Seminar: Steffen Hellmann

The study of nanoparticles (NPs) has had increasing focus over the past few decades. NPs are common additives to a large number of industrial products due to their beneficial properties in many application fields, such as in cement paste. However, the versatile usage of NPs has led to a high distribution of NPs in the environment and their potential ecotoxicological danger is still in the early stage of research. Particularly, the characterisation of (nano)particles is still elaborate, especially if aiming to receive particle sizes, number concentration and their elemental composition in one measurement. Those parameters can be measured directly from suspension in different matrices (e.g. H2O, ethanol) using a relatively new methodology: single particle (sp) ICP-MS. Here, we will provide an overview of the method and its data interpretation as well as recent applications. In our first study, we investigated early hydration cement (nano)particles which was only possible directly in ethanol to prevent further hydration (growing of the particles) and therefore developed a new method to tackle ethanol-based interferences. This study showed the successful characterisation of reference materials as well as good agreement of measured Ca/Si ratios. SpICP-MS can also be used to study metals associated with biological cells < 5 μm which is then called single cell (sc) ICP-MS. ScICP-MS was applied to investigate the heavy metal bioremediation potential of soil bacteria (Streptomyces coelicolor). In this work, we evaluated the interaction mechanism of S. coelicolor spores, which are well suitable for scICP-MS because of their spherical shape, with Ce, Cd and U and distinguished between strong association such as incorporation vs. weak association such as adsorption. Results suggested that the interaction mechanism starts with relevant adsorption onto the spore surface and that after growing spores in HM-amended media, only Ce and U but not Cd were strongly spore associated. This study provides more light into a simple and efficient procedure to quantify HM–cell interactions, useful for bioremediation works. In a nutshell, sp/scICP-MS is a valuable tool to quantitatively investigate (nano)particles and biological cells regarding their size, concentration and elemental composition in one measurement whose importance will very likely increase in the next decades.