DescriptionIn large-scale scientific projects where nanomaterials need to be investigated by a number of research groups with different scientific background it is necessary to assure that all preparation and subsequent characterization procedures are as harmonized and inter-calibrated as possible. One major challenge is the preparation of stock dispersions from nanomaterials provided as powders as distinct dispersion procedures may introduce variability in the toxicity or characteristics that are measured. Stock dispersions are used in a variety of toxicological tests where aliquots of the stock suspension are typically added to the relevant test medium, e.g. cell culture medium. Furthermore, stock dispersions are required for particle characterization, as many techniques, like dynamic light scattering, laser diffraction, analytical ultracentrifugation, nanoparticle tracking analysis, are only able to measure aqueous samples. In order to obtain meaningful results and to allow cross-comparison of different toxicity and characterization tests and assays, it is therefore crucial to develop efficient and reproducible dispersion procedures. These harmonized and standardized protocols have not only to be efficient, but also be feasible in the majority of test laboratories. Common limitations include the availability of dispersion equipment in the involved laboratories and the access to analytical equipment for characterizing and checking the quality of the dispersions. Further a compromise has to be found regarding, the (maximum) concentration of the stock dispersion, the resulting stock dispersion volume, and the composition of the dispersion medium, because of the variety of (eco)toxicology tests with each having specific requirements. The presentation will summarize the major challenges and the corresponding solutions of the NANOSOLUTIONS project with regards to stock dispersion preparation. As a specific example the development of a common dispersion procedure for copper oxide nanoparticles with different surface functionalization (ammonium, carboxylate, or polyethylene glycol) will be presented. For this nanomaterial, a dispersion SOP was developed which included a calorimetric method for calibration of the delivered acoustic energy by adjustment of the probe-sonicator amplitude. Additionally, an SOP was established that described the conduction of dynamic light scattering (DLS) measurements for determination of hydrodynamic size and size-distribution of the nanoparticles in the final stock dispersion. The SOPs were tested by ten laboratories. In most cases deviations of the determined sizes could be explained with deviations from the procedure described in the SOP. The performed work showed that it is possible to obtain comparable stock dispersions in different laboratories if carefully prepared SOPs are provided which consider the most important parameters that influence the dispersion process and the following characterization step. Acknowledgements: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 309329.
|8 Feb 2017
|New tools and approaches for nanomaterial safety assessment 2017