Decoding Live Cell Interactions with Multi-Nanoparticle Systems: Differential Implications for Uptake, Trafficking, and Gene Regulation.

Surface modification with oligonucleotides renders gold nanoparticles to endocytose through very different pathways as compared to unmodified ones. Such oligonucleotide-modified gold nanoparticles (OGNs) have been exploited as effective nanocarriers for gene regulation therapies. Notably, in an effort to reduce overall dosage and provide safer transition to the clinic, cooperative systems composed of two or more discrete nanomaterials have been recently proposed as an alternative to intrinsically multifunctional nanoparticles. Yet, our understanding of such systems designed to synergistically cooperate in their diagnostic or therapeutic functions remains acutely limited. Specifically, cellular interactions and uptake of OGNs are poorly understood when the cell simultaneously interacts with other types of nanoparticles. Here, we investigated the impact of simultaneous uptake of similar-sized iron oxide nanoparticles (IOPs) on the endocytosis and gene regulation function of OGNs, whose analogues have been proposed for sensitization, targeting, and treatment of tumors. We discovered that both the OGN uptake amount and, remarkably, the gene regulation function remained stable when exposed to a very wide range of extracellular concentrations of IOPs. Additionally, the co-localization analysis showed that a proportion of OGNs was co-localized with IOPs inside cells, which hints at the presence of similar trafficking pathways for OGNs and IOPs following endocytosis. Taken together, our observations indicate that while the OGN endocytosis is highly independent of the IOP endocytosis, it shares transport pathways inside cells-but does so without affecting the gene regulation behavior. These results provide key insights into concomitant interactions of cells with diverse nanoparticles and offer a basis for the future design and optimization of cooperative nanomaterials for diverse theranostic applications.