Assessment of silver nanoparticle toxicity for common carp (Cyprinus carpio) fish embryos using a novel method controlling the agglomeration in the aquatic media

Effects of plastic particles on aquatic invertebrates and fish - A review

This review summarises the current knowledge on the effects of microplastics and their additives on organisms living in the aquatic environment, particularly invertebrates and fish. To date, microplastics have been recognised to affect not only the behaviour of aquatic animals but also their proper development, causing variations in fertility, oxidative stress, inflammations and immunotoxicity, neurotoxicity, and changes in metabolic pathways and gene expression. The ability of microplastics to bind other xenobiotics and cause combined toxicity along side the effect of other agents is also discussed as well. Microplastics are highly recalcitrant materials in both freshwater and marine environments and should be considered extremely toxic to aquatic ecosystems. They are severely problematic from ecological, economic and toxicological standpoints.

Evaluating the Use of TiO2 Nanoparticles for Toxicity Testing in Pulmonary A549 Cells

Purpose

Titanium dioxide nanoparticles, 25 nm in size of crystallites (TiO₂ P25), are among the most produced nanomaterials worldwide. The broad use of TiO₂ P25 in material science has implied a request to evaluate their biological effects, especially in the lungs. Hence, the pulmonary A549 cell line has been used to estimate the effects of TiO₂ P25. However, the reports have provided dissimilar results on caused toxicity. Surprisingly, the physicochemical factors influencing TiO₂ P25 action in biological models have not been evaluated in most reports. Thus, the objective of the present study is to characterize the preparation of TiO₂ P25 for biological testing in A549 cells and to evaluate their biological effects.

Methods

We determined the size and crystallinity of TiO₂ P25. We used four techniques for TiO₂ P25 dispersion. We estimated the colloid stability of TiO₂ P25 in distilled water, isotonic NaCl solution, and cell culture medium. We applied the optimal dispersion conditions for testing the biological effects of TiO₂ P25 (0–100 µg.mL⁻¹) in A549 cells using biochemical assays (dehydrogenase activity, glutathione levels) and microscopy.

Results

We found that the use of fetal bovine serum in culture medium is essential to maintain sufficient colloid stability of dispersed TiO₂ P25. Under these conditions, TiO₂ P25 were unable to induce a significant impairment of A549 cells according to the results of biochemical and microscopy evaluations. When the defined parameters for the use of TiO₂ P25 in A549 cells were met, similar results on the biological effects of TiO₂ P25 were obtained in two independent cell laboratories.

Conclusion

We optimized the experimental conditions of TiO₂ P25 preparation for toxicity testing in A549 cells. The results presented here on TiO₂ P25-induced cellular effects are reproducible. Therefore, our results can be helpful for other researchers using TiO₂ P25 as a reference material.

Post hatching stages of tropical catfish Rhamdia quelen (Quoy and Gaimard, 1824) are affected by combined toxic metals exposure with risk to population

Toxic metals and silver nanoparticles (AgNPs) are of great importance as pollutants and their frequent use increases the risk of exposure to biota, but few studies have described co-toxic effects in aquatic organisms. In fish, the method using early stages of development are interesting parameters to validate ecotoxicological studies, and more recently, the use of mathematical models has substantially increased the efficiency of the method. Post hatching stages of native catfish Rhamdia quelen were exposed to single or combined mixtures of toxic metals (Mn, Pb, Hg or AgNPs) in order to study its effects. Fertilized eggs were exposed for 24, 48, 72, and 96 h, where hatching and survival rates, malformation frequency, and neuromast structure damages were evaluated. The results showed alterations in hatching rate after single and combined exposure to metals, but mixtures showed effects more severe comparatively with the single exposures. A similar result including a time-dependent effect was observed in survival rates and incidence of deformities. Overall, embryos and larvae were sensitive to toxic metals exposure while the mathematical modeling suggested a population reduction size including risk of local extinction.

Cytotoxicity, Accumulation and Translocation of Silver and Silver Sulfide Nanoparticles in contact with Rainbow Trout Intestinal Cells

Silver nanoparticles (Ag NPs) are widely used in consumer products especially because of their antimicrobial properties. However, this wide usage of Ag NPs is accompanied by their release into the environment where they will be rapidly transformed to other silver species - especially silver sulfide (Ag₂S). In the present study, we synthesized Ag NPs and sulfidized them to obtain a core-shell system Ag@Ag₂S NPs. Both types of particles form stable dispersions with hydrodynamic diameters of less than 100 nm when diluted in water, but tend to form micrometer-sized agglomerates in biological exposure media. Application of Ag and Ag@Ag₂S NPs to rainbow trout intestinal cells (RTgutGC) resulted in a concentration-dependent cytotoxicity for both types of particles, as assessed by a three-endpoint assay for metabolic activity, membrane integrity and lysosomal integrity. The Ag NPs were shown to be slightly more toxic than the Ag@Ag₂S NPs. Adding Ag or Ag@Ag₂S NPs to RTgutGC cells, grown on a permeable membrane to mimic the intestinal barrier, revealed considerable accumulation of silver for both types of particles. Indeed, the cells significantly attenuated the NP translocation, allowing only a fraction of the metal to translocate across the intestinal epithelium. These findings support the notion that the intestine constitutes an important sink for Ag NPs and that, despite the reduced cytotoxicity of a sulfidized NP form, the particles can enter fish where they may constitute a long-term source for silver ion release and cytotoxicity.

Assessment of aqueous phase ozonation on aggregation of polyvinylpyrrolidone-capped silver nanoparticles

Due to the antibacterial characteristics, numerous-growing applications of silver nanoparticles (AgNPs) and its coated forms impact water treatment by ozone. The influence of ozone on the aggregation of bare AgNPs and polyvinylpyrrolidone-capped form (PVP-AgNPs) was investigated, as toxicity of NPs depends on particle aggregation/surface charge. Full factorial experimental design was employed to investigate the impact of pH, concentration of NPs' suspension, and ozonation time on bare and PVP-capped AgNPs. Z-Average, zeta potential, and polydispersity index (PdI) of NPs were measured as aggregation criteria. The most effective variables on aggregation of NPs were the coating layer (40-75.5% contribution), pH (14.1-29.6% contribution), and ozonation time (6.5-10.1% contribution), respectively. The aggregation rate increased with increasing ozonation time and decreased with pH. The aggregation of ozonated AgNPs (Z-average up to ~ 4000 nm) was much greater than that of ozonated PVP-AgNPs (Z-average up to ~ 450 nm) due to interaction of ozone-PVP stabilizing layer. During ozonation, the PVP-AgNPs' surface charge shifted from - 6.62 (steric repulsion) to - 29.17 mV (electrosteric repulsion) at pH 7.5, thereby requiring more treatment time to aggregate compared with AgNPs. Graphical abstract.

Study of zinc oxide nanoparticles and zinc chloride toxicity to annelid Enchytraeus crypticus in modified agar-based media

Acute toxicity of zinc oxide nanoparticle (ZnO-NP, mean particle size diameter of 10 nm) powder and water-soluble salt of zinc (ZnCl₂) to annelid Enchytraeus crypticus was tested using an agar-based nutrient-enriched medium with the addition of kaolin and humic acids (HA). Adults of the E. crypticus were cultivated in pure agar and in three types of modified exposure media containing different proportions of model soil constituents. Potworms were exposed to zinc in both forms (1-1000 mg kg^-1 of agar) for 96 h. In experiments with ZnCl₂, toxicity of zinc was the highest in pure agar followed by agar with HA and agar with kaolin and HA and the lowest toxicity was observed in agar with kaolin. The corresponding LC₅₀ values were 13.2, 28.8, 39.4, and 75.4 mg kg^-1 respectively. In contrast, zinc in the form of ZnO-NPs was most toxic in the presence of HA followed by pure agar, agar with kaolin, and kaolin with HA. In this case, LC₅₀ values were 15.8, 43.5, 111, and 122 mg kg^-1 respectively. Scanning electron microscopy revealed that the smallest agglomerates occurred in the presence of kaolin, where ZnO-NPs were sealed in a kaolin shell. This effect reduced the bioavailability and toxicity of the NPs. In contrast, larger agglomerates were observed in the presence of HA but a larger amount of zinc was dispersed in the volume of agar.

Toxicology of Engineered Nanoparticles: Focus on Poly(amidoamine) Dendrimers

Engineered nanomaterials are increasingly being developed for paints, sunscreens, cosmetics, industrial lubricants, tyres, semiconductor devices, and also for biomedical applications such as in diagnostics, therapeutics, and contrast agents. As a result, nanomaterials are being manufactured, transported, and used in larger and larger quantities, and potential impacts on environmental and human health have been raised. Poly(amidoamine) (PAMAM) dendrimers are specifically suitable for biomedical applications. They are well-defined nanoscale molecules which contain a 2-carbon ethylenediamine core and primary amine groups at the surface. The systematically variable structural architecture and the large internal free volume make these dendrimers an attractive option for drug delivery and other biomedical applications. Due to the wide range of applications, the Organisation for Economic Co-Operation and Development (OECD) have included them in their list of nanoparticles which require toxicological assessment. Thus, the toxicological impact of these PAMAM dendrimers on human health and the environment is a matter of concern. In this review, the potential toxicological impact of PAMAM dendrimers on human health and environment is assessed, highlighting work to date exploring the toxicological effects of PAMAM dendrimers.

Comparative toxicities of silver nitrate, silver nanocolloids, and silver chloro-complexes to Japanese medaka embryos, and later effects on population growth rate

Fish embryo toxicology is important because embryos are more susceptible than adults to toxicants. In addition, the aquatic toxicity of chemicals depends on water quality. We examined the toxicities to medaka embryos of three types of silver-AgNO₃, silver nanocolloids (SNCs), and silver ions from silver nanoparticle plates (SNPPs)-under three pH conditions (4.0, 7.0, and 9.0) in embryo-rearing medium (ERM) or ultrapure water. Furthermore, we tested the later-life-stage effects of SNCs on medaka and their population growth. "Later-life-stage effects" were defined here as delayed toxic effects that occurred during the adult stage of organisms that had been exposed to toxicant during their early life stage only. AgNO₃, SNCs, and silver ions were less toxic in ERM than in ultrapure water. Release of silver ions from the SNPPs was pH dependent: in ERM, silver toxicity was decreased owing to the formation of silver chloro-complexes. SNC toxicity was higher at pH 4.0 than at 7.0 or 9.0. AgNO₃ was more toxic than SNCs. To observe later-life effects of SNCs, larvae hatched from embryos exposed to 0.01 mg/L SNCs in ultrapure water were incubated to maturity under clean conditions. The mature medaka were then allowed to reproduce for 21 days. Calculations using survival ratios and reproduction data indicated that the intrinsic population growth rate decreased after exposure of embryos to SNC. SNC exposure reduced the extinction time as a function of the medaka population-carrying capacity.

How the tapeworm Hymenolepis diminuta affects zinc and cadmium accumulation in a host fed a hyperaccumulating plant (Arabidopsis halleri)

The effects of plant-bound zinc (Zn) and cadmium (Cd) on element uptake and their interactions in a parasite-host system were investigated in a model experiment. Male Wistar rats were divided into four groups (C, P, TC and TP). Groups TC and TP were infected with the rat tapeworm Hymenolepis diminuta. Groups C and TC were fed a standard rodent mixture (ST-1) and received 10.5 mg of Zn per week, while groups P and TP were fed a mixture supplemented with the Zn- and Cd-hyperaccumulating plant Arabidopsis halleri at a dosage of 236 mg Zn/week and 3.0 mg Cd/week. Rats were euthanized after 6 weeks, and Cd and Zn levels were determined in rat and tapeworm tissue. The results indicate that tapeworm presence did have an effect on Cd and Zn concentrations in the host tissue; the majority of tissues in infected rats had statistically significant lower Zn and Cd concentrations than did uninfected rats. Tapeworms accumulated more zinc and cadmium than did the majority of host tissues. This important finding confirms the ability of tapeworms to accumulate certain elements (heavy metals) from the host body to their own body tissues. Thus, tapeworms can decrease heavy metal concentrations in host tissues.