Natural organic matter composition and nanomaterial surface coating determine the nature of platinum nanomaterial-natural organic matter corona

Ecotoxicity studies of two atrazine nanoformulations: From the evaluation of stability in media to the effects on aquatic organisms

In the field of agriculture, nanopesticides have been developed as an alternative to the conventional pesticides, being more efficient for pest control. However, before their widespread application it is essential to evaluate their safe application and no environmental impacts. In this paper, we evaluated the toxicological effects of two kinds of atrazine nanoformulations (ATZ NPs) in different biological models (Raphidocelis subcapitata, Danio rerio, Lemna minor, Artemia salina, Lactuca sativa and Daphnia magna) and compared the results with nanoparticle stability over time and the presence of natural organic matter (NOM). The systems showed different characteristics for Zein (ATZ NPZ) (184 ± 2 nm with a PDI of 0.28 ± 0.04 and zeta potential of (30.4 ± 0.05 mV) and poly(epsilon-caprolactone (ATZ PCL) (192 ± 3 nm, polydispersity (PDI) of 0.28 ± 0.28 and zeta potential of -18.8 ± 1.2 mV) nanoparticles. The results showed that there is a correlation between nanoparticles stability and the presence of NOM in the medium and Environmental Concentrations (EC) values. The stability loss or an increase in nanoparticle size result in low toxicity for R. subcapitata and L. minor. For D. magna and D. rerio, the presence of NOM in the medium reduces the ecotoxic effects for ATZ NPZ nanoparticles, but not for ATZ NPs, showing that the nanoparticles characteristics and their interaction with NOM can modulate toxic effects. Nanoparticle stability throughout the evaluation must be considered and become an integral part of toxicity protocol guidelines for nanopesticides, to ensure test quality and authentic results regarding nanopesticide effects in target and non-target organisms.

Insights into eco-corona formation and its role in the biological effects of nanomaterials from a molecular mechanisms perspective

Broad application of nanotechnology inevitably results in the release of nanomaterials (NMs) into the aquatic environment, and the negative effects of NMs on aquatic organisms have received much attention. Notably, in the natural aquatic environment, ubiquitous ecological macromolecules (i.e., natural organic matter, extracellular polymeric substances, proteins, and metabolites) can easily adsorb onto the surfaces of NMs and form an "eco-corona". As most NMs have such an eco-corona modification, the properties of their eco-corona significantly determine the fate and ecotoxicity of NMs in the natural aquatic ecosystem. Therefore, it is of great importance to understand the role of the eco-corona to evaluate the environmental risks NMs pose. However, studies on the mechanism of eco-corona formation and its resulting nanotoxicity on aquatic organisms, especially at molecular levels, are rare. This review systemically summarizes the mechanisms of eco-corona formation by several typical ecological macromolecules. In addition, the similarities and differences in nanotoxicity between pristine and corona-coated NMs to aquatic organisms at different trophic levels were compared. Finally, recent findings about potential mechanisms on how NM coronas act on aquatic organisms are discussed, including cellular internalization, oxidative stress, and genotoxicity. The literature shows that 1) the formation of an eco-corona on NMs and its biological effect highly depend on both the composition and conformation of macromolecules; 2) both feeding behavior and body size of aquatic organisms at different trophic levels result in different responses to corona-coated NMs; 3) genotoxicity can be used as a promising biological endpoint for evaluating the role of eco-coronas in natural waters. This review provides informative insight for a better understanding of the role of eco-corona plays in the nanotoxicity of NMs to aquatic organisms which will aid the safe use of NMs.

Insight into the formation and biological effects of natural organic matter corona on silver nanoparticles in water environment using biased cyclical electrical field-flow fractionation

Natural organic matter (NOM) readily interacts with nanoparticles, leading to the formation of NOM corona structures on their surface. NOM corona formation is closely related to the surface coatings and bioavailability of nanoparticles. However, the mechanism underlying NOM corona formation on silver nanoparticles (AgNPs) remains largely unknown due to the lack of effective analytical methods for identifying the changes in the AgNP surface. Herein, the separation ability of biased cyclical electrical field-flow fractionation (BCyElFFF) for same-sized polyvinyl pyrrolidone-coated and poly(ethylene glycol)-coated silver nanoparticles (AgNPs) with different electrophoretic mobilities was evaluated under various electrical conditions. Then, the mechanism behind the NOM corona formation on these AgNP surfaces was elucidated based on the changes in the elution time and off-line characterization of the collected fractions during their elution time in a BCyElFFF run. Finally, the survival rates of E. coli exposed to polyvinyl pyrrolidone-coated and poly(ethylene glycol)-coated AgNPs with or without NOM collected during repeated BCyElFFF runs were observed to increase with increasing NOM concentration, clearly demonstrating the negative effect of NOM corona structures on the bioavailability of AgNPs. These findings highlight the powerful separation and isolation ability of BCyElFFF in studying the transformation and fate of nanoparticles in aqueous environments.

Aquatic organisms modulate the bioreactivity of engineered nanoparticles: focus on biomolecular corona

The increased use of nanoparticle (NP)-enabled materials in everyday-life products have raised concerns about their environmental implications and safety. This motivated the extensive research in nanoecotoxicology showing the possibility that NPs could cause harm to the aquatic organisms if present at high concentrations. By contrast, studies dealing with influence that organisms could exert on the fate and thus effects of NPs are still very rare. Drawing on the existing up-to-date knowledge we critically discuss the formation of biomolecular corona as one of the mechanisms by which organisms exerted control on the NPs fate in the aquatic and biotic environments. We focused the formation of corona by exogeneous and endogenous biomolecules and illustrated the discussion with the specific example of phytoplankton and aquatic invertebrate species. We highlighted the necessity to incorporate the concept of biomolecular corona within more general framework considering the feedback of aquatic organisms and the control they exert in shaping the fate and impact of NPs in the aquatic and biological environment. In our view such broader perspective will contribute to get novel insights into the drivers of environmental transformations of NPs and their mechanisms, which are important in environmental risk assessment.