Synthetic hydrogels as scaffolds for manipulating endothelium cell behaviors

Synthetic hydrogels can be used as scaffolds that not only favor endothelial cells (ECs) proliferation but also manipulate the behaviors and functions of the ECs. In this review paper, the effect of chemical structure, Young's modulus (E) and zeta potential (ζ) of synthetic hydrogel scaffolds on static cell behaviors, including cell morphology, proliferation, cytoskeleton structure and focal adhesion, and on dynamic cell behaviors, including migration velocity and morphology oscillation, as well as on EC function such as anti-platelet adhesion, are reported. It was found that negatively charged hydrogels, poly(2-acrylamido-2-methylpropanesulfonic sodium) (PNaAMPS) and poly(sodium p-styrene sulphonate) (PNaSS), can directly promote cell proliferation, with no need of surface modification by any cell-adhesive proteins or peptides at the environment of serum-containing medium. In addition, the Young's modulus (E) and zeta potential (ζ) of hydrogel scaffolds are quantitatively tuned by copolymer hydrogels, poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm), in which the two kinds of negatively charged monomers NaAMPS and NaSS are copolymerized with neutral monomer, N,N-dimethylacrylamide (DMAAm). It was found that the critical zeta potential of hydrogels manipulating EC morphology, proliferation, and motility is ζcritical = -20.83 mV and ζcritical = -14.0 mV for poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm), respectively. The above mentioned EC behaviors well correlate with the adsorption of fibronectin, a kind of cell-adhesive protein, on the hydrogel surfaces. Furthermore, adhered platelets on the EC monolayers cultured on the hydrogel scaffolds obviously decreases with an increase of the Young's modulus (E) of the hydrogels, especially when E > 60 kPa. Glycocalyx assay and gene expression of ECs demonstrate that the anti-platelet adhesion well correlates with the EC-specific glycocalyx. The above investigation suggests that understanding the relationship between physic-chemical properties of synthetic hydrogels and cell responses is essential to design optimal soft & wet scaffolds for tissue engineering