of studies have shown that TiO₂ NPs can cause genotoxicity, suggesting that TiO₂ NPs are likely to be genotoxic to humans. And the genotoxicity of TiO₂ NPs is closely related to the exposure concentration, mode and time, and experimental cells/animals as well as its physicochemical properties (crystal type, size, and shape). This review summarized the latest research progress of related genotoxic effects through in vivo studies and in vitro cell tests, hoping to provide ideas for the evaluation of TiO₂ NPs genotoxicity.

Combined toxicity of nano-TiO2 and Cd2+ to Scenedesmus obliquus: Effects at different concentration ratios

The continuous release of manufactured nanomaterials (MNMs) to environments raised concerns on their combined toxicological risks with co-existing contaminants, since MNMs might severely alter the environmental behavior and fate of the contaminants. In this study, the combined toxicity of nano-sized titanium dioxide (nTiO₂) and cadmium (Cd²⁺) to the green alga Scenedesmus obliquus and the underlying physicochemical mechanisms were investigated for the first time at different concentration ratios of Cd²⁺ to nTiO₂ to closely mimic the realistic environment scenarios where the concentration ratios of nTiO₂ to other contaminants are constantly changing. Our results suggested that under the co-exposure to different concentration ratios of Cd²⁺ to nTiO₂, the co-exposure contaminants exhibited three different combined toxicity modes (antagonistic, partially additive, and synergistic). Specifically, antagonistic combined toxicity was observed under co-exposure to a low concentration ratio of nTiO₂ to Cd²⁺ as the absorption by nTiO₂ decreased the bioavailability of Cd²⁺. However, the partially additive and synergistic combined toxicity occurred when the proportion of nTiO₂ in the co-exposure system was relatively high, which would mechanically and/or oxidatively damage the alga cell structures. Even worse, as a carrier of Cd²⁺, nTiO₂ enhanced the amount of Cd²⁺ entering cells, which significantly enhanced the toxicity of Cd²⁺ to algae. Overall, we demonstrated that concentration ratios of nTiO₂ to Cd²⁺ play an important role in determining the combined toxicity mode, which would provide a novel reference to environmental and health risk assessment of co-exposure to conventional pollutants and MNMs.

Eco-Interactions of Engineered Nanomaterials in the Marine Environment: Towards an Eco-Design Framework

Marine nano-ecotoxicology has emerged with the purpose to assess the environmental risks associated with engineered nanomaterials (ENMs) among contaminants of emerging concerns entering the marine environment. ENMs’ massive production and integration in everyday life applications, associated with their peculiar physical chemical features, including high biological reactivity, have imposed a pressing need to shed light on risk for humans and the environment. Environmental safety assessment, known as ecosafety, has thus become mandatory with the perspective to develop a more holistic exposure scenario and understand biological effects. Here, we review the current knowledge on behavior and impact of ENMs which end up in the marine environment. A focus on titanium dioxide (n-TiO₂) and silver nanoparticles (AgNPs), among metal-based ENMs massively used in commercial products, and polymeric NPs as polystyrene (PS), largely adopted as proxy for nanoplastics, is made. ENMs eco-interactions with chemical molecules including (bio)natural ones and anthropogenic pollutants, forming eco- and bio-coronas and link with their uptake and toxicity in marine organisms are discussed. An ecologically based design strategy (eco-design) is proposed to support the development of new ENMs, including those for environmental applications (e.g., nanoremediation), by balancing their effectiveness with no associated risk for marine organisms and humans.

Cytotoxicity and genotoxicity of coated-gold nanoparticles on freshwater algae Pseudokirchneriella subcapitata

Gold engineered nanoparticles (nAu) are increasingly detected in ecosystems, and this raises the need to establish their potential effects on aquatic organisms. Herein, cytotoxic and genotoxic effects of branched polyethylenimine (BPEI)- and citrate (cit)-coated nAu (5, 20, and 40 nm) on algae Pseudokirchneriella subcapitata were evaluated. The apical biological endpoints: growth inhibition and chlorophyll a (Chl a) content were investigated at 62.5-1000 µg/L over 168 h. In addition, the apurinic/apyrimidinic (AP) sites, randomly amplified polymorphic deoxyribonucleic acid (RAPD) profiles, and genomic template stability (GTS) were assessed to determine the genotoxic effects of nAu. The results show algal growth inhibition at 5 nm BPEI-nAu up to 96 h, and thereafter cell recovery except at the highest concentration of 1000 µg/L. Insignificant growth reduction for cit-nAu (all sizes), as well as 20 and 40 nm BPEI-nAu, was observed over 96 h, but growth promotion was apparent at all exposures thereafter except for 40 nm BPEI-nAu at 250 µg/L. A decrease in Chl a content following exposure to 5 nm BPEI-nAu at 1000 µg/L corresponded to significant algal growth reduction. In genotoxicity studies, a significant increase in AP sites content was observed relative to the control - an indication of nAu ability to induce genotoxic effects irrespective of their size and coating type. For 5 nm- and 20 nm-sized nAu for both coating types and exposure concentrations no differences in AP sites content were observed after 72 and 168 h. However, a significant reduction in AP sites was observed following algae exposure to 40 nm-sized nAu (irrespective of coating type and exposure concentration) at 168 h compared to 72 h. Thus, AP sites results at 40 nm-size suggest likely DNA damage recovery over a longer exposure period. The findings on AP sites content showed a good correlation with an increase in genome template stability and growth promotion observed after 168 h. In addition, RAPD profiles demonstrated that nAu can induce DNA damage and/or DNA mutation to P. subcapitata as evidenced by the appearance and/or disappearance of normal bands compared to the controls. Therefore, genotoxicity results revealed significant toxicity of nAu to algae at the molecular level although no apparent effects were detectable at the morphological level. Overall, findings herein indicate that long-term exposure of P. subcapitata to low concentrations of nAu may cause undesirable sub-lethal ecological effects.

Toxic effects of nano-TiO2 in bivalves-A synthesis of meta-analysis and bibliometric analysis

Since the beginning of the 21st century, the increasing production and application of nano-TiO₂ in consumer products have inevitably led to its release into aquatic systems and therefore caused the exposure of aquatic organisms, resulting in growing environmental concerns. However, the safety of nano-TiO₂ in aquatic environments has not been systematically assessed, especially in coastal and estuary waters where a large number of filter-feeding animals live. Bivalves are considered around the world to be a unique target group for nanoparticle toxicity, and numerous studies have been conducted to test the toxic effects of nano-TiO₂ on bivalves. The aim of this review was to systematically summarize and analyze published data concerning the toxicological effects of nano-TiO₂ in bivalves. In particular, the toxicity of nano-TiO₂ to the antioxidant system and cell physiology was subjected to meta-analysis to reveal the mechanism of the toxicological effects of nano-TiO₂ and the factors affecting its toxicological effects. To reveal the cooperation, hot keywords and co-citations in this field, bibliometric analysis was conducted, and the results showed that the toxicological molecular mechanisms of nano-TiO₂ and the combined effects of nano-TiO₂ and other environmental factors are two major hot spots. Finally, some perspectives and insights were provided in this review for future research on nano-TiO₂ toxicology in bivalves.

Suitability of Nanoparticles to Face Benzo(a)pyrene-Induced Genetic and Chromosomal Damage in M. galloprovincialis. An In Vitro Approach

Benzo(a)pyrene (B(a)P) is a well-known genotoxic agent, the removal of which from environmental matrices is mandatory, necessitating the application of cleaning strategies that are harmless to human and environmental health. The potential application of nanoparticles (NPs) in the remediation of polluted environments is of increasing interest. Here, specifically designed NPs were selected as being non-genotoxic and able to interact with B(a)P, in order to address the genetic and chromosomal damage it produces. A newly formulated pure anatase nano-titanium (nano-TiO2), a commercial mixture of rutile and anatase, and carbon black-derived hydrophilic NPs (HNP) were applied. Once it had been ascertained that the NPs selected for the work did not induce genotoxicity, marine mussel gill biopsies were exposed in vitro to B(a)P (2 μg/mL), alone and in combination with the selected NPs (50 µg/mL nano-TiO2, 10 µg/mL HNP). DNA primary reversible damage was evaluated by means of the Comet assay. Chromosomal persistent damage was assessed on the basis of micronuclei frequency and nuclear abnormalities by means of the Micronucleus-Cytome assay. Transmission Electron Microscopy (TEM) was performed to investigate the mechanism of action exerted by NPs. Pure Anatase n-TiO2 was found to be the most suitable for our purpose, as it is cyto- and genotoxicity free and able to reduce the genetic and chromosomal damage associated with exposure to B(a)P.

Adsorption of Cd to TiO2-NPs Forms Low Genotoxic AGGREGATES in Zebrafish Cells

The aquatic environment is involved in the pollutants spreading mechanisms, including nanomaterials and heavy metals. The aims of this study were to assess the in vivo genotoxicity of Cd (1 mg/L) and to investigate the genomic effects generated by its co-exposure with TiO₂-NPs (10 µg/L). The study was performed using zebrafish as a model for 5, 7, 14, 21, and 28 days of exposure. The genotoxic potential was assessed by three experimental approaches: DNA integrity, degree of apoptosis, and molecular alterations at the genomic level by genomic template stability (% GTS) calculation. Results showed an increased in DNA damage after Cd exposure with a decrease in % GTS. The co-exposure (TiO₂-NPs + Cd) induced a no statistically significant loss of DNA integrity, a reduction of the apoptotic cell percentage and the recovery of genome stability for prolonged exposure days. Characterization and analytical determinations data showed Cd adsorption to TiO₂-NPs, which reduced free TiO₂-NPs levels. The results of our study suggest that TiO₂-NPs could be used for the development of controlled heavy metal bioremediation systems.

Status Quo in Data Availability and Predictive Models of Nano-Mixture Toxicity

Co-exposure of nanomaterials and chemicals can cause mixture toxicity effects to living organisms. Predictive models might help to reduce the intensive laboratory experiments required for determining the toxicity of the mixtures. Previously, concentration addition (CA), independent action (IA), and quantitative structure–activity relationship (QSAR)-based models were successfully applied to mixtures of organic chemicals. However, there were few studies concerning predictive models for toxicity of nano-mixtures before June 2020. Previous reviews provided comprehensive knowledge of computational models and mechanisms for chemical mixture toxicity. There is a gap in the reviewing of datasets and predictive models, which might cause obstacles in the toxicity assessment of nano-mixtures by using in silico approach. In this review, we collected 183 studies of nano-mixture toxicity and curated data to investigate the current data and model availability and gap and to derive research challenges to facilitate further experimental studies for data gap filling and the development of predictive models.

Cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to PVP/PEI coated Ag nanoparticles at two seasons

Silver nanoparticles (Ag NPs) are present in numerous consumer products due to their antimicrobial and other unique properties, thus concerns about their potential input into aquatic ecosystems are increasing. Toxicity of Ag NPs in waterborne exposed aquatic organisms has been widely investigated, but studies assessing the potential toxic effects caused after ingestion through the food web, especially at low realistic concentrations, remain scarce. Moreover, it is not well known whether season may influence toxic effects of Ag NPs. The main objective of this study was to determine cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to poly-N-vinyl-2-pirrolidone/polyethyleneimine (PVP/PEI) coated 5 nm Ag NPs for 1, 7 and 21 days both in autumn and spring. Mussels were fed every day with microalgae Isochrysis galbana exposed for 24 h to a low dose (1 μg Ag/L Ag NPs) in spring and to a higher dose (10 μg Ag/L Ag NPs) in spring and autumn. Mussels fed with microalgae exposed to the high dose accumulated Ag significantly after 21 days in both seasons, higher levels being measured in autumn compared to spring. Intralysosomal metal accumulation measured in mussel digestive gland and time- and dose-dependent reduction of mussels health status was similar in both seasons. DNA strand breaks increased significantly in hemocytes at both exposure doses along the 21 days in spring and micronuclei frequency showed an increasing trend after 1 and 7 days of exposure to 1 μg Ag/L Ag NPs in spring and to 10 μg Ag/L in both seasons. Values decreased after 21 days of exposure in all the cases. In conclusion, PVP/PEI coated 5 nm Ag NPs ingested through the food web were significantly accumulated in mussel tissues and caused adverse cell and tissue level effects both in autumn and in spring.

Rethinking Nano-TiO2 Safety: Overview of Toxic Effects in Humans and Aquatic Animals

Titanium dioxide nanoparticles (nano-TiO₂ ) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano-TiO₂ on human and environmental health is provided. A meta-analysis is conducted to analyze the toxicity of nano-TiO₂ to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano-TiO₂ , aquatic environments that receive high nano-TiO₂ inputs are focused on, and the toxicity of nano-TiO₂ to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano-TiO₂ toxicity. Furthermore, nano-TiO₂ can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano-TiO₂ toxicity is manifested as the negative effects on fitness-related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano-TiO₂ and the combined effects of nano-TiO₂ and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano-TiO₂ on humans and non-target organisms has emerged as an underexplored topic requiring further investigation.

Environmental transformation of n-TiO2 in the aquatic systems and their ecotoxicity in bivalve mollusks: A systematic review

Over the past decades, titanium dioxide nanoparticles (n-TiO₂) have been extensively used in several industrial applications and the manufacture of novel consumer products. Although strict regulations have been put in place to limit their release into the aquatic environment, these nanoparticles can still be found at elevated levels within the environment, which can result in toxic effects on exposed organisms and has possible implications in term of public health. Bivalve mollusks are a unique and ideal group of shellfish for the study and monitoring the aquatic pollution by n-TiO₂ because of their filter-feeding behaviour and ability to accumulate toxicants in their tissues. In these animals, exposure to n-TiO₂ leads to oxidative stress, immunotoxicity, neurotoxicity, and genotoxicity, as well as behavioral and physiological changes. This review summarizes the uptake, accumulation, and fate of n-TiO₂ in aquatic environments and the possible interactions between n-TiO₂ and other contaminants such as heavy metals and organic pollutants. Moreover, the toxicological impacts and mechanisms of action are discussed for a wide range of bivalve mollusks. This data underlines the pressing need for additional knowledge and future research plans for the development of control strategies to mitigate the release of n-TiO₂ to the aquatic environment to prevent the toxicological impacts on bivalves and protect public health.

Effect-Based Approach to Assess Nanostructured Cellulose Sponge Removal Efficacy of Zinc Ions from Seawater to Prevent Ecological Risks

To encourage the applicability of nano-adsorbent materials for heavy metal ion removal from seawater and limit any potential side effects for marine organisms, an ecotoxicological evaluation based on a biological effect-based approach is presented. ZnCl2 (10 mg L-1) contaminated artificial seawater (ASW) was treated with newly developed eco-friendly cellulose-based nanosponges (CNS) (1.25 g L-1 for 2 h), and the cellular and tissue responses of marine mussel Mytilus galloprovincialis were measured before and after CNS treatment. A control group (ASW only) and a negative control group (CNS in ASW) were also tested. Methods: A significant recovery of Zn-induced damages in circulating immune and gill cells and mantle edges was observed in mussels exposed after CNS treatment. Genetic and chromosomal damages reversed to control levels in mussels' gill cells (DNA integrity level, nuclear abnormalities and apoptotic cells) and hemocytes (micronuclei), in which a recovery of lysosomal membrane stability (LMS) was also observed. Damage to syphons, loss of cilia by mantle edge epithelial cells and an increase in mucous cells in ZnCl2-exposed mussels were absent in specimens after CNS treatment, in which the mantle histology resembled that of the controls. No effects were observed in mussels exposed to CNS alone. As further proof of CNS' ability to remove Zn(II) from ASW, a significant reduction of >90% of Zn levels in ASW after CNS treatment was observed (from 6.006 to 0.510 mg L-1). Ecotoxicological evaluation confirmed the ability of CNS to remove Zn from ASW by showing a full recovery of Zn-induced toxicological responses to the levels of mussels exposed to ASW only (controls). An effect-based approach was thus proven to be useful in order to further support the environmentally safe (ecosafety) application of CNS for heavy metal removal from seawater.

In Vitro Effects of Titanium Dioxide Nanoparticles (TiO2NPs) on Cadmium Chloride (CdCl2) Genotoxicity in Human Sperm Cells

The environmental release of titanium dioxide nanoparticles (TiO₂NPs) associated with their intensive use has been reported to have a genotoxic effect on male fertility. TiO₂NP is able to bind and transport environmental pollutants, such as cadmium (Cd), modifying their availability and/or toxicity. The aim of this work is to assess the in vitro effect of TiO₂NPs and cadmium interaction in human sperm cells. Semen parameters, apoptotic cells, sperm DNA fragmentation, genomic stability and oxidative stress were investigated after sperm incubation in cadmium alone and in combination with TiO₂NPs at different times (15, 30, 45 and 90 min). Our results showed that cadmium reduced sperm DNA integrity, and increased sperm DNA fragmentation and oxidative stress. The genotoxicity induced by TiO₂NPs-cadmium co-exposure was lower compared to single cadmium exposure, suggesting an interaction of the substances to modulate their reactivity. The Quantitative Structure-Activity Relationship (QSAR) computational method showed that the interaction between TiO₂NPs and cadmium leads to the formation of a sandwich-like structure, with cadmium in the middle, which results in the inhibition of its genotoxicity by TiO₂NPs in human sperm cells.

Genetic impacts induced by BaP and Pb in Mytilus coruscus: Can RAPD be a validated tool in genotoxicity evaluation both in vivo and in vitro?

Benzo(α)pyrene (BaP) and lead (Pb) are common pollutants discharged greatly in ocean and causing detrimental impacts on marine organisms. Although mussels are one of the most prominent and frequently studied biological models, the research on their genomic alterations induced by the mixture of two totally different chemicals, is still rare. In present study, local marine mussels Mytilus coruscus were exposed in vivo to BaP (53.74 ± 19.79 μg/L), Pb (2.58 ± 0.11 mg/L) and their mixture for 6 days. The genotoxic damages were assessed by comet assay, micronucleus (MNi) test, and random amplified polymorphic DNA (RAPD) analysis. Significantly increased though transitory genomic damage was investigated after the exposure and showed consistency using various detecting methods. Additive genotoxicity was only found after 3 days combined exposure by means of MNi test, suggesting that BaP and Pb may play with alternative biological targets during metabolism and/or interaction with the genome. The geno-stability and the recovery capability were further detected both in vivo and in vitro after challenged by BaP. RAPD results showed coherence in BaP induced genotoxicity, together with time-specific alterations. The genomic instability was found to recover in both in vivo and in vitro exposure scenarios in present study. To our knowledge, this is the first study to focus on the genotoxicitiy induced by BaP, Pb and their mixture by multiple detecting techniques. The attempt to utilize model pollutants and marine organism to validate the potential value of RAPD analysis highlighted that it might be a useful tool in the research of genotoxicology, especially on the effect-mechanism interplay at genetic level.

In vitro genotoxic effects of titanium dioxide nanoparticles (n-TiO2 ) in human sperm cells

Titanium dioxide nanoparticles (TiO₂ -NPs) are one of the most widely engineered nanoparticles used. The study has been focused on TiO ₂ -NPs genotoxic effects on human spermatozoa in vitro. TiO ₂ -NPs are able to cross the blood-testis barrier induced inflammation, cytotoxicity, and gene expression changes that lead to impairment of the male reproductive system. This study presents new data about DNA damage in human sperms exposed in vitro to two n-TiO ₂ concentrations (1 µg/L and 10 µg/L) for different times and the putative role of reactive oxygen species (ROS) as mediators of n-TiO ₂ genotoxicity. Primary n-TiO ₂ characterization was performed by transmission electron microscopy. The dispersed state of the n-TiO ₂ in media was spectrophotometrically determined at 0, 24, 48, and 72 hr from the initial exposure. The genotoxicity has been highlighted by different experimental approaches (comet assay, terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL] test, DCF assay, random amplification of polymorphic DNA polymerase chain reaction [RAPD-PCR]). The comet assay showed a statistically significant loss of sperm DNA integrity after 30 min of exposure. Increased threshold of sperm DNA fragmentation was highlighted after 30 min of exposure by the TUNEL Test. Also, the RAPD-PCR analysis showed a variation in the polymorphic profiles of the sperm DNA exposed to n-TiO ₂ . The evidence from the DCF assay showed a statistically significant increase in intracellular ROS linked to n-TiO ₂ exposure. This research provides the evaluation of n-TiO ₂ potential genotoxicity on human sperm that probably occurs through the production of intracellular ROS.

The Comet Assay in Marine Animals

Comet assay is a quick and versatile technique for assessing DNA damage in individual cells. It allows for the detection of DNA single- and double-strand breaks, as well as the presence of alkali labile sites and cross-links. Here we describe protocols for the single-cell gel electrophoresis (Comet assay) in its alkaline (pH > 13), mild alkaline (pH = 12.1) and neutral (pH = 8) versions when applied in marine animals.

Environmental mixtures of nanomaterials and chemicals: The Trojan-horse phenomenon and its relevance for ecotoxicity

The usage of engineered nanomaterials (NM) offers many novel products and applications with advanced features, but at the same time raises concerns with regard to potential adverse biological effects. Upon release and emission, NM may interact with chemicals in the environment, potentially leading to a co-exposure of organisms and the occurrence of mixture effects. A prominent idea is that NM may act as carriers of chemicals, facilitating and enhancing the entry of substances into cells or organisms, subsequently leading to an increased toxicity. In the literature, the term 'Trojan-horse effect' describes this hypothesis. The relevance of this mechanism for organisms is, however, unclear as yet. Here, a review has been performed to provide a more systematic picture on existing evidence. It includes 151 experimental studies investigating the exposure of various NM and chemical mixtures in ecotoxicological in vitro and in vivo model systems. The papers retrieved comprised studies investigating (i) uptake, (ii) toxicity and (iii) investigations considering both, changes in substance uptake and toxicity upon joint exposure of a chemical with an NM. A closer inspection of the studies demonstrated that the existing evidence for interference of NM-chemical mixture exposure with uptake and toxicity points into different directions compared to the original Trojan-horse hypothesis. We could discriminate at least 7 different categories to capture the evidence ranging from no changes in uptake and toxicity to an increase in uptake and toxicity upon mixture exposure. Concluding recommendations for the consideration of relevant processes are given, including a proposal for a nomenclature to describe NM-chemical mixture interactions in consistent terms.

Dioxin-like compounds bioavailability and genotoxicity assessment in the Gulf of Follonica, Tuscany (Northern Tyrrhenian Sea)

The Gulf of Follonica (Italy) is impacted by the chemical pollution from ancient mining activity and present industrial processes. This study was aimed to determine the bioavailability of dioxin-like compounds (DLCs) in coastal marine environment and to assess the genotoxic potential of waste waters entering the sea from an industrial canal. Moderately high levels of DCLs compounds (∑ PCDDs + PCDFs 2.18–29.00 pg/g dry wt) were detected in Mytilus galloprovincialis transplanted near the waste waters canal and their corresponding Toxic Equivalents (TEQs) calculated. In situ exposed mussels did not show any genotoxic effect (by Comet and Micronucleus assay). Otherwise, laboratory exposure to canal waters exhibited a reduced genomic template stability (by RAPD-PCR assay) but not DNA or chromosomal damage. Our data reveal the need to focus on the levels and distribution of DLCs in edible species from the study area considering their potential transfer to humans through the consumption of sea food.

Plasma lead, silicon and titanium concentrations are considerably higher in green sea turtle from the suburban coast than in those from the rural coast in Okinawa, Japan

The purpose of this study was to compare the concentration of trace elements in the plasma of sea turtles that inhabited the suburban (Okinawa Main Island, n=8) and the rural coast (Yaeyama Island, n=57) in Okinawa, Japan. Particle induced X-ray emission allowed detection of 20 trace and major elements. The wild sea turtles in the suburban coast in Okinawa were found to have high concentrations of Pb, Si and Ti in the plasma when compared to the rural area but there were no significant changes in the Al, As and Hg concentrations. These results may help to suggest the status of some elements in a marine environment. Further, monitoring the plasma trace and major element status in sea turtles can be used as a bio-monitoring approach by which specific types of elements found here could indicate effects that are related to human activities.

Ecophysiological perspectives on engineered nanomaterial toxicity in fish and crustaceans

Engineered nanomaterials (ENMs) are incorporated into numerous industrial, clinical, food, and consumer products and a significant body of evidence is now available on their toxicity to aquatic organisms. Environmental ENM concentrations are difficult to quantify, but production and release estimates suggest wastewater treatment plant effluent levels ranging from 10^-4 to >10¹μgL^-1 for the most common formulations by production volume. Bioavailability and ENM toxicity are heavily influenced by water quality parameters and the physicochemical properties and resulting colloidal behaviour of the particular ENM formulation. ENMs generally induce only mild acute toxicity to most adult fish and crustaceans under environmentally relevant exposure scenarios; however, sensitivity may be considerably higher for certain species and life stages. In adult animals, aquatic ENM exposure often irritates respiratory and digestive epithelia and causes oxidative stress, which can be associated with cardiovascular dysfunction and the activation of immune responses. Direct interactions between ENMs (or their dissolution products) and proteins can also lead to ionoregulatory stress and/or developmental toxicity. Chronic and developmental toxicity have been noted for several common ENMs (e.g. TiO₂, Ag), however more data is necessary to accurately characterize long term ecological risks. The bioavailability of ENMs should be limited in saline waters but toxicity has been observed in marine animals, highlighting a need for more study on possible impacts in estuarine and coastal systems. Nano-enabled advancements in industrial processes like water treatment and remediation could provide significant net benefits to the environment and will likely temper the relatively modest impacts of incidental ENM release and exposure.

Efficient and safe gene transfection in fish spermatogonial stem cells using nanomaterials

The nanomaterials MWCNTs, NGO and NRs can be functionalized and complexed to DNA to promote efficient gene delivery to Nile tilapia spermatogonial stem cells inducing less cell death than electroporation and the commercial reagents tested.