CRC and OECM1 were treated with Fe-only nanoparticles (Fe NPs) and Fe@Au nanoparticles (Fe@Au NPs) for 48 hours, analyzed by WST-1. OECM1 and Caco-2 are more sensitive to Fe nanoparticles; whereas, the other CRC , (HT-29 and SW480) are more resistant to Fe nanoparticles than to Fe@Au nanoparticles.