*2.9. Cellular Association with FA-PEG-Modified siRNA Lipoplexes*

The KB cells were seeded in 6-well culture plate at a density of 3 <sup>×</sup> <sup>10</sup><sup>5</sup> cells per well, 24 h prior to transfection. Each siRNA lipoplex with 50 pmol AF-siRNA was diluted in 1 mL of folate-deficient RPMI-1640 medium (50 nM siRNA) supplemented with 10% FBS and then added to the cells. After 3 h incubation, the cells were washed twice with 1 mL phosphate-buffered saline (PBS) to remove any unbound lipoplexes. The amount of AF-siRNA in the cells was determined by examining fluorescence intensity using a FACSVerseTM flow cytometer equipped with a 488-nm argon ion laser. Data for 10,000 fluorescence events were obtained by recording forward scatter (FSC), side scatter (SSC), and green (530/30 nm) fluorescence.
