Quantifying Cytotoxicity and Cellular Uptake of Naked Gold Nanoparticles Using Total Reflection X‐Ray Fluorescence

ABSTRACT The study of the cytotoxic effects of gold nanoparticles (AuNP) is an active area of research. However, there is a lack of consistency in results with measures of cellular uptake relying on inductively coupled plasma (ICP)‐based methods, which introduce inconsistencies with sample preparation. There are also few papers examining the influence that the absolute amount of gold taken up by the cell, rather than the gold nanoparticle itself, has on toxicity, relying on ICP methods. In this work, total reflection x‐ray fluorescence (TXRF) spectroscopy was used to measure AuNP and the absolute amount of gold in epithelial breast cancer cells, and the cytotoxicity of 10 and 50 nm gold nano spheres and rods was analyzed with flow cytometry. With the calculation of absolute gold mass taken up by cancer cells from measurements of gold concentration, 10 nm diameter AuNP were found to be up to 6% more toxic than 50 nm. Our results agree with previous findings that 50 nm spheres are internalized most effectively, and rods are more toxic than spheres for the same number of nanoparticles. Both the linear quadratic and Hill model are suitable models to estimate the cytotoxicity of gold from AuNP uptake, exhibiting a better fit than the exponential model ( p < 0.05). This work shows that TXRF has excellent quantitative abilities for cellular and biological samples.