2.8 Cell viability inhibited by NC-mediated siRNA delivery
The inhibition by NC-mediated siRNA delivery was optimized depending on the N/P ratio and siRNA concentration using the viability assay of breast cancer cells. First, MDA-MB-231 breast cancer cells of 5.0 × 103 were seeded to wells of a 96-well plate and incubated at 37oC for 16 hours in a 5% CO2 incubator (Esco Micro Pte. Ltd., Changi, Singapore). For N/P ratio optimization, 10 pmol of CGI siRNA were mixed with the N/P ratio of 1, 2.5, 5, 7.5, 10 for RS peptide and 10, 20, 30, 40, 50 for RT peptide in 100 µL of total volume as described above. For siRNA concentration, 100, 200, 300, and 400 pmol of CGI siRNA was mixed with RS peptide of N/P ratio 5 of and R11 peptide of N/P ratio 20. Then, 100 µL of each solution was added to each well and incubated for 24 hours at 37oC in a 5% CO2 incubator. The same procedure was repeated. 10 µL of CCK solution was added to each well. After incubation for 2 hours, the absorbance at 450 nm was measured by the Epoch2 microplate spectrophotometer (BioTek Instruments, Inc., VT, USA)