Currents, wave motion, solar radiation, and abrasion are mechanisms responsible for the degradation of large plastic artifacts and contribute to the dispersion of micro and nanoplastics into aquatic ecosystems, which are, currently, the most dangerous threats due to their invisibility and persistence. The present work evaluated the possible lethal and sublethal effects of amino-modified polystyrene nanoplastics (nPS-NH₂) with diameters of 50 nm and 100 nm on Artemia salina (A. salina), an organism at the base of the trophic chain of the aquatic system, using a widely used model for the analysis of embryotoxicity from environmental pollutants. For this purpose, after evaluating the biodistribution of nanoplastics in the body of the tested animals, several endpoints such as anomalies, apoptosis, and ROS production were assessed. In addition, particular attention was dedicated to evaluating the correlation between toxicity and the particle size tested. The results reported that, despite the absence of a lethal impact, several sublethal effects involving gut and body size malformations, as well as the enhancement of apoptosis and oxidative stress in relation to an increase in tested concentration and a decrease in nanoparticle size.

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 Danioscope^TM 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.

The continuous and unregulated discharge of wastes and pollutants into the aquatic environment has required constant monitoring of the risks incurred by aquatic ecosystems. Alarmism arises from plastic pollution as larger artifacts release nanoscale fragments that can contact free-living stages such as gametes, embryos, and larvae. Specifically, the interaction between spermatozoa, released in water in externally fertilizing species, and the surrounding microenvironment is essential for successful fertilization. Activation and kinematics of movement, proper maintenance of ionic balance, and chemotactism are processes highly sensitive to even minimal perturbations caused by pollutants such as polystyrene nanoplastics. Spermatozoa of Mytilus galloprovincialis (M. galloprovincialis), an excellent ecotoxicological model, undergo structural (plasma membrane ruptures, DNA damage) and metabolic (reduced motility, fertilizing capacity) damage upon exposure to 50 nm amino-modified polystyrene nanoplastics (nPS-NH₂). Nanoplastics of larger diameter (100 nm) did not affect sperm parameters. The findings highlighted the negative impact that plastic pollution, related to nanoparticle diameter and concentration, could have on sperm quality and reproductive potential of organisms, altering the equilibrium of aquatic ecosystems.

TiO₂ and CeO₂ NPs are widely used in the medical field, for drug administration, oncological therapies, disinfection or diagnostic imaging. To date, their effects on aquatic ecosystems and their impacts on human health are little known but several scientific evidences show how CeO₂ NPs are able to store and release oxygen, giving them antioxidant activity against oxidative stress while TiO₂ NPs seem to be responsible for cytotoxicity and genotoxicity. In this study, the effects of combined nanoparticles, brookite TiO₂/CeO₂ nanocomposites, on A. salina nauplii following acute exposure were evaluated. Although the cytotoxicity of nanoparticles is generally dose-dependent and time-dependent, in the following investigation, exposure to combined nanoparticles, brookite TiO₂/CeO₂ nanocomposites, in A. salina nauplii would appear not to have had a statistically significant negative impact on the viability of the specimens. One of the mechanisms by which NPs exert toxic effects is the induction of oxidative stress. In this study, an assessment of potential oxidative stress and apoptotic damage on exposed organisms was conducted through the use of the DCFH₂DA probe and acridine orange. The results obtained suggest that although acute exposure to different concentrations of brookite TiO₂/CeO₂ nanocomposites did not have lethal effects, the positivity to DCFH₂DA and acridine orange observed does not exclude potential sublethal effects.

Paroxetine (PRX) is a common antidepressant, also frequently used by pregnant women to treat depression and anxiety associated with pregnancy; thus, we should increase warnings about its intake. The increased presence of paroxetine in the environment raises concerns about unintended exposure to it, with consequences for embryonic development. However, the effect of PRX on early embryonic development, particularly on the embryonic brain, is still poorly studied, so this study aimed to investigate its toxicological profile on embryonated eggs of Danio rerio. Embryos of D. rerio were exposed to 1, 10, and 100 μg/L of PRX using the ZFET test. The results showed that exposure to PRX does not interfere with embryonic development but causes adverse effects in larvae, including heartbeats and an inflammatory state, with production of ROS and apoptotic cells on their head. Finally, the immunofluorescence assay for the biomarker acetylcholinesterase showed a decrease in its activity in exposed groups. Therefore, paroxetine is able to reach the nervous system during embryonic development with negative consequences.