Figure 5

AFM topography images of SH-SY5Y cells. A) control cells without MNPs, B) cells incubated with 25 µgmL^-1 MNP-PEI and C) MNP-PEI-PEG over 1) 1 h, 2) 4 h, 3) 24 h and 4) 72 h. Cells were fixed after incubation and AFM imaging was performed in air using a RTESPA tip of spring constant 40 N/m, carrying out 896 scans/line at a scan rate of 0.32 Hz and 1.102 V amplitude.