Optimizing siRNA efficacy through alteration in the target cell-adhesion substrate interaction

The clinical potential of siRNA based therapeutics remains hindered by the challenge of delivering enough siRNA into the cytoplasm to yield a clinically relevant effect. Although much research has focused on optimizing delivery vehicles for this class of molecules, considerably less is known about the microenvironmental influences on the response of target cells to siRNA. The substrate to which cells adhere is one component of the microenvironment that can modulate cellular behavior. Here, we tested the hypothesis that modulating the properties of cellular adhesion substrates can alter siRNA efficacy. Specifically, cationic lipid complexed siRNA particles were applied to U251 cells seeded on alginate hydrogel surfaces with systematic variation in elastic modulus and integrin ligand RGD density. These experiments revealed no change in siRNA mediated eGFP knockdown over the elastic modulus range tested (53 to 133 kPa). However, an eight-fold increase in RGD content of the alginate growth substrate resulted in an increase in siRNA knockdown efficacy from 25 ± 12% to 52 ± 10%, a more than two fold increase in silencing. Our results identify control of the cell-adhesion substrate interaction as a modulator of siRNA protein silencing efficacy.