| 1. |
- Badetti, Elena, et al.
(författare)
-
Novel multimethod approach for the determination of the colloidal stability of nanomaterials in complex environmental mixtures using a global stability index: TiO2 as case study
- 2021
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 801
-
Tidskriftsartikel (refereegranskat)abstract
- A systematic study on the colloidal behavior of uncoated and polyvinylpyrrolidone (PVP) coated TiO2 engineered nanomaterials (ENMs) in simulated aqueous media is herein reported, in which conditions representative for natural waters (pH, presence of divalent electrolytes (i.e. Ca2+/Mg2+ and SO42−), of natural organic matter (NOM) and of suspended particulate matter (SPM)) were systematically varied. The colloidal stability of the different dispersions was investigated by means of Dynamic and Electrophoretic Light Scattering (DLS and ELS) and Centrifugal Separation Analysis (CSA), and a global stability index based on these three techniques was developed. The index allows to quantitatively classify the nano-based dispersions according to their colloidal stability affected by the different parameters studied. This multimethod approach clearly identifies inorganic SPM followed by divalent electrolytes as the main natural components destabilizing TiO2 ENMs upon entering in simulated natural waters, while it highlights a moderate stabilization induced by NOM, depending mainly on pH. Moreover, the PVP coating was found to attenuate the influence of these parameters on the colloidal stability. The obtained results show how the global stability index developed is influenced by the complexity of the system, suggesting the importance of combining the information gathered from all the techniques employed to better elucidate the fate and behavior of ENMs in natural surface waters.
|
|
| 2. |
|
|
| 3. |
- Hassellöv, Martin, 1970, et al.
(författare)
-
Iron Oxides as Geochemical Nanovectors for Metal Transport in Soil-River Systems
- 2009
-
Ingår i: Elements. - : Mineralogical Society of America. - 1811-5209 .- 1811-5217. ; 4:6, s. 401-406
-
Tidskriftsartikel (refereegranskat)abstract
- Topsoils are often contaminated by trace metals, and it is important to understand how different processes govern the transport of such metals to fresh and marine waters. This paper presents measurements of natural nanoparticles and colloidal organic matter in soil and river samples from Germany and Sweden. In our analytical approach, a nanoparticle separation technique is combined with multielement detection and applied to soil and river samples to link the macroscale field observations with detailed molecular studies in the laboratory. It was determined that lead is associated with iron oxide colloids, which are ubiquitous nanoparticles that can be efficiently transported. Eventually both iron oxides and lead are removed by flocculation under conditions of estuarine mixing. Iron-rich nanoparticles compete efficiently with natural organic matter (NOM) complexation for lead binding in both the soil and river systems studied.
|
|
| 4. |
- Nowack, Bernd, et al.
(författare)
-
Progress towards the validation of modeled environmental concentrations of engineered nanomaterials by analytical measurements
- 2015
-
Ingår i: Environmental Science: Nano. - 2051-8153. ; 2:5, s. 421-428
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental exposure modeling has been used extensively in the last years to obtain estimates of environmental concentrations of engineered nanomaterials (ENMs). In this perspective piece, we explore the issues when aiming to validate modeled environmental concentrations and propose options for both modelers and analytical chemists on how to proceed in the future to better compliment one another's efforts. In this context, validation means to determine the degree to which the simulation results from a model are accurate representations of the real world by comparison with analytical data. Therefore, for such a model validation procedure, analytical methods need to be available which provide information in the same subject area. Currently, a major issue with nanometrology is that a multitude of nanomaterials are present in natural systems but only some are ENMs; various other particles of natural origin are abundant in the same systems. The analytical tools available are not yet capable to distinguish the natural from engineered nanomaterials at the low ENM concentrations expected in complex environmental matrices. However, both modeling and analytical studies are able to provide an orthogonal view on nanomaterials: modeling is able to yield estimates of the presence of ENMs in various environmental compartments while analytics can provide physical characterization of ENMs in these systems with hints towards the total nanomaterial concentration. While we need to make strides to improve the two approaches separately, using the resulting data together in a mutually supportive way will advance the field of ENM risk assessment.
|
|
| 5. |
|
|
| 6. |
- Stone, Vicki, et al.
(författare)
-
Nanomaterials for environmental studies: classification, reference material issues, and strategies for physico-chemical characterisation.
- 2010
-
Ingår i: Science of the total environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 408:7, s. 1745-54
-
Tidskriftsartikel (refereegranskat)abstract
- NanoImpactNet is a European Commission Framework Programme 7 (FP7) funded project that provides a forum for the discussion of current opinions on nanomaterials in relation to human and environmental issues. In September 2008, in Zurich, a NanoImpactNet environmental workshop focused on three key questions: 1. What properties should be characterised for nanomaterials used in environmental and ecotoxicology studies? 2. What reference materials should be developed for use in environmental and ecotoxicological studies? 3. Is it possible to group different nanomaterials into categories for consideration in environmental studies? Such questions have been, at least partially, addressed by other projects/workshops especially in relation to human health effects. Such projects provide a useful basis on which this workshop was based, but in this particular case these questions were reformulated in order to focus specifically on environmental studies. The workshop participants, through a series of discussion and reflection sessions, generated the conclusions listed below. The physicochemical characterisation information identified as important for environmental studies included measures of aggregation/agglomeration/dispersability, size, dissolution (solubility), surface area, surface charge, surface chemistry/composition, with the assumption that chemical composition would already be known. There is a need to have test materials for ecotoxicology, and several substances are potentially useful, including TiO(2) nanoparticles, polystyrene beads labelled with fluorescent dyes, and silver nanoparticles. Some of these test materials could then be developed into certified reference materials over time. No clear consensus was reached regarding the classification of nanomaterials into categories to aid environmental studies, except that a chemistry-based classification system was a reasonable starting point, with some modifications. It was suggested, that additional work may be required to derive criteria that can be used to generate such categories, that would also include aspects of the material structure and physical behaviour.
|
|
| 7. |
- Urey, Carlos, et al.
(författare)
-
Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles
- 2016
-
Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173. ; 513:1-2, s. 309-318
-
Tidskriftsartikel (refereegranskat)abstract
- For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability.
|
|
| 8. |
- Weiss, Victor U., et al.
(författare)
-
Nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) of liposomes : Applicability of the technique for nano vesicle batch control
- 2016
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 141:21, s. 6042-6050
-
Tidskriftsartikel (refereegranskat)abstract
- Liposomes are biodegradable nanoparticle vesicles consisting of a lipid bilayer encapsulating an aqueous core. Entrapped cargo material is shielded from the extra-vesicular medium and sustained release of encapsulated material can be achieved. However, application of liposomes as nano-carriers demands their characterization concerning size and size distribution, particle-number concentration, occurrence of vesicle building blocks in solution and determination of the resulting vesicle encapsulation capacity. These questions can be targeted via gas-phase electrophoretic mobility molecular analysis (GEMMA) based on a nano electrospray (nES) charge-reduction source. This instrument separates single-charged nanoparticles in the gas-phase according to size in a high-laminar sheath-flow by means of an orthogonal, tunable electric field. nES GEMMA analysis enables to confirm liposome integrity after passage through the instrument (in combination with atomic force microscopy) as well as to exclude vesicle aggregation. Additionally, nanoparticle diameters at peak apexes and size distribution data are obtained. Differences of hydrodynamic and dry particle diameter values, as well as the effect of number- and mass-based concentration data analysis on obtained liposome diameters are shown. Furthermore, the repeatability of liposome preparation is studied, especially upon incorporation of PEGylated lipids in the bilayer. Finally, the instruments applicability to monitor mechanical stress applied to vesicles is demonstrated.
|
|
