Down-regulation of EGFR by siRNA-loaded nanogels. A. Hey cells were examined for EGFR expression by immunoblotting of Hey cell lysates prepared from 24 to 120 hours after the addition of EGFR siRNA-loaded nanogels. Nanogels were loaded with siRNA at a concentration of 16.6 μg siRNA/mg of nanogels, and 1000 μg/mL of the loaded particles was added to 5 × 105 cells. Untreated (UT) cells were set at 100% expression of EGFR. Controls included unloaded/untargeted nanogels (Ng), and YSA peptide alone (YSA). Overall, treatment with EGFR siRNA significantly decreased receptor expression at 48 and 72 hours (*P < 0.01) and also at 96 hours (^P = 0.05). The error bars represent ± one standard deviation about the average value (n = 3). B. An immunoblot from one experiment out of three shows the decrease in EGFR expression over time. Controls are the same as those in (A).