Quantitative single cell analysis of gold nanoparticle association across a mouse triple-negative breast cancer cell line and blood immune cell populations

In biomedical research, understanding the heterogeneity in nanoparticle association among different cell populations is crucial for translating to efficacy and immune identification. Using time-of-flight mass cytometry (CyTOF), we quantitatively assessed the association and distribution of gold nanoparticles (AuNPs) in murine breast cancer 4T1 cells and various immune cell populations in whole blood. Our findings reveal significant variability in gold nanoparticle accumulation across different cell types. In vitro, 4T1 cells co-cultured with 0.1 nM AuNPs had a median gold mass of 0.214 pg per cell which increased proportionally and significantly (P < 0.0001) to 2.418 pg per cell when exposed to 1 nM AuNPs. Regarding immune cell populations in mouse blood directly exposed to 0.1 nM AuNPs, heterogeneity in nanoparticle association varied across immune cell populations. We observed diverse levels of gold association (median, range pg/cell) in NK cells (0.0132, 0.0014-0.0265), dendritic cells (0.0131, 0.0004-0.0272), monocytes (0.0121, 0.0006-0.0272), granulocytes (0.0126, 0.0004-0.0272), B cells (0.0099, 0.0003-0.0274), CD4 T cells (0.0072, 0.0004-0.0226), and CD8 T cells (0.0062, 0.0006-0.1113). However, the single cell analysis revealed a monocyte subpopulation had the greatest association with AuNPs with almost 2 orders of magnitude greater association than NK cell median. These findings highlight the heterogeneous association of AuNPs with immune cell subsets in blood. This observation suggests that monocytes and dendritic cells display a higher propensity for interacting with and internalizing the nanoparticles, potentially due to specific receptor-mediated interactions and internalization mechanisms.