Intracellular visualization of transfection complexes. Cells were transfected with optimized fluorescently labeled miR/PEI/MNP (20 pmol miR; N/P ratio 7.5; 3 μg/mL MNPs) complexes. miR staining was performed with Cy5 dye (red). PEI was labeled Oregon Green 488 (green). MNPs were stained with Atto 565 (yellow). Nuclei were counterstained with DAPI (blue). Representative images were taken 18 h after transfection using structured illumination microscopy (SIM). Scale bar = 5 μm.