Our research also suggests that the resistance to Fe@Au treatment may rely on the ability to cope with Fe. Fe-resistant cells may either have a more robust mitochondrial system or a more effective efflux system, such as ferroportin, to eliminate the Fe. Ferroportin is a protein that serves as a transmembrane ion channel to enable Fe efflux from cells36 and is expressed in hepatic cells, macrophages, and also in enterocytes.37 More research is needed to further investigate this hypothesis and elucidate the full mechanisms of Fe@Au sensitivity in cancer cells.