To assess cell morphology, cells were seeded on number 1, 13 mm diameter glass coverslips 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