Total X‐Ray Fluorescence Measurement of Spherical Gold Nanoparticle Uptake by <scp>PC</scp> ‐3 Cells: Dual‐Phase Kinetic Uptake and Modelling

ABSTRACT The literature on the cellular uptake of gold nanoparticles (AuNPs) is currently limited in long‐term studies (&gt; 10 h) and the applicability of mathematical uptake models to experimental data. Here, the uptake of AuNPs of diameters 5, 10, and 20 nm at concentrations of 10 and 40 μM was measured up to 48 h in PC‐3 cells. Total reflection x‐ray fluorescence (TXRF) spectroscopy was used for quantification. AuNP uptake was observed to increase with higher extracellular concentration and to have an inverse‐size dependency. Uptake kinetics were fundamentally similar across all conditions, with two plateaus. A new kinetic model of AuNP uptake was developed with two phases of uptake. The second phase had significantly higher uptake than the first. This model fits the experimental data well, with R 2 values ranging from 0.8298 to 0.9876. Rate constants of uptake were found to decrease with AuNP diameter, across both uptake phases. In addition to the insight into NP cellular interactions, this work also showcases the strong capabilities of TXRF as a cellular analysis tool.