*2.8. Cytotoxicity by FA-PEG-Modified siRNA Lipoplexes*

The KB cells were seeded in 96-well culture plate, 24 h prior to transfection. Each siRNA lipoplex with 50 pmol Cont siRNA was diluted in 1 mL of folate-deficient RPMI-1640 medium supplemented with 10% FBS, and then the mixture (100 μL) was added to the cells at 50% confluency in the well (final 50 nM siRNA concentration). After a 24 h incubation period, cell numbers were determined using a WST-8 assay (Cell Counting Kit-8, Dojindo Laboratories, Kumamoto, Japan). Cell viability was expressed as relative to the absorbance at 450 nm of untransfected cells.
