Fig. 5

Gene silencing activity and cell viability of fusion peptides: a Target GAPDH mRNA knockdown in HeLa and HaCaT by siRNA/peptide nanocomplexes was verified using quantitative RT-PCR. GAPDH-siRNAs of the final 200 nM concentration were delivered into each of the 1.0 × 10⁵ HeLa cells in a 24-well plate using Lipofectamine™ 2000 as a commercialized positive control, SPACE, R11, S-R7, S-R11, and S-R15 (20:1 N/P ratio) for 5 h. 100 ng of total RNAs isolated from cells were reverse-transcribed into cDNA. 10 ng of cDNA were used for the PCR reaction with GAPDH-specific forward and reverse primers. Relative mRNA expression levels were calculated using the ΔΔCt method based on the housekeeping β-actin expression level. The relative expression levels of GAPDH mRNA were normalized by the mRNA expression of free siRNA. The data represented mean ± standard deviation (*p < 0.05, **p < 0.01, and independent n ≥ 3). b Cell viability of three fusion peptides was examined using a lactate dehydrogenase (LDH) assay. Released LDH activities were measured from 8.0 × 10³ HDFn cells under each fusion peptide at different concentrations (0, 0.0125, 0.025, 0.05, 0.1, and 0.2 mg/mL) in a 96-well plate using an LDH assay. LDH activity of cells treated with each peptide was normalized with the LDH activity without the peptide. The data represented mean ± standard deviation (independent n = 3). The p-value was calculated using a t-test.