To assess cell morphology, cells were seeded on number 1, 13 mm diameter glass coverslips (catalog number G402, ProSciTech Proprietary Limited, Kirwan, QLD, Australia) and allowed to attach for 24 hours. Cells were then treated with Fe@Au for 24 hours. OECM1 cells were treated with 10 μg/mL Fe@Au, while CRC cells were treated with 50 μg/mL, which are about the half-maximal inhibitory doses. Cells were washed and fixed in 4% paraformaldehyde in PBS for 15 minutes. Cells were then mounted on the glass slides and sealed with nail polish for imaging with differential interference contrast (DIC) microscopy