Stiffness of polyelectrolyte multilayer film influences endothelial function of endothelial cell monolayer

Endothelialization has proved to be critical for maintaining long-term success of implantable vascular devices. The formation of monolayer of endothelial cells (ECs) on the implant surfaces is one of the most important factors for the endothelialization. However, endothelial function of regenerated EC monolayer, which plays a much more important role in preventing the complications of post-implantation, has not received enough attention. Here, a vascular endothelial growth factor (VEGF)-incorporated poly(l-lysine)/hyaluronan (PLL/HA) polyelectrolyte multilayer film was fabricated. Through varying the crosslinking degree, stiffness of the film was manipulated, offering either soft or stiff film. We demonstrated that ECs were able to adhere and proliferate on both soft and stiff films, subsequently forming an integrated EC monolayer. Furthermore, endothelial functions were evaluated by characterizing EC monolayer integrity, expression of genes correlated with the endothelial functions, and nitric oxide production. It demonstrated that EC monolayer on the soft film displayed higher endothelial function compared to that on the stiff film. Our study highlights the influence of substrate stiffness on endothelial function, which offers a new criterion for surface design of vascular implants.