A single-cell inductively coupled plasma mass spectrometry technique was used to explore the influence of particle properties on the association of nanomaterials (NMs) with algal cells. We... Show moreA single-cell inductively coupled plasma mass spectrometry technique was used to explore the influence of particle properties on the association of nanomaterials (NMs) with algal cells. We investigated the effect of particle size, shape, and surface chemistry [citrate and natural organic matter (NOM) coating] on the association of gold (Au) NMs with algal cells using particle mass, particle number, surface area (SA), and volume-specific surface area (VSSA) as dose metrics. Particle number was found to be a better dose metric than particle mass, SA, and VSSA in view of the strong correlation obtained between the number of associated Au NMs with cells and the number of Au NMs in the exposure medium. When particle number was used as the dose metric, there was no selectivity of Au NM cellular association irrespective of particle size and shape, and the cellular association was proportional to the effective number of particles to which the cells were exposed. The surface chemistry of the Au NMs, however, decreased the level of cellular association of some NMs (60 nm spheres). Particle number is the main element used for the classification of NMs according to the recommended definition for NM by the European Commission. The key finding of our study supports the implementation of this definition for safety purposes. Show less
Suitable methods and fit-for-purpose techniques are required to allow characterization of carbon-based nanomaterials (CB-NMs) in complex matrices. In this study, two methods were developed; a... Show moreSuitable methods and fit-for-purpose techniques are required to allow characterization of carbon-based nanomaterials (CB-NMs) in complex matrices. In this study, two methods were developed; a method for extraction and characterization of CB-NMs in biological media and a method for fractionation of natural organic matter (NOM) coated CB-NMs in environmental matrices. The former method was developed by extracting carbon nanotubes (CNTs: sized 0.75 × 3000 nm) and nanoplastics (sized 60, 200 and 600 nm) from eggshells and characterizing the extracted CB-NMs in terms of particle size distribution using asymmetrical flow field-flow fractionation (AF4) coupled with multi-angle light scattering (MALS). The latter method was developed using AF4-MALS to fraction NOM-coated CNT (sized 0.75 × 3000 nm) and nanoplastics (sized 60, 200 and 300 nm) in a simulated natural surface water and provide information about the size distribution of the CB-NM-NOM complexes. The developed AF4-MALS method successfully fractioned the CB-NM-NOM complexes based on hydrodynamic size and provided the size distribution of the complexes. The NOM corona did not shift significantly the median size of the CB-NMs. It influenced however the size distribution of the nanoplastics and CNTs. The sample preparation method failed to extract the CNTs (recovery < 20%) from the matrices of the eggshells while being successful for extracting the nanoplastics (recoveries > 60%). The AF4-MALS fractogram showed that the extraction method did not significantly influence the size distribution of the nanoplastics of 60 and 200 nm size, whereas the peak of 600 nm nanoplastics shifted towards a smaller hydrodynamic size. In conclusion, the developed sample preparation method followed by the developed AF4-MALS method can be applied for extraction, separation and characterization of CB-NMs in biological and environmental matrices. Thus, the methods have a high potential to be methods of choice to investigate CB-NMs in future studies. Show less
Some metal-based engineered nanoparticles (ENPs) undergo fast dissolution and/or aggregation when they are released in the environment. The underlying processes are controlled by psychochemical... Show moreSome metal-based engineered nanoparticles (ENPs) undergo fast dissolution and/or aggregation when they are released in the environment. The underlying processes are controlled by psychochemical/biological parameters of the environment and the properties of the particles. In this study, we investigated the interaction between algal cells and zero valent copper nanoparticles (Cu0-ENPs) to elucidate how the cells influence the dissolution and aggregation kinetics of the particles and how these kinetics influence the cellular uptake of Cu. Our finding showed that the concentration of dissolved Cu ([Cu]dissolved) in the supernatant of the culture media without algal cells was higher than the [Cu]dissolved in the media with algal cells. In the absence of the cells, dissolved organic matter (DOC) increased the dissolution of the particle due to increasing the stability of the particles against aggregation, thus increasing the available surface area. In the presence of algae, Cu0-ENPs heteroaggregated with the cells. Thus, the available surface area decreased over time and this resulted in a low dissolution rate of the particles. The DOC corona on the surface of the particles increased the heteroaggregation of the particles with the cells and decreases the uptake of the particles. Our findings showed that microorganisms influence the fate of ENPs in the environment, and they do so by modifying the dissolution and aggregation kinetics of the Cu0-ENPs. Show less
The combined effects of pH, dissolved organic carbon (DOC) and Ca2+/Mg2+ on the dissolution and aggregation kinetics of zero valent copper engineered nanoparticles (Cu0 ENPs) were investigated. The... Show moreThe combined effects of pH, dissolved organic carbon (DOC) and Ca2+/Mg2+ on the dissolution and aggregation kinetics of zero valent copper engineered nanoparticles (Cu0 ENPs) were investigated. The dissolution and aggregation of the particles were studied in (a) synthetic aqueous media, similar in chemistry to natural surface waters, and (b) natural surface waters samples, for up to 32 or 24 h. The DOC stabilized the particles and prevented aggregation, and thus increased the available surface area. The higher available surface area in turn accelerated the dissolution of the particles. The presence of Ca2+/Mg2+, however, changed the aggregation and the dissolution of the DOC-stabilized particles. The influence of Ca2+/Mg2+ on DOC-stabilized particles was different at different pH's. In the absence of DOC, 10 mM of Ca2+/Mg2+ induced charge reversal on the particles and caused particle stability against aggregation. This subsequently increased particles dissolution. The results obtained with regard to dissolution and aggregation of the particles in natural surface waters were compared with those determined for the synthetic waters. This comparison showed that the behavior of the particles in the natural surface waters was mostly similar to the behavior determined for media at pH 9. Overall, the current study provides some novel insights into the simultaneous effects of physicochemical parameters of water on particle stability against aggregation and dissolution, and provides data about how the processes of aggregation and dissolution of Cu0 ENPs interact and jointly determine the overall particle fate. Show less
