Inorganic Nanoparticle and Nanoplastic Transformations and the Impact on Biouptake by Freshwater Algal Cells Using Single Cell and Single Particle Inductively Coupled Plasma Mass Spectrometry

The ubiquitous presence of nanoparticles (NPs) and nanoplastics (NPPs) and their effects on environmental and human health is a significant concern. They are used in every aspect of our lives, and while they offer many benefits, there are concerns about their impacts on ecosystems and human health. The primary aim of this dissertation is to quantify NP and NPP transformations in the presence of algae and determine how those transformations influence bioavailability. The methodology involves two complementary analytical techniques: single particle (SP) and single cell (SC) inductively coupled plasma mass spectrometry (ICP-MS). These techniques are tested and applied to two freshwater microalgal cell types after exposing them to inorganic NPs, including gold (Au), silver-shelled gold (Au@Ag), and palladium NPPs. Post-exposure, cells were separated from the cell suspension to remove dispersed NPs and NPPs that were not cell-associated. Cell-associated NPs and NPPs were then measured by SC-ICP-MS and the dispersed NPs and NPPs removed during the wash steps were quantified using SP-ICP-MS. Experiments showed that 80% of cells are lost during the sample preparation. Due to the loss of cells during cell suspension preparation, cells must be grown to a concentration of approximately 400,000 cells mL-1 to ensure enough cells remain for SC-ICP-MS. Each cell type must be optimized before analysis by SC-ICP-MS. It was found that NPs and NPPs are cell-associated post-exposure, and individual cells will typically have at least one cell-associated NP (Au and Au@Ag). Cell exposure to varying concentrations of Au and Au@Ag nanoparticles for the same duration did not result in an increased number of cell-associated nanoparticles at higher concentrations. However, when exposing cells to Au and Au@Ag NPs for a longer duration (e.g., 72 hours versus 48 hours), cells showed an increase in cell-associated NPs. When exposing the same cells to Pd@PAN NPPs, it was found that NPPs agglomerate both in the cell suspension and when cell-associated, with each cell having at least one agglomerate consisting of 300 Pd NPPs. Single particle and single cell ICP-MS provide a means for understanding NP and NPP transformations in complex media at environmentally relevant concentrations and how those transformations result in their biouptake. This can yield important information on the ecological and human impact of exposure. The methods described in this dissertation can be applied to a wide range of cell types to provide quantitative data on how nano-sized materials transform and are taken up on a cell-by-cell basis.