The molar ratio of Fe to Au is used as an index of internalized elements. In
the early time points (30 minutes and 1 hour), the OECM1 cells show the highest
Fe:Au ratio. Interestingly, the Fe:Au ratio in HT-29 cells is significantly lower than
in OECM1 cells (P = 0.0210; t-test), which correlates with HT-29 cells’ extreme
resistance to Fe@Au treatment