Embryotoxicity of silver nanomaterials (Ag NM300k) in the soil invertebrate Enchytraeus crypticus - Functional assay detects Ca channels shutdown

Co-Exposure of Nanopolystyrene and Other Environmental Contaminants-Their Toxic Effects on the Survival and Reproduction of Enchytraeus crypticus

Plastics in all shapes and sizes have become widespread across ecosystems due to intense anthropogenic use. As such, they can interact with other contaminants that accumulate in the terrestrial environment, such as pharmaceuticals, metals or nanomaterials (NMs). These interactions can potentiate combined toxic effects in the exposed soil organisms, with hazardous long-term consequences to the full ecosystem. In the present study, a terrestrial model species, Enchytraeus crypticus (oligochaeta), was exposed through contaminated soil with nanopolystyrene (representative of nanoplastics (NPls)), alone and in combination with diphenhydramine (DPH, representative of pharmaceuticals), silver nitrate (AgNO₃, representative of metals) and vanadium nanoparticles (VNPs, representative of NMs). AgNO₃ and VNPs decreased E. crypticus reproduction at 50 mg/kg, regardless of the presence of NPls. Moreover, at the same concentration, both single and combined VNP exposures decreased the E. crypticus survival. On the other hand, DPH and NPls individually caused no effect on organisms' survival and reproduction. However, the combination of DPH (10 and 50 mg/kg) with 300 mg NPls/kg induced a decrease in reproduction, showing a relevant interaction between the two contaminants (synergism). Our findings indicate that the NPls can play a role as vectors for other contaminants and can potentiate the effects of pharmaceuticals, such as DPH, even at low and sub-lethal concentrations, highlighting the negative impact of mixtures of contaminants (including NPls) on soil systems.

Reactive Oxygen Species Detection Using Fluorescence in Enchytraeus crypticus-Method Implementation through Ag NM300K Case Study

An imbalance between reactive oxygen species (ROS) and antioxidants in a living organism results in oxidative stress. Measures of such imbalance can be used as a biomarker of stress in ecotoxicology. In this study, we implemented the ROS detection method based on the oxidant-sensing probe dichloro-dihydro-fluorescein diacetate (DCFH-DA), detected by fluorescence microscopy, in Enchytraeus crypticus adults and cocoons, i.e., also covering the embryo stage. Hydrogen peroxide (H2O2), a well-known ROS inducer, was used both to optimize the method and as positive control. Implementation was successful, and the method was used to assess ROS formation in E. crypticus cocoons and adults when exposed to the reference silver nanomaterial Ag NM300K, at two effect concentrations (EC20 and EC50) for both hatching and reproduction over 3 and 7 days. The measured ROS levels varied with time, concentration, and developmental stage, with higher levels detected in adults compared with cocoons. In cocoons, ROS levels were higher at the EC20 than the EC50, which could be explained by non-monotonic concentration-response curve for hatching and reproduction, as previously observed. The increase in ROS levels at day 3 preceded the oxidative damage, as reported to occur later (day 7) in adults. The DCFH-DA method was successfully implemented here and can be further used as a new tool to detect ROS formation in E. crypticus, especially after short-term exposure to chemicals, including nanomaterials. We recommend the use of 3 and 7 days in the exposure design for this assessment.