I. D. Nordhorn, A. Vennemann, M. Wiemann, U. Karst

University of Münster, Institute of Inorganic and Analytical Chemistry, Corrensstraße 28/30, 48149 Münster

Size distributions analysis by single particle inductively coupled plasma-mass spectrometry (spICP-MS) is widely used to investigate nanoparticle suspensions. Here, information about the particle size and number concentration as well as the elemental composition is obtained. In combination with a laser ablation (LA) system, spICP-MS analysis can be performed directly for solid samples without the need for additional sample preparation steps such as digestion or extraction. Furthermore, the spatial information of the nanoparticle distribution is preserved. As LA-spICP-MS is still an emerging technique, critical parameters and limitations have to be identified. We therefore evaluated the influence of several laser ablation parameters as spot size, scan speed, and laser fluence on the particle size distribution by analyzing gold nanoparticles of known sizes embedded in gelatin. The developed method was then applied to biological samples by analyzing tissue thin sections from rats that were exposed to gold and silver nanoparticles (NP) by intratracheal instillation. AuNP were found to stay intact and do not tend to agglomerate or disintegrate during translocation and within 3 days of capture in the splenic parenchyma. The analysis of AgNP was of special interest as they can be a source of toxic Ag⁺. Monitoring the size distribution can reveal the possible release of Ag⁺ from AgNP within the tissue and contribute to the understanding of the toxicity mechanism of AgNP. In our study, we analyzed liver thin sections of rats exposed to AgNP of different size distributions and surface modifications. Our results show that applying LA-spICP-MS for size distribution analysis in extrapulmonary organs is a powerful tool to access the particle translocation from the lungs to remote organs. With this method, the distribution of nanoparticles in organ tissues as well as particle degradation or aggregation can be monitored.