Figure 3.

Gene delivery regulated with the distance between islands of RGD peptides (d_RGD), as the total density of RGD peptides was kept constant at 6 × 10⁹/mm². Microscopic images show the decrease in the cellular uptake of the rhodamine-labeled pDNA condensates with d_RGD (a). White lines in photomicrographs represent borders of cells adhered to the gel matrix. The efficiency of gene transfer quantified from photomicrographs was linearly decreased with d_RGD (R² = 0.96) (b). The gene expression level (● in c) and the gene expression level normalized to the average surface area of cells (■ in c) exponentially decreased with d_RGD (R² = 1). Increasing d_RGD also down-regulated the gene expression level in cells cultured within the 3D gel matrix (d). Differences in the values in (b) for cells cultured on gels presenting the largest d_RGD (~ 120 nm) versus those on gels presenting the smallest d_RGD (~ 36 nm) were statistically significant (p < 0.05). The gene expression levels in (c) and (d) were normalized to the value attained from cells cultured on gels presenting d_RGD of 120 nm. Data points and error bars represent the mean and standard deviation from four independent experiments.