Quantification of silica nanoparticle uptake at environmentally relevant concentrations by gold-core embedding

The increasing use of silica nanoparticles (SiO₂ NPs) has raised concerns about potential human exposure. Assessing the health risks associated with SiO₂ NPs necessitates understanding their cellular uptake, yet measuring this uptake at low, environmentally relevant concentrations presents a significant challenge. In this study, we synthesized core-shell structured Au@SiO₂ NPs with diameters ranging from 50 to 200 nm and quantified their cellular uptake by analyzing the concentrations of Si and Au in A549 human lung carcinoma cells. No significant differences in cytotoxicity or cellular uptake were observed between Au@SiO₂ NPs and their core-less counterparts. Additionally, the comparable cellular uptake of Au@SiO₂ NPs, as evidenced by both Si and Au content, supports the use of the Au core as a tracer for SiO₂ NP uptake. The inclusion of the Au core facilitated the examination of SiO₂ NP uptake at concentrations an order of magnitude lower than previously possible, aligning more closely with environmental exposure levels. This is important because uptake at low concentrations cannot be accurately predicted from high-concentration data due to concentration-dependent changes in particle aggregation. Overall, Au@SiO₂ NPs provide a precise method for evaluating SiO₂ NP uptake at low concentrations, offering a more realistic assessment of their potential health risks compared to studies conducted at higher concentrations.