The effects of nanofiber diameter and orientation on siRNA uptake and gene silencing

While substrate topography influences cell behavior, RNA interference (RNAi) has also emerged as a potent method for understanding and directing cell fate. However, the effects of substrate topography on RNAi remain poorly understood. Here, we report the influence of nanofiber architecture on siRNA-mediated gene-silencing in human somatic and stem cells. The respective model cells, human dermal fibroblasts (HDFs) and mesenchymal stem cells (MSCs), were cultured onto aligned or randomly oriented electrospun poly(ε-caprolactone) fibers of different average diameters (300nm, 700nm and 1.3μm). In HDFs, decreasing fiber diameter from 1.3μm to 300nm improved Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and Collagen-I silencing efficiencies by~3.8 and ~4.4 folds respectively (p<0.05) while the effective siRNA uptake pathway was altered from clathrin-dependent endocytosis to macropinocytosis. In MSCs, aligned fibers generated significantly higher level of gene silencing of RE-1 silencing transcription factor (REST) and green fluorescent protein (GFP) (~1.6 and ~1.5 folds respectively, p<0.05), than randomly-oriented fibers. Aligned fiber topography facilitated functional siRNA uptake through clathrin-mediated endocytosis and membrane fusion. Taken together, our results demonstrated a promising role of three-dimensional fibrous scaffolds in modulating siRNA-mediated gene-silencing and established the critical synergistic role of these substrates in modulating cellular behavior by RNAi.