Under bright-field microscopy (Figure 2) and high-resolution SEM (Figure 3), no structural difference in cell morphology was found when cells were treated for 24 hours – the time window to observe apoptosis and necrosis morphologically30,31 – and this was comparable to control conditions. The density of cells markedly decreased upon Fe@Au exposure, which is in accordance with the results shown in Figure 1. However, the molecular analysis of cells for apoptosis and necrosis showed that there was no statistically significant increase in the rate of apoptosis or necrosis in Fe@Au-treated cells