Figure 6.

Transfection efficiency and cell viability with respect to variable distance: MCF7 cells are transfected with 60 μg of PEI (polyethyleneimine) or PS (PEI-coated superparamagnetic iron oxide nanoparticles (SPION)) together with 10 μg of GFP-DNA and then exposed to a magnetic field for 1 h. After incubation of cells at 37 °C for an additional 2 h, transfection solutions are removed by washing with PBS, and the culture was maintained in fresh DMEM medium until incubation time is achieved to 48 h. (a–f) GFP expression is observed by inverted fluorescence microscopy at 48 h post-transfection. Scale bar: 100 μm. (g) Quantification of transfection efficiency analyzed by counting at least 900 cells for each condition. (h) Cell viability obtained by MTT assay. Cells are treated for 4 h with 0.5 mg/mL MTT in complete medium. Then, the absorbance of formazan solution is measured by using enzyme-linked immunosorbent assay. PEI and PS w/o mag (PEI-SPION without magnetic field exposure) were used as control and treated in the same way as their counterparts. PS rot mag indicates PEI-SPION exposed to rotary magnetic fields. Data were shown as mean ± SD of at least 3 independent experiments; ns: nonsignificant, *p < 0.05, **p < 0.01.