The rapid development of nanotechnology and its application in all areas of life not only provides many chances, but also poses potential risks for users and their environment. Modern health-based risk assessment strategies for nanomaterials include three major pillars: analytical data about surface chemistry, composition and size distribution patterns of manufactured nanomaterials (NMs), toxicological data from in vitro experiments and lastly also from in vivo experiments. This thesis provides scientific advancements for each of the three pillars, in order to enhance a holistic health based risk assessment approach for nanomaterials. The chemical characterization, quantification and the determination of size distributions is a key issue in defining a NM and predicting its interactions. In the context of the research work of this dissertation, a further development of the single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) technique is presented. With the help of this method the fast and reliable size distribution characterization of metal containing NMs is now possible. The new approach is based on the application of a dual sample introduction system using both, a pneumatic nebulizer and a micro droplet generator. The design of the system allows a comprehensive size characterization of NMs within 20 minutes. The obtained data is evaluated using three approaches presented in the thesis. Each of these approaches is based on a unique calibration principle. Thus, this work contributes to an independent and precise analytical characterization of NMs. Furthermore, in order to gain insights into the solubility behavior of NMs after oral uptake a in vivo toxicological assessment was carried out. Aluminum-containing NMs (Al2O3 and Al0) were administered to rats via oral gavage for three-days and the aluminum organ burden was determined. The comparatively low exposure level in combination with the ubiquitous aluminum background posed a challenge for conventional analytical techniques. We solved this problem in the present study by means of a matrix calibration and the application of a daily response factor, which enabled us not only to reliably determine the applied materials in organic matrices, but also to obtain information on the uptake and distribution of the two NMs. A special focus was laid on the differences in the uptake of the NMs and the subsequent distribution of the materials in the intestinal and systemic organs (liver, kidney, spleen). Our work has shown that the materials behave significantly different, irrespective of similar size and composition. Especially shape and surface properties of the NM could be identified as decisive factors for these differences. Moreover, in vitro experiments with the two aluminum containing NMs in human keratinocytes were carried out to further investigate the cellular uptake and intracellular distribution as well as the resulting metabolic changes within the cell. In order to make the exposure scenario more realistic and mimic ingredients of cosmetic products, the influence of the two bioactive vitamins A and D3 was tested in addition to the two NMs. The ICP-MS results showed significant differences between the uptake of the two NMs after addition of the vitamins. Time of Flight secondary ion mass spectrometry (ToF-SIMS) was then used to further investigate metabolic changes in the cell. It was found that the increased uptake of Al0 NMs after vitamin D3 addition was due to a loss of cell membrane integrity. The combination of Al2O3 NM and vitamin D3 led to an increase in membrane stability. However, the exact difference could not be conclusively clarified in the study. Our results indicate the need for further research to identify which properties of a NM are decisive for the observed different interactions. In summary, this work contributes to a more precise characterization and detection of NMs and to a better explanation of their interactions with biological systems. The pillar based methodology can be used for future research and thus contributes to a safer and more reliable application of nanotechnology without major health risks.
